About   |   Glossary   |   Site map   |   Help   |   Credits   |   Contact  Home   Glossary   Glossary access time The time required for the memory system of a light control board to receive information and make it available to the board operator. aberration The ability of a simple lens to form a perfect optical image is limited by certain inherent defects called aberrations. chromatic aberration absorption_filter A filter which transmits certain wavelengths and absorbs the wavelengths which are not transmitted, as opposed to dichroic filter which reflect the unwanted wavelengths. filter, dichroic filter AC alternating current accent A light with a distinct intensity, direction or color. accessories Devices and add-on equipment which can be added to luminaires, such as barndoors, iris, gobo, shutters, color frames, color changers. barndoors, iris, gobo, shutter, color, frame, color changer ace A 1000-W fresnel spotlight. fresne achromatic_lens Lens which has been corrected for chromatic aberration and does not split light into colors. chromatic aberration ACL Originally aircraft landing lights. ACLs are sealed beam lamps in parcans, designed for a 28V power supply, used in stage lighting in wattage's of 200, 250 and 600W, where a strong, extremely concentrated beam is desired. ACLs are either connected to a st ACL_strips Strips of ACL lights wired together to create a single intense block of light. Svoboda unit acting_area_light A method proposed by Stanley McCandless. Which involved breaking up the acting area into a number of areas, each of which must be assigned one or more luminaires from the desired angles. Thus a small stage might have six acting areas. Each area with two zone lighting, area lighting adapter A connector, or two connectors joined by a short length of wire, used to connect equipment with different types of plugs. additive_color_mixing Mixing the beams of colored light so that the resultant beam includes the sum of the wavelengths of colors mixed. Any three primary (blue red & green), or spectral, colors can be mixed in various proportions to produce any other color. White light can be subtractive color mix advance_bar A lighting bar hung from the auditorium ceiling . Many older theaters (particularly in the UK and on Broadway) have no provision for front-of-house (FOH) lighting and in recent years have installed an advance bar (usual a truss) above the audience, fairly advance pipe, FOH advance_pipe advance bar air-vents ventilation holes alternating_current AC, An electrical current which constantly reverses itself as a result of reversing electromotive force. One complete reversal is a cycle, and the number of cycles per second is the frequency of the alternating current. The standard frequency of alternati direct current ambient_light General indirect light, produced by reflection from the stage floor or scenery or by scatter from luminaires. ampere (amp) A unit of electric current named after Andre M. Ampere (1775-1836). One volt applied across a resistance of one ohm produces one ampere. Fuses are calibrated in amperes, indicating the amount of current that may flow through them without damage. Ohm's law amperage An analogue multiplexed lighting control USITT protocol for up to 192 signals which are time-multiplexed (split into packets of information sent at alternate times) and transmitted across four wires. analogue control, digital communication , protocol, DMX 512 analogue_control A method of dimmer control where information is transmitted as a continuous electric signal. In most analog control systems each dimmer is controlled by a scaled fader (potentiometer) on the control board which is set at a certain intensity. For example 7 digital control animation_disc A large disc placed in front of a luminaire and rotated by a motor. Animation discs are designed with slots or cut patterns, or are made of painted glass, and give the impression of movement of the light. Used with profile-spots in conjunction with gobos animation wheel gobo animation_wheel animation disc ANSI American National Standards Institute. ASA, ASI angstrom A unit which was used in the past to measure short wavelength radiation. Named after the Swedish spectroscopy pioneer A.J. Angstrom (1814-1874). One Angstrom is a wavelength equivalent to 10-9 meter, (i.e. one ten-millionth of a millimeter). One Angstrom spectrum animation The gradual building up of the illusion of movement from a sequence of static pictures. In film, animation is created frame by frame, by exact timing and choreography of both movement and sound. All film movement is achieved by projecting a fixed number o animation disc A large disc placed in front of a lighting instrument and rotated by a motor. Animation discs are designed with slots or cut patterns, or are made of painted glass, and give the impression of movement of the light. Used with profile spots in conjunction w gobo animation wheel see glossasry entry Animation Disc anode A positive electrode. In electrolysis, the anode attracts negative ions from the electrolysis bath. In an electronic vacuum tube, the anode attracts electrons from the cathode and they flow through the anode and out of the tube. In a battery or primary ce Alzak, battery aperture An opening inside profile spotlights where light from the reflector is concentrated. In a luminarie with an ellipsoidal reflector, the aperture is just before the secondary focal point of the ellipsoid; in a luminaire with a spherical reflector, a condens gate, gobo, iris, ellipsoidal reflector, profile spot apostilb A unit of light measurement used in luminous engineering, which expresses the quantity of light radiated per unit area. One apostilb is the equivalent of one lumen per square meter. lumen, lux appia Appia, Adolphe A Swiss scenographer (1862-1928) whose ideas are among those which form the basis for modern theatrical lighting theory. Appia saw light as a dynamic medium which could integrate all elements of the theatrical production, emphasize the li Craig, Gordon apron stage The part of a stage which projects towards or into the audience. In proscenium stages, the area between the front curtain and the audience. proscenium, thrust stage arc lamp A lamp which produces light when a continuous spark of electricity crosses the gap between two separated electrodes within an envelope containing various gasses. carbon arc, discharge lamps arc light Arc Lamp area lighting Acting Area Light arena theatre A theatre where the acting area is surrounded on three or four sides by the audience, usually sloping up away from the stage. artificial light The first sources of artificial light were candles and oil lamps. In the 19th century gas lighting came into use, as well as the electric carbon arc. With the invention of the incandescent lamp, electric lighting, which was brighter and could be controlle incandescent, discharge lamps asa The American Standards Association ANSI asi American Standards Institute ANSI aspect ratio The ration between the width of a screened image and its height. For instance, the aspect ratio of a television image is 4:3 (four width by three height). asymmetric flood A floodlight with an asymmetric mirror, designed for lighting large flat surfaces such as back cloths. The mirror is curved so that it directs a larger proportion of the light to the area further from the lamp and a smaller proportion directly opposite th Cyclorama Lights auditorium lights House Lights auditorium slots Lighting positions located within the auditorium walls at the sides of the audience. In new theatres, auditorium slots are hidden from the view of the audience. In older theatres, where these positions were not planned in the original architecture, these auto-follow cue A cue designed to be run automatically in sequence with the previous cue. Many computer control boards enable programming of auto-follow cues. The term is also used in manual board operation, where the first cue is given by the stage manager, or taken by automated lights Remote controlled luminaires operated by small motors which move (pan or tilt) either the entire luminaire or a mirror which directs the lightto the stage. Automated lights are usually computer-controlled. Sophisticated automated lights provide remote con DMX, gobo, iris, yoke, intelligent luminaires autotransformer An electrical dimmer based on mechanical control of the current. When the autotransformer, an iron core wound with wire, is connected to an alternating current, back EMF is induced along the wire. A sliding contact along the wire taps off different voltag Bordoni, Variac AV projector (audio-visual) A slide projector. High power projectors use discharge lamps such as HMI or xenon with mechanical dimming devices.The slides can be as large as 24 x 24 cm. Carousel type projectors are smaller and less expensive. They use less powerful inca projection baby Originally slang for a 250 to 400 W plan convex luminaire with a 4 to 5? diameter lens. Now usually denotes a 500 to1000 W Fresnel luminaire with a 6? diameter lens, a standard luminaire in the motion picture industry. Can also used to denote a small vers baby spot Baby backup control board A control board intended to enable illumination of the stage in the event of a failure in the computer board. Ideally, backup control boards should be duplicates of the main control board, following the cues parallel with it so that in case of failure the baffle Pieces of metal placed in the luminaire to prevent light from spilling through ventilation holes in the body of the luminaire. balcony rail A lighting position in front of the auditorium balcony. Instruments are not normally hung from the balcony railing itself but from a cove or pipe below it, out of the reach of the audience. Balcony rail positions provide a shallow frontal lighting angle, balcony spotlight A luminaire mounted in the balcony of an auditorium, generally at the front of the balcony rail. ballast An electrical device which limits the current through the lamp, maintaining a constant direct current. Ballasts are necessary for the operation of all discharge lamps. Some ballasts have additional functions incorporated into them, such as lamp starting, base light 1) In television - a uniform, diffused illumination used to establish a sufficient ambient level of light at the desired lens aperture, for quality type television and film pickups. 2) In theatre - the acceptable base level of unaccented stage illuminatio bayonet base A lamp base with two fins projecting from the sides of the base. The lamp socket has two openings matching the fins, and the lamp is inserted and then turned sideways, locking the fins in place and ensuring that the lamp will lock into a specific position beam The flow of light emitted from a luminaire in one direction. Also used to describe a ray of sunlight. Beam Angle beam angle In theatre, the part of the beam where the candlepower is over 50% of the maximum candlepower is defined as the beam angle of the luminaire. This criterion is used for theatrical and photographic lighting equipment, but the definition of the beam angle ca half-peak angle beam axis If the beam of a luminaire is referred to as an x-y plane, the y axis will define the direction of the beam from the luminaire to the stage. The beam axis can be described as an imaginary line along the center of a light beam. beam light 1) Beam lights were originally developed for outdoor search lighting and have an extremely strong and concentrated beam of light. Beam lights have been adopted and modified for stage lighting, and are particularly popular in rock and roll. Similar in the beam lumens The amount of light (in lumens ) within the beam angle of a luminaire. beam pattern The design of the lamp influences the way the light strikes the illuminated surface. A lamp with a fresnel lens and wide focus has a soft diffuse and even beam pattern as opposed to the oblong uneven pattern characteristic of a PAR. beam projector A luminaire which uses a paraboloidal reflector with the light source at the focus of the reflector to produce a narrow, almost parallel, beam of light. beamlight beam spread Field Angle beamlight Beam Light bed A platform, usually suspended from above, providing lighting positions on motion picture stages. bi-focal spotlight A profile luminaire with two sets of shutters. The first set of shutter is at the gate, the extra set is located beyond the gate and enables soft focused shaping of the beam. binocular vision 1) One of the mechanisms which enables depth perception is the incongruent views our two eyes receive because of their different relative positions in space. 2) The difference in muscle strain involved in both eyes focussing simultaneously n a near or dis black box theater A theatre space with black walls and a black ceiling in which any number of different arrangements of the acting are and audience areas can be set up (an arena stage, a wied or narrow frontal stage etc). Also known as a ?neutral? theatrical space. blending lighting General illumination used to provide smooth transitions between the specific lighting areas on stage. blind editing A function in most computer control boards which enables plotting or editing a cue while a different lighting state is active on stage. blind mode Blind Editing blind plotting Blind Editing blinders Lights focussed on the audience. The blinders are brought up to blind the audience during scene changes, in order to ?hide? the change from the audience. Usally used in open air theatre. B.O. blackout 1) An abrupt cue to complete darkness 2) A button on control boards which 'blacks out' all board output boom A vertical pipe hung from the bars or pipes, from which luminaires or bopom arms can be hung to enable a lower lighting angle than that of the bars. Boomerang boomerang A box attached to luminaire, holding various color frames which can usually be changed by electrical or mechanical devices. boom arm A short pipe extending sideways from a boom, from which luminaires can be hung borderlight A striplight mounted above the acting area. X-Ray bordoni control A multiple channel autotransformer dimmer. In borodini control systems, one large transformer was used for all of the circuits, and each circuit had its own secondary winding which slid in and out to tap off different voltages. ?Bordonis? had between 6 an bounce cloth Reflection Cloth bounce lighting Light directed at and reflected from a large diffusing surface, used as soft indirect light. box boom A lighting position in the front side boxes of older theaters, providing front-of-house (FOH) side lighting angles. Today this term can also refer to any FOH side-lighting position. auditorium slots bracket A piece of metal attached to the wall, ceiling or floor, for mounting luminaires. brailing Pulling scenery hung from a pipe, or the pipe itself, upstage or downstage by attaching a rope to the pipe ends and tying it off at the sides. Pipes are brailed when the elements hung on them are too close to each other to enable movement of one of the el bridge A narrow platform suspended over the acting area. Luminaires and projection devices mounted on the bridge are accessible during the performance. broad Slang for a wide angle floodlight. brute Slang for a 225 ampere DC high intensity carbon arc luminaire with a 24? diameter Fresnel lens. built-in cue A method of transition from one lighting state (preset) to another, used on some manual control boards. The new preset can be brought up while the previous preset is still at full intensity, thus enabling different in and out times of the lighting cues. crossfade bunch light An early type of floodlight where ten or twelve low-wattage lamps were placed in front of one reflector. cable clamp A metal clamp fastened to the end of a cable to prevent fraying and improve the electrical connection. cameo A lighting state common in television studios when only the foreground is illuminated, and the background is left black and unlighted. Limbo camera light A lighting instrument mounted on a camera. This enables lighting directly in line with the optical axis of the camera lens, usually to provide eye light. carbon arc The carbon-arc lamp was the first practical electric lighting device used on stage. The first controlled electric arc discharge between two carbon rods was produced by Sir Humphry Davy in 1807, and this method of light production was initially used for se CCT Correlated Color Temperature channel access The manner in which changes in the intensity of control channels are made on computerized control boards. On almost all boards, lights are brought up by calling up a channel number or numbers and assigning the intensity. Most computer boards provide chann digitizer chaser 1) Channels or groups of channels which are sequentially switched on and off in a continuous loop, by a computerized control board. The speed of most chasers can be controlled, and some boards have numerous chaser options and can run multiple chasers simu check 1) Low, barely visible dimmer intensity. Used to verify dimmer operation without the light being visible on stage. 2) A term denoting a decrease in dimmer intensity choke An iron core with a spiral of coil wound round it. When an alternating electric current is passed through the coil, magnetic flux within the core induces ?back EMF? in the coil in the opposite direction of the current. Used in three different types of dim choke dimmer Reactor Dimmer chroma key A special effect commonly used in television. The object or person is photographed on a monochromatic color background (usually cobalt or deep ultramarine blue). A differnt background is electronically inserted in place of the background monochrome surfac chromatic (color) aberration Aberrations chromatic adaptation Color Adaptation chromatic (color) image defects Aberrations chromaticity Refers to a combination of the hue and saturation of colored light, without taking into account the intensity of the light. CIE The standard chromaticity diagram - a graphic method of describing the color of light, devised in 1931 by the Commission Internationale de l'Eclairage (hence CIE). The graph describes light in terms of its wavelength, saturation, and human visual sensitiv circuit breaker An electric switch that automatically breaks (opens), an electric circuit when the current exceeds the defined maximum. Like a fuse, a circuit breaker interrupts the current in the circuit, but unlike a fuse, it can be reset (closed) after it has tripped clear 1) An instruction for all backstage personnel to leave the stage as the scene is about to start. 2) Removal of props from the stage. 3) An indication on a lighting plot that a lamp has no color filter, i.e. is clear (for short CL, other terms used: NC for close to spot Transition from a widely lit stage to a concentrated and defined area. coherent light A beam of light all of which is of one wavelength and polarization, and the rays of which are in phase (i.e. the peaks and troughs of the electromagnetic radiation are always similarly spaced). This uniformity causes the beam to be of a much greater inten color and music A system in the field of the psychology of color vision, which defines a corresponding scale of color and music. The relationship between tones and colors is: do (C) = deep purple; re (D) = purple; mi (E) = red; fa (F) = orange; sol (G) = yellow; la (A) = color changer A device placed in the color frame runners in front of a luminaire, enabling remotely controlled changes of the color filter. There are two different methods in which the color is changed. Semaphore color changers have four or five different filters which Color Magazine color compensating filter Color Correction Filter color constancy The psychological tendency to perceive colors as we are ?programmed? from experience to expect them to be rather than as we actually see them. This often causes us to compensate mentally for changes in the lighting. When we see a tomato in blue light we s color contrast Color contrast is used to aid visibility and to add visual interest. The strongest color contrast is produced by the juxtaposition of two colors which are furthest apart on the color wheel or on the spectrum, i.e. complementary colors. The greater the sat color filter A plastic sheet (media) placed in front of a luminaire in order to change the color of the beam by absorbing certain wavelengths and letting other wavelengths through. For instance, a red filter lets only the red wavelenghts through, absorbing all other w Dichroic Filters color intensity Saturation color magazine Several frames of color filters which can be alternately inserted in front of the luminaire, found in follow spots and in semaphore color changers. color media Color Filter color medium Color Filter color mixing The combination of different colors of light and/or surfaces in order to achieve a wider range of colors. Color mixing can be additive or subtractive. See also additive mixing, subtractive mixing, color filter color perception Our psychological reaction to color, the way color affects us or way in which points or homogeneous patches of light appear to a subject. Color perception can be described in terms of hue (red - how reddish is the apple, etc.); saturation (from vivid, pur See section on light and vision color rendering index Color Rendering Index (Ra) index compares the effect of light emitted from a given light source to light emitted from incandescent sources with the same color temperature. Used to describe the visual effect of light on colored surfaces. color saturation The extent to which a color is spectrally pure, not mixed with white or with any other color. Also known as color value Hue, Brightness, Color Perception color temperature The temperature, in degrees Kelvin, at which a black body emits radiant energy of a cetain color when it incandesces. As the black body heats up, the color of the radiant energy will change from red to white to blue white. Specific colors of light sources color value Color Saturation color vision Objects look colored because of the way they reflect light. White light from the sun or an artificial light source such as a lamp contains all colors of the spectrum. When white light falls on an object, the object reflects only certian wavelengths. Grass color wash A wash of light over the stage in a specific color. color wheel 1) In theatrical lighting: a wheel divided into sections of different colored media, placed in front of the lumianire, which can be rotated manually or by motor in order to change the color of the light. 2) A two dimensional model, originally created by colorimetry Measurement or determination of color by quantative chemical analysis. The color of a liquid is compared with standard colors determined in colorimetry. colouvred fresnel lens A fresnels lens inwhich the risers of each colouver are painted black to reduce the scatter or spill. compact filament A filament shaped in a condensed manner in order to achieve as small a source of light (as close to the ideal point source of light) as possible, in order to obtain a better optical performance and a higher color temperature. company switch A disconnect switch and power source for portable lighting equipment compartment floods A luminaire which includes several floodlights wired in three or four circuits. Usually used to wash the stage or background with different colors. complementary colors 1) In light - a pair of primary and secondary colors in the additive color mixing system which when combined will make white light. The pairs are: Primary Secondary Red Cyan Green Magenta Blue Yellow 2) A pair of colors opposite each other on the color wh complementary tints complementary tints Visibility can be improved by lighting the actor's face with unsaturated complementary colors from different angles, for example very pale blue from one angle and very pale yellow or straw from the other. compound lens A lens made of more than one type of glass, e.g. Crown and flint, to minimize color aberrations. compton organ An organ console adapted by Frederick Bentham to serve as a lighting console. The stopkeys selected the channels, and dimmers were driven by motors on a remote dimmer bank. Speed was controlled by a foot pedal. computer board An advanced lighting control board, based on computer technology, with a wide range of functions including intensity changes, channel patch, chasers, multifades, scroller control, fade in and out, automized sequences and much more. Diffferent computer boa computerized lighting control Computer Board concert border A borderlight mounted immediately behind the proscenium arch. condenser lens A short focal lens, placed in a projection system (a projector or a coplex profile spot) which directs light from the lamp into the gate or film aperture and into the projection lens. conducter Electric Conductor conduit A pipe or rectangular tube, usually made of plastic, providing a protective coating or shield for electric wires or cables. cones The cells of the retina responsible for color vision. The cells (receptors) in the retina responsible for diurnal (Photophic) vision and color vision. The receptors responsible for nocturnal (Scotopic) vision are called rods. See section on Light and Vision connections list A list indicating to which electrical input and dimmer each instrument in the rigging of a show will be connected, and which control channel will control each instrument. The connections list can be sorted by control channel, hook-up, dimmer or instrument connector Electric Connector console Lighting Control Console contour light Back Light contrast ratio The ratio between the highest luminance and the lowest luminance on stage at a specific point in time or during a scene. control board An electrical panel with dimmer controllers, faders (potentiometers), nondim switches , and other functions, used to control the light on stage. Lighting Control Console, Dimmer Board control booth Lighting Control Booth control cable A cable used for transmitting control signals, usually with a control signal of 12V or a DMX signal. Control cables need not be thick, but they must be well screened against interference. USITT standard for DMX512 specifies a shielded, twisted-pair, low-c control channel A number used in computer control boards to identify the controlled unit. A control channel can operate one or several dimmers; instruments such as color scrollers; one parameter of an intelligent luminaire or a yoke; or a motor, smoke machine, strobe, et soft patch, channel access control channel number A specific number designating the control channel to which each instrument or group of instruments on the lighting plot will be connected. See also Soft Patch, Control Room, Lighting Control Booth control signal A signal sent from a lighting board through a cotrol cable to the dimmers. In older, manually operated boards, the control signal is an electrical 12VDC pulse. In computerized lighting boards the signal is a very low voltage and can be either analog or di controller A slide on a computer board which can be programmed to control a channel, group of channels, cue or chaser. Submaster cookie Cucoloris cool color A color in the range of green-blue-violet. Other colors, for instance, certain pinks, may seem cool depending on their proximity to warm colors. Light sources with a high color temperature generate a cool (white or bluish) light. Warm Color cool reflector Dichroic Reflector correction filters Color Correction Filters correlated color temperature Used to describe the color temperature of light sources which are not incandescent, such as discharge lamps. These sources do not have a continuous spectral light output, although the light appears to the eye to have a color similar to a specific color te cosine law An equation which enables calculation of the illuminance of a surface which varies in accordance with the cosine of the angle of incidence. The cosine law and the inverse square law are the two fundamental laws of photometry. costume designer The person in charge of designing the costumes for the show. In some cases, the scenic designer is also the costume designer. count A method of indicating the length of a change in the lighting state on stage, based on one second units. counter-key Illumination of a subject from a direction opposite to that of the key-light. Also known as Fill Light. coupling Pairing cove A front of house (FOH) lighting position, recessed in the auditorium ceiling. cp candlepower Craig Edward Gordon, (1872-1966) A British designer, director and theoretician who saw the art of the stage as a synthesis of all theatrical elements, which ought to be created by one person. His theories he influenced the development of the function of directo cross connect system A connecting system which enables studio outlets to be temporarily connected to various dimmer and non-dim circuit outputs. Patch Panel, Selector Switch System cross-bar interconnection A method of connecting electrical circuits to dimmers by a board of vertical and horizontal busbars. The vertical bars are connected to the circuits and the horizontal bars to the dimmers. By inserting a pin at the desired intersection, or moving a slide Patch Panel cross-fade A method of transition from one lighting state to another on a manual control board. The new lighting state is brought up while simultaneously the previous state is brought down. A common variation of this system, often found in computerized control board cross-fade profile The graphic curve describing the manner in which a crossfade is accomplished. Most cross fade profiles are linear so that the light changes uniformly with respect to time. Sophisticated computer boards enable programming or selection of different cross-fa crosslighting Illumination from two sources on opposite sides of the subject. Often different color media are used in the luminaires for a given area in order to give an illusion of a shadow while providing sufficient illumination for good visibility. cross section A plan showing the set, lighting and/or stage layout perpendicular to the stage floor along a line running from SL to SR, from SR to SL, from DS to US or any other cross section necessary to understand the scenery, lighting or stage layout. Cross sections CRT A Cathode Ray Tube (CRT) is an electron gun which produces a beam of electrons that pass through horizontal and vertical deflection plates and then falls upon a luminescent screen. Electric potentials applied to the deflection plates are used to control t CSI CSI stands for Compact Source Iodine. A metal halide discharge lamp with a color temperature of about 4200OK, used primarily in follow spots. CID, discharge lamps cucoloris An opaque material with a cutout which allows light to pass through the cutout area, project forms such as cloud formations onto scenery, backdrops or a cyclorama. Also called cukes or cookies cue An event in a production that is the signal for a specific action (for instance a specific line of text or the exit of an actor), or a signal given (by the stage manager) in order to cause such an action. The response to such a signal is also called a cue cue count The amount of time it takes for a lighting transition to occur, normaly in seconds. cue lights Lights with which the stage manager can signal a cue. Cues are usually given verbally with headset or intercom but cue lights are used as a backup system or where a verbal system is unavailable or inappropriate. Generally red lights are used for 'standby' cue list A list of the cues for the play, when they happen and what the lighting change is. The Stage Manager is usually responsible for the Cue List. cue sheet A written plan for operation of the lighting. With manual boards, clarity and conciseness are crucial. A cue sheet specifies for each cue the number of the cue, manual operations necessary (crossfade, etc.), the timing of the cue, which dimmers are active cue synopsis A written list of lighting cues including their position in the script, timing, and nature of lighting change. The designer uses the cue synopsis as an aid when plotting the show. The board operator or stage manager use the cue synopsis as an aid to opera current flow Entry Amperage current surge Electric Current Surge curtain dressing Curtain Warmers curtain warmers Light washing the front curtain. Before the beginning of a show or act the customary routine is: house lights to half, curtain warmers on, house out, curtain warmers out, thus bringing the audience into the atmosphere of the show. cut The instantaneous execution of a cue, also called a Bump or Snap. cut-off angle That area of a light beam where the light is less than 1% of its maximum intensity. cutter Gobo cyc strip A unit of three or four compartmented cyclorama lights, wired in three or four circuits for different color washes. Cyclorama Lights earth ground Edge Effect An increased emphasis of outlines common to the imageorthicon Edison, Thomas Alva (1847-1931) 19th century American inventor whose major contributions to lighting included the incandescent lamp (1879) (along with Swann in England) and the central electric light-power station (installed 1882), with steam-driven generators which could power 7,200 l effects machine projection spotlight (generally a PC with additional objective lens) with motor-driven disc in front; discs, usually of glass, are available with images of clouds, rain, snow, etc. Effects Projector A scenic projector, often involving multiple slides and/or motion Effects Machine Efficacy The effectiveness of a light source in converting electric power(watts) to luminous flux (lumens) expressed in lumens per watt (LPW). In the pat, this concept was called luminous efficiency. Lumens Per Watt Efficiency The ratio of a specifically designated output flux (lumens) to the flux (lumens) generated by the lamps (the efficiency of a 1000 watt FEL lamp which emits 27,500 lumens, is 27,5 lumen per watt of power), in a luminaire; e.g. beam efficiency, field effic electric arc Electric arc or arc discharge, is a continuous electrical conduction in gases between two separated conductors. It is characterized by high current density and relatively low potential difference, or voltage. (In contrast, a spark is a relatively brief electric capacity That property of a system ofelectrical conductors that enables it to store electric charge when a potential difference exists between the conductors. Unit of measurement is the farad. capacitance Electric circuit path for transmitting electric current. An electric circuit includes a device that gives energy to such as a battery or a generator; devices that use current, such as lamps or motor; conductors, such as copper or aluminum wire, to transport the electrical electric conductor anything which will carry electric current. Metals, tap water and the human body will all conduct electricity; in most systems insulated metal wire is used. electric connector device used for electrical connection between two separate conductors. This may be a plug or socket with two or three pins: live, neutral, and usually earth as well. Multipin connectors such as the popular Socapex family are used with multicore cable to c amperage electric current surge sudden abnormal rise in current voltage electric distribution electric load the amount of instruments connected to a system, and limited by the load capacity of the system; for instance a dimmer with 10 amp fuses will carry a 220 volt load of up to 2 kilowatts. Older dimmers such as rheostats were load sensitive and if not loaded electric pole one of the two terminals of an electricity-generating system such as a battery or dynamo. electric power rating Electrical systems are rated and fused for the maximum amount of load they can bear, expressed in amps. (???is that what you meant?) electrical isolation insulation Electrician The stagehand responsible for execution of production lighting. electricity atomic particles bearing opposite charges repel each other; this property is used in the form of electric current to do work (generally to produce light, in theater), as the movement of electrons through resistive material causes energy to be emitted in t electrode electrode terminal, usually in the form of a wire, rod, or plate, through which electric current passes between metallic and nonmetallic parts of an ELECTRIC CIRCUIT. The electrode through which current passes from the metallic to the nonmetallic conduct electroluminescence certain substances when bombarded with electrons emit light. electromagnetic impedance opposition of a circuit to the passage of current. In a DC circuit this is the resistance; in an AC circuit the reactance too must be taken into account (the square of the impedance equals the sum of the squares of resistance and reactance) electromagnetic interference interaction of two or more wave motions; when the crest of one meets the trough of another the waves cancel out, whereas when two crests meet their effect is doubled. This may be observed when light from two slits is projected at a screen: rather than a electromagnetic spectrum the range of wavelengths or frequencies of electromagnetic radiation, from radio waves at the longer end to gamma rays at the shorter. Visible light is a small part of the spectrum, ranging in wavelength from about 350 to 750 nanometres. electromagnetism magnetism produced by an electric current electronic control control devices with electronic components. These may be dimmers with components such as the SCR or triac, or lighting control boards which are sophisiticated computers. Elex A term used to specify when a general theatrical term relates to lighting. For example, an elex cue or an elex pipe. Elizabethan Theatre English theatre in the 16th century, during the reign of Queen Elizabeth. Includes Shakespeare. electronic dimmer Dimmer using electronic components to controlthe passage of electricity to the lamp. ellipsoidal reflector .Reflector in the shape of an ellipsoid, a solid geometrical form with two foci. A lamp at the focus closer to the reflector will have its light reflected back through the other focal point. Ellipsoidal Spotlight A luminaire embodying a lamp, an ellipsoidal reflector, a framing device, and a single or compound lens system, together with provisions for accommodating a pattern hold and patterns. emergency lighting A lighting system generally fed from a low voltage generator to ensure sufficient light for public safety in the event of a power failure. entertainment control show control Entrance 1) The various places from which actors can enter the stage (doors, wings, openings, stage apron and so on. 2) A particular entrance of a particular actor. envelope lamp envelope equal energy spectrum (*9600K) equal energy white see equal energy spectrum Equipment List A list of the kind and quantity of equipment necessary for a particular show, sorted by types. Exit 1) The various places from which actors can leave the stage (doors, wings, openings, stage apron and so on. 2) A particular exit of a particular actor. Expressionist Lighting A lighting style associated with Expressionist Theatre. Expressionist lighting enables the actor?s face or body to be lit and emphasized from unconventional angles, often causing distortion, with harsh contrasts between light and shadow, and excessively s ExpressionistTheatre Expressionist art and theatre began to appear in Germany around 1910, and advocated extroverted expression of the internal emotional impact of the play and the subjective reactions of the characters. The espousers of expressionist theatre claimed that ex extension extension cable extension cable cable used to feed electricity from socket to lighting instrument. eye light see inky-dinky Fade In A gradual increase of lighting levels Fade Out, Crossfade Fade in The gradual dimming up of a light(s). Fade Out The gradual dimming out of light(s). Fader A term sometimes applied to master dimmers controlling many dimming circuits. Fay light A luminaire that uses incandescent parabolic reflector lamps with a dichroic coating to provide 'daylight' illumination Fade to Black A decrease of lighting levels terminating in a blackout Fade Out, Crossfade Field Angle Those points of the candlepower curve where the candlepower 10 per cent of the maximum candlepower define the field of the luminaire. The included angle is defined as the field angle. Filament Alignment In PAR instruments the bulb (sealed beam) can be rotated so that the oval shaped beam is aimed in different directions. This can be referred to as NS or EW orientation, or ?length? or ?width? orientation. Diagram, photo Fill Light Front light from one side which fills in shadows, balancing the key light from the opposite direction. Photo, Diagram, Back Light, Top Light, Side Light Fill-Light Supplementary illumination to reduce shadow or contrast range. Film Chain A television camera designed to accept projected images from various motion picture and slide film formats for display into the television system. Film Speed A measure of the film sensitivity to light, generally in numerical terms of ASA exposure index. More sensitive (faster) films have higher numbers, and the total required exposure is less. Filters material placed in front of an instrument to color or deffuse the beam. In theatrical lighting the accepted means of achieving colored light Is filters mode of plastic (polyester and polycarbonete), gelatine, ordinary glass, or heat resistant glass (Pyrex First Evening The first show held in front of a paying audience Premiere Five K A 5000 watt Fresnel Spotlight. Fiver A 5000 watt Fresnel spotlight. Fixture A name applied to luminaires. Flag Opaque material placed in front of a light source to produce a shadow in the area illuminated. Gobo Flipper Brain Door Flood Spread of the light over a large area. This term is used both to describe the character of the light and in focusing, to indicate concentration of the beam in a Fresnel or PC instrument. Flood can also mean a wash of light over the entire stage or over a Wash Flood To adjust a luminaire usually by moving the lamp closer to the lens; enlarging the diameter of the beam of light emitted. The widest field of illumination from a luminaire. Floodlight A luminaire consisting of only a lamp and reflector with fixed spacing; generally, the reflector has a diffused finish and is often physically large in size. Fluorescence The property of some substances to absorb ultraviolet energy and emit visible light of various colors. Ultraviolet Flux A measure of the amount of light. The unit is the lumen.. Fly To lift scenery or equipment above the stage floor (and usually out of view) by means of lines from the gridiron. Focal length Distance between a particular point of a lens or reflector and the focal point. For simple lenses in lighting instruments it is usually adequate to measure this distance from the center of the lens. Focal Point The small region where a lens or reflector concentrates all light rays received from a distant source of light. Focus Charts Charts indicating the focusing of each instrument or group of instruments. Can be graphic, textual or a combination of both. Examples of different approaches to focusing charts. Focus In addition to its optical meanings, focus is used as a verb to indicate the aiming and adjusting of a luminaire. F.O.H. Front of House - the hanging or rigging positions or the instruments hanging in such positions, located in the auditorium area (above the audience in bridges, from the sides of the auditorium or in other positions). FOH Spots (Front-of-House) Luminaires mounted in auditorium or front-of-house positions. Beam Light, Rail Light, Balcony Spotlight Follow Spot A light power, narrow beam spotlight suited for long throws (typically 100 to 300 feet), generally with iris, shutters, color boom, and other controls. It is designed for hand operation to follow the movement of performers. Footcandle A unit of illumination. 1 fc=1im/ft2. Footlambert A unit of luminace. A diffuse surface emitting on lumen per square foot has a luminance of one fL. Footlight 1) Light from the floor, aimed at the actors. Used to achieve a dramatic and unnatural quality of light. 2) Fixtures used in theatre from the advent of the use of artificial light. These fixtures were placed at the front of the stage apron, throwing ligh Diagram, photo, Toplight, Backlight, Sidelight, Frontlight, Crosslight Footlights S striplight mounted at floor level along the front of a stage. Fresnel The French physicist Augustin Jean Fresnel, b. May 10, 1788, d. July 14, 1827, made fundamental contributions to theoretical and applied optics. Partially anticipated by Thomas YOUNG, Fresnel rejected the view derived from Newton that light consists of ma Fresnel Spotlight A luminaire embodying a lamp and a Fresnel lens, with or without a reflector, which has a soft beam edge. The field and beam angles can be varied by changing the spacing between the lamp and lens. Fresnel Fringe Light Back Light Frontlight Light coming from the direction of the audience and lighting the actors when facing the audience. Diagram, photo, Toplight, Backlight, Sidelight, Footlight, Crosslight Front Lighting Lighting from the general direction of the viewer. Also , FOH Lights. Frost One of a series of color media that is translucent but colorless, used to diffuse light. Funnel Metal tubes of various sizes that can be mounted on the front of spotlights to control stray light. On certain instruments a funnel can be used to reduce beam size. High Hat, Snoot, Top Hat f-Number The f-number of a lens is the ratio of the focal length to the lens diameter. Lenses of large diameter have small f-numbers and hence greater light-gathering power than lenses of small diameter or large f-number. Filters material placed in front of an instrument to color or defuse the beam. In theatrical lighting the accepted means of achieving colored light Is filters mode of plastic (polyester and polycarbonete), gelatine, ordinary glass, or heat resistant glass (Pyrex) Gaffer In motion picture usage, chief set electrician. Gang Connecting more thane one instrument to stage circuit Gel Color Media General Illuminations Diffuse illumination of large areas with floodlights or striplights. Ghost Phantom Load Globe An incandescent lamp. Gobo In theatre, a metal cutout pattern of suitable size to fit in the holder or aperture of an ellipsoidal reflector spotlight. In motion pictures, it is a flag, usually opaque, that can be made with diffusing material. An opaque diffusing cookie. Cucoloris, Cookie Ground Row Lighting strips aimed up from the base of a cyclorama or drop. The masking piece concealing these strips. law of reflection The law of reflection states that the incident ray, the reflected ray, and a line perpendicular to the surface at the point of reflection (called the normal) all lie in a common plane and that the angles made with the normal by the incident and the reflec Index of refraction. When a ray passes from a medium of low density to one of higher density, such as from air to glass, the relative index is greater than unity, and the ray is refracted toward the normal. Conversely, if a ray passes from a medium of high density to one of l Geometrical optics The fundamental concept of geometrical optics is the ray, which may be defined as the path along which a light wave propagates. The three basic laws of geometric optics are the law of rectilinear propagation, the law of reflection, and the law of refracti Genre The thematic form of a show. Common dramatic genres are comedy, tragedy and melodrama. Common genres in dance are ballet or modern dance. Grid 1) An area over the stage tower made of iron grating, sometimes used to hang special items, scenery or lighting instruments, pulleys etc. The grid is strong enough to hold heavy weights and to support crew members walking on it. 2) An array of metal pipes Ground Plan A scale drawing (usually 1:20, 1:25 or 1:50) indicating the exact location and size of all scenic elements on the stage. The lighting plot is based on the layout and on the Ground Plan. The Ground Plan should also include relevant cross sections. Layout, Legend, Cross Sections Hair Light Back Light Half Scrim Scrim half-peak angle That part of a light beam where the intensity is half of the peak intensity. Halo The black aureole surrounding excessively bright regions and vice versa in a television picture, characteristic of the image-orthicon. Halo Light Back Light Halogen Halogen - chemical, one of the five nonmetallic chemical elements that make up the halogen family are fluorine, chlorine, bromine, iodine, and astatine. Most of the halogens are found in relatively small amounts in the Earth's crust. Halogen Cycle When the filament is heated to a high degree, the tungsten evaporates and reacts chemically with the iodine gas (halogen gas) inside the bulb to produce tungsten iodide near the bulb wall. The tungsten iodide particles are moved by convection within the b Hanging Positions The array of pipes (known as elex pipes), ladders, balconies, FOH positions and bridges on which the lighting is rigged. In smaller theatres where there is no stage tower and no pipes, there is normally a grid. Hansen cloth Hansen gauze Hansen gauze A thick gauze used as a transparency when the picture on the gauze itself should be more dominant than that which is revealed behind it. May also be used as a backcloth. Hard Glass Halogen Lamp A tungsten -Halogen lamp with a bulb of hard glass rather than of quartz or vycor. Due to hard glass fabrication techniques, these lamps generally cost less than a similar tungsten halogen lamp and will have nearly equivalent performance. They are usually Hard Light A light that produces hard or sharply defined shadows. haze A very light fog used primarily to make light beams visible Heat Filter A filter which transmits visible light and either absorbs or reflects infrared in order to reduce the heat of the light beam. heat shield heat filter heat sink Metal formed in a heat dissipating shape, often in the form of fins. Hertz(HZ) Unit of frequency, cycles per second. HID Lamps High intensity Discharge Lamps; general lighting lamps of the mercury, metal halide, and high pressure sodium types. High Hat Funnel High-Key Lighting A type of lighten which, applied to a scene, is intended to produce a picture having gradations falling primarily between gray and white; dark grays and black are present but in very limited areas. Intense, overall illumination. In motion pictures, high l high-side light Side light from above, a basic angle in classical dance lighting, used to define contour and add color while preserving some visibility highest-takes-precedence A principle used in lighting control where a channel appears at two or more different levels (on two presets or controllers, for example) and the highest level is transmitted to the lamp. As opposed to ?latest takes precedence? which is more useful for s Highlight Backlight, toplight or sidelight (or any combination of these) which creates a contour of light round the actors, helping to separate them from the background. HMI (Hg, or mercury; Medium arc; Iodide) a type of high-intensity discharge lamp with a multiline spectrum and color temperature of betwen 5600K and 3200K depending on lamp manufacture. In stage lighting these lamps are found in follow spots, slide projectors hoist lifting apparatus hologram the photographic record containing the information to produce a three-dimensional holographic image. holography a method of reproducing three-dimensional images using coherent light and photographic film or plate. A beam of coherent (laser) light is split in two. One (signal) beam is diffracted by the object to be reproduced on the plate. The other (reference) beam hood Metal tube which can be mounted on the front of some luminaires to control unwanted spill light. May also refer to the outer metal covering of a luminaire. hook clamp hook-shaped clamp for hanging an instrument on a lighting bar. Hook Up List A list detailing the quantity, hanging position, hook up, dimmer, control channel and accessories of the instruments. This is another form of organizing all information appearing in the Lighting Plot. Hook-up Hook-up List A list organized according to instrument numbers, indicating the type of instrument, electrical power, focusing (function), filter color, dimmer and control channel of each instrument. Hook-up Plan Based on the lighting plot, the Hook-up Plan indicates where each instrument will be hooked up and the length of cables required to connect each instrument to the electrical input and to the dimmers. Hook-up List horizon German term for sky cloth, occasionally used to refer to older type of cyclorama floods with linear 1K tungsten lamps. Hot Front An electrical panel or switchboard with exposed current carrying parts. Hot Mirror A dichroic coated surface which transmits light but reflects infrared so that the transmitted beam contains less heat. hot patching Patching load to dimmer while the circuit is live. hot restrike time Discharge lamps must cool down for a few minutes to allow the internal pressure of the lamp to reduce to a level where conduction can occur. However in ?hot restrike? lamps a high voltage (about 40,000V) is applied to overcome the high internal pressure a hot spot Brightest part of light of a spotlight. Fresnels with tight focus have a distinct hot spot surrounded by weaker light, and when the focus is flooded the light distribution evens out and the hot spot disappears. hot-cathode lamp Discharge lamp which unlike the earlier cold-cathode could operate at mains voltage. Metallic substances such as ?thoriated tungsten? were heated to incandescence and produced electronic activity in the tube which caused the gas within the tube to emit li House Board A fixed switchboard serving the permanent equipment in a theatre. House Electrician The electrician employed by the facility (theatre arena, etc.) who is in control of audience lighting and performance electrical equipment. House Lights A general lighting system permanently installed in the audience area of either a theatre of studio which provides sufficient illumination for safe movement in the area. HPS (high-pressure sodium) lamp Discharge lamp filled with sodium at a high pressure. As pressure is increased additional parts of the spectrum are emitted as visible light. Its efficacy of about 100 lm/W is less than that of low pressure sodium lamps but the color rendering is far su Hue The color quality identified by color name, such as ?red? and ?blue?. This is determined by its wavelength. ideal radiator blackbody IGBT (insulated-gate bipolar transistors) semiconductor dimming device which uses reverse phase control; that is, it turns off the waveform at a specific point rather than turning it on as does the SCR. The absence of a sharp turn-on spike eliminates electromagnetic noise and therefore the need MOSFET, SCR ignitor Discharge lamps are ignited by applying a high voltage (5000-15000V) across the electrodes to break down the resistance between them so that the gases inside the lamp may start conducting; after the arc has struck a choke or electronic ballast is used to illuminance The luminous flux falling on a surface per second, measured in lux (lumen per square meter). Illumination General-synonym of lighting. Specific- the amount of light (flux) per unit area incident on a surface. The unit is either the footcandle or the lumen per square foot.. illumination level illuminance image the representation of an object produced by mirror, lens or other optical system. Images are defined as real or virtual. A real image is formed at a point through which the rays of light entering the eye have actually passed. A virtual image appears to ha Image retention A vidicon phenomenon also referred to as sticking, trailing, or lagging; occurs with rapid motion of the actor or the camera and is especially noticeable at low lighting levels. impedance electromagnetic impedance incandescence The emission of light by a substance caused by raising it to a high temperature incandescent burner Welsbach burner incandescent filament lamp A glass envelope containing a tungsten filament which when electric current is passed through it heats up and emits light. The glass is filled with an inert gas to prevent filament evaporation, or in the case of tungsten-halogen lamps the halogen gas exte independent A circuit on a lighting board not subject to master and blackout switches or controls. independent switch An independent circuit on a lighting board, generally a non-dim channel. indirect light 1) Light which is spilled sideways from a luminaire such as a fresnel, and often undesired and controlled by barndoors 2) Light reflected from a surface rather than directly transmitted infinite presetting One of the revolutionary possibilities with the development of computers for lighting control was the practically unlimited amount of lighting states which could be plotted, preserved and operated in a show. infrared Electromagnetic radiation with wavelengths longer than red light. In some theaters infrared radiation is used with appropriate cameras and monitors to allow the stage manager to ?see in the dark? and know when a scene shift or other dark transition is com inhibitor Overriding controller which prevents specific channels from being live although they are present in another active controller. Inky A small Fresnel spotlight with a 1.5-to 3-inch lens diameter. Also any incandescent luminaire. Interference In physics, Interference occurs when identical waves of light meet so that they are either in phase, with the crests of each wave matching, or out of phase. with the trough of one wave meeting the crest of another. inrush current When incandescent lamps are switched on the current flowing through a cold filament may be up to 15 times greater than the normal current; this is because cold tungsten has a low resistance, but when the filament heats the resistance increases and curren Instrument A name applied to theatrical type luminaires. Instrument Any professional lighting source. Spot, Lantern, Profile, Fresnel, Parcan, Iris, Flood Instrument Number A specific number designating each instrument on the lighting plot. Example instrument schedule British term for hookup list: a list of instruments used in the show specifying their channel number , dimmer, position, type, color filter and intended focus or effect. insulation Prevention of passage of electric current. Also refers to insulating material, such as the plastic envelope surrounding conducting wires. intelligent dimmers interactive dimmers intelligent light Term used to refer to computer-controlled luminaires with remote control of position, color, focus and other parameters of the light. Intensity A measure of the ?strength? of a light source in a particular direction.. Intensity is independent of the distance from the source. The unit is the candela. Also see Candlepower. Intensity Distribution A graph or diagram that describes how the intensity of a source varies with direction. intensity distribution diagram Intensity distribution graph interconnect pane patch panel interface communications connection between two types of machines. Interface may be parallel, where each communications bit has its own wire and an additional wire known as a strobe line indicates to the receiver when data should be read. Parallel interfaces are us interference 1 optic 2 electromagnetic Interlock A mechanism for temporarily interconnecting several dimmer handles together. An electrical safety device that removes power from equipment when access covers are opened. interlock mechanical interlock Internal Reflector A focusing reflector (usually parabolic or elliptic) within a lamp. Proximity Reflector Inverse Square Law An equation relating the intensity of the source to the illumination it produces at a given distance. Iris A device from which a circle is cut out, inserted into a special slot in non-variable lens profile spots or follow spots in order to reduce the size of the beam. An arrangement of thin plates that form an opaque area with a circular opening in the center. Iris Diaphragm iris down to close the iris thus making the beam smaller iris out using an iris to make a beam smaller and smaller until it is no longer visible. Used as an effect in performance to gradually concentrate light on a singer?s face. Irving, Henry 19th century actor-manager Isora Plastic skycloth lit from the rear Izenour, George C. American pioneer of lighting control and theater consultant. Jones connector Connector used for console-dimmer communications in analog systems. joystick Protruding lever on control boards (and other computer systems) generally used on lighting boards for movement control of computerized luminaires. juice slang for electric current or voltage jumper extension cable K wheel flicker wheel Kelvin scale SI (scientific) unit of temperature. 0 degrees K = about -273 degrees C (the degrees are the same size in both scales). Used in theater lighting to define color temperature. Key-Light The principal source of light which establishes the character of the actor together with the atmosphere and mood of the scene keyboard in computer systems a board with alpha-numeric buttons used to type verbal instructions. keystone In lighting: the distortion of a projected image when it hits a projection surface at an angle other than 90 degrees. In stage technology: a 1/4'' piece of plywood used to connect toggle bar and stile on a flat. Keystoning The shape distortion of a projected image that occurs when a projector is not directed perpendicular to screen. kicker 1. side backlight from a low angle, or any source used to provide highlights. 2. A side or back light often near lens height, used to rim faces and model profile shots. An instrument used to provide an additional highlight or accent on a subject kill switch off a circuit. To turn off a light(s). kilowatt unit of power (1000 watts) Key Light A primary or main source of front light. Kelvin Kelvin, William Thomson, 1824?1907, British mathematician and physicist. Kelvin calculated that molecular motion stops at -273.16 deg C. Kelvin's model describes the change in color of light emitted by a black body. At this temperature there is no moveme temperature temperature the measure of the relative warmth or coolness of an object. The size of the degree depends on the particular temperature scale being used. The most common reference temperatures are the MELTING POINT of ice and the BOILING POINT of water. L.I.F designations are generic designations applied in certain classes of lamps and are standardized by the Lighting industries Federation, an independent specialist trade association in the UK. They are analogous to A.N.S.I designations but often do not distinguish between ladder side-lighting position shaped like a ladder and installed in the wings above head height. Used for hanging lamps, not for climbing. lag fade Crossfade where previous lighting state dims out more slowly than new state dims up. Lambert (L) Former unit of brightness. The luminance of a uniform light diffuser (a surface) which radiates or reflects one lumen per square cm. 1 lambert = 3180 candela per sq. meter. lamp check pre-performance check to make sure all units are working and focussed Lamp Dip A colored transparent or translucent lacquer used on low-wattage incandescent lamps in those instances when it is not possible to place color media in front of the equipment. This cannot be used on tungsten-halogen lamps due to the high bulb wall temperat lamp envelope transparent envelope enclosing the light source, made of glass in ordinary incandescent lamps and of quartz in the hotter tungsten-halogen type. lamp lacquer colored varnish in which lamps were dipped (see lamp dip) lamp life see Rated Lamp Life lamp lumen depreciation lamp singing SCR dimmers produce steep wavefronts which may pulse lamp filament and supports and produce an audible singing noise. This is particularly disturbing in television and may be remedied by using a large choke with the dimmer. lamp Light source. Refers to the complete unit including filament or electrodes, glass envelope (bulb), and other components. In the theatre it is sometimes used to refer to a lighting instrument, which can be confusing. lantern lighting instrument, luminaire laser light amplifier used to produce monochromatic coherent light. Used in theatre to create visible patterns. Patterns may include undulating waves, tunnels and other apparently three-dimensional shapes when projected through smoke, or graphic images when pro Laterna Magika Czech performance group founded by Josef Swoboda which uses film projection in conjunction with live performance. latest-takes-precedence control board principle causing the latest command to be effective although other commands to the same circuit are present on the board. As opposed to ?highest takes precedence? which is preferred for dimmer control, LTP is useful for mechanical devices s Layout 1. A ground plan of the scenery, stage and hanging positions. In repertory theatre this will also include the instruments in the permanent rig. 2. A scale ground plan of the scenery, stage and hanging positions. The lighting plot is based on the Layout an Lighting Plot, Lighting positions, Scale Plans, Preparing Plans Legend LCL (light centre length) Distance between the center of the filament of an incandescent lamp, and a standard point on its base. LD (lighting designer) Person responsible for lighting design of a production. This includes planning the type, position, color and focus of lighting instruments, ensuring the implementation of the plan, and determining intensity and changes in the lighting (cues) in cooperatio LDE: In television, a lighting director engineer, See Lighting Designer. Left Stage To the actor?s left as he faces the audience. Legend A table appearing on any light plot, ground plan, cross section or layout, denoting the graphic symbols used to indicate the various instruments and other elements appearing in the various plans, as well as indicating the name of the show, director, theat Legs Narrow flats or fabric drops placed at the sides of the stage in order to hide the backstage and wings from the audience and to limit sightlines. Legs are often black, but can be of any other neutral color or painted and designed to merge with the scenery Leko Lekolight Lekolight American ellipsoidal reflector spotlight, named for its inventors, Levy and Kook. Often used as a generic term for any ellipsoidal reflector spotlight. Lens Aperture f-Number Lens Projector In theatre lighting, a high wattage scenic slide projector, usually of wide angle coverage and sometimes with a moor drive to move a film strip. Lens Size For theatrical luminaires, the specification of diameter and focal length, e.g., a 6?x9? PC would be a 6? diameter, 9? focal length plano-convex lens. lens speed f number Lens Spotlight A luminaire embodying a lamp and a simple lens (plano-convex or bi-convex), with or without a reflector, which has variable field and beam angles obtained by changing the spacing between the lamp and lens. lens Glass shaped to bend (refract) light rays which pass through it. (see also: PC, fresnel, step lens, objective lens, condenser lens) level intensity of lighting circuit lever handle on lighting control board used for level control Life See Rated Life and Service Life life performance curve Graph of the change in output of a lamp throughout its life Light Light, that part of electromagntic radiation to which the human eye is sensitive. The wavelengths of visible light range from 380 to 760 nm. If white light, which contains all wavelengths, is separated into a spectrum, each wavelength is seen to correspon light absorption All substances absorb, reflect and transmit light in different proportions. Black velvet absorbs the major part of light that strikes it and is useful for ?infinite? backdrops. Color filters transmit light of certain wavelengths and absorb the rest, conve light batten lighting batten light box A shallow box with lamps in it, with one closed face generally painted white, and one face which may be open, covered with diffusing material, or perhaps cut in the shape of moon, sun or any other desired shape. This is then fixed to the back of a cloth o light bridge lighting bridge Light Center Length (LCL) The distance between the center of an incandescent lamp filament and an arbitrary, but standard, point of the lamp base. Light Change A transition from one lighting state to another. A light change can be a crossfade, a split crossfade, an auto follow, a cut, a fade in or fade out. Light changes are noted in the cue sheets, using a standard set of symbols cue sheet light conversion filter A filter which absorbs certain wavelengths and allows others to pass through, generally used in film and TV lighting to adjust color temperature of a light source, or in theater to achieve the desired tint of white light. Light Cue Cue light curtain Batten of low voltage lamps, usually 8 to 10 wired in series, to create a narrow strip of intense light. When several of these are hung in a row a ?wall? of light is visible onstage, particularly when the air is filled with smoke or haze. light distribution intensity distribution light distribution graph intensity distribution graph light fall-off illuminated area just outside the field, that is, just outside that part of a light beam where the intensity is at least 10% of the maximum. light flux luminous flux light Intensity luminous intensity light leak unwanted light that escapes from a spotlight, often through ventilation holes, or from between joins of scenic material. Light Lift A pantagraph or other adjustable-height device used to support luminaires from the grid. light meter apparatus used to measure various aspects of light such as intensity or color temperature Light Plot The complete layout of lighting equipment and its application in a production. light scatter light of low intensity cast by a spotlight outside of its main beam. indirect light light source In theater generally an incandescent or discharge lamp. lighting angle Angle at which light strikes the actor?s head, drawn between the lamp and a horizontal line at head height parallel to the stage floor. Lighting Area An area defined by the light from an instrument or a group of instruments. lighting balance Respective intensities of several circuits, so that it is clear which is dominant. lighting batten A pipe and wireway assembly suspended by wire cables with pigtails or receptacles which serves both to physically support the luminaires and to provide electrical power. lighting board #NAME? lighting booth #NAME? lighting bridge Lighting position above the stage or auditorium where luminaires can be mounted and on which people (electricians) can walk or crawl. lighting console #NAME? lighting control Regulation of circuit intensity and of the timing of lighting changes. Modern computerized boards enable control of other devices and aspects of lighting such as color, moving lights etc. lighting control board Board which enables operator to send control signals to dimmers and other controllable devices. This may be manual, in which case control is usually achieved by a set of levers to determine circuit intensity, or computerized, in which case the board can lighting control booth That part of the theater where the lighting control board is located, usually at the rear of the audience to afford a full view of the stage. lighting control console lighting control board lighting control desk lighting control board lighting control room lighting control booth lighting desk lighting control board lighting director Responsible for the execution of lighting for a performance. May also be the lighting designer. lighting effects catch-all term for lighting which may also refer to special effects such as flame, cloud projection, etc. Lighting Elements A list which expresses the artistic organization of the lighting. Can be textual, graphic (using in thumb sketches or using miniature floor plans or a combination of both) and indicate the groups of instruments which the lighting designer intends using, Lighting Equipment All equipment necessary for rigging, hook-up and operation of the lighting, including: trusses, instruments, clamps, tools, accessories, color filters, cables, electrical connections, dimmers, control board, and so on. Lighting Grid: A fixed structure of either aluminum or steel members, such as pipe, which is located above the studio floor for the purpose of supporting luminaires and to support the electrical outlets required. lighting manager (British) In charge of lighting in repertory theaters, of supervising changeovers and preserving lighting designed by designers from outside. lighting operator board operator Lighting Plans A set of technical plans and lists prepared by the lighting designer, and in accordance with which the rigging and focusing will be done. These include: the lighting plot, cross sections, hook-up plan, hook-up list, equipment list and color list. The ligh Scale Plans, preparing lighting plans Lighting Plot A scale drawing (usually 1:20, 1:25 or 1:50) indicating the exact location and direction of each instrument in relation to the stage, scenery and hanging positions (based on information from the Ground Plan and from the Layout). The Lighting Plot will als Legend, Cross Sections, Focusing, lighting pole Lighting Positions Hanging Positions, Rig lighting rehearsal lighting rig 1) Structure for hanging and supporting luminaires and other production equipment, consisting of structural elements such as trusses, ladders, pipes etc. as well as motors, chains and related hardware 2) Complete set of luminaires used in a production, lighting score Outline of proposed changes and development of lighting throughout the show lighting software Most available software consists of lighting plot drafting programs which also generate related paperwork, and often include comprehensive equipment libraries. New programs are being developed as design aids, with varying degrees of visualization, and com Lighting State A static state of the lighting determined by the specific instruments which are lit and the intensities. The transition from one lighting state to the next is known as a cue. lighting tower Tall stand or platform on which luminaires may be hung. Lighting Transitions The manner in which one lighting state is changed to another lighting state in the course of the show. This can be a fade in, fade out, cut, cross fade, blackout or follow-on. lighting truss Sturdy aluminum support structure, consisting of sections bolted together in various configurations, which may be hung from the roof or supported from the ground. Used primarily in situations where standard lighting positions do not exist, e.g. outside pe lighting unit Any device used in a lighting plan, e.g. luminaire, strobe fixture, etc. lightning High-intensity luminous electrical discharge between earth and cloud, or between two clouds. May be reproduced in theater lighting by photoflood lamps, by lightning-shaped gobos placed in intense luminaires and pulsed quickly, strobe lights, and other mea Limbo A background having no detectable detail; for theatre and television, black; for film, white. lime box (British) Room at the rear of the auditorium intended for follow spots (originally limelight). Usually behind highest balcony. limelight First directional theater light source. The flame from a mixture of oxygen and hydrogen heated a block of limestone, which then emitted intense light of a soft white color. Used from front of house as a follow spot. limes (British) Slang for follow spots and follow spot operators. linear flood Floodlight using linear double-ended tungsten-halogen lamp Linnebach A lensless projector formed by a box painted black on the inside and containing a ?point? source of light such as an incandescent lamp with a small filament. A cutout or a transparency (often painted on glass) is placed on the open side of the box. The L liquid dimmer Early version of resistance dimmer where liquid was used instead of resistance wire. It consisted of a container filled with water and an electrolyte as an aid to conduction, such as salt or dilute sulphuric acid. At the bottom was a fixed electrode, and llght source efficiency Light output of a lamp in relation to its power consumption, expressed in lumens per watt. load electric load load sensitive dimmer Dimmer such as the resistance dimmer which must be connected to the appropriate load in order to achieve a smooth dim. When a smaller load needed to be dimmed additional ?ghost loads? were often connected offstage. load-in Unloading a production into the theater. (Get-in in Great Britain) load-out Taking down a production and loading it onto transport for removal from the theater. (Get-out in Great Britain). Loader Usually a plano-convex spotlight with lens removed used as a phantom load. lobsterscope Perforated wheel rotated in front of a luminaire for a ripple effect. KK wheel loop 1)In computer control boards, a set of cues which repeat themselves. 2)In general control systems, a closed-loop system involves feedback which influences the controlling device. Loutherbourg, Philip James de Louvers (also spill shield): Thin parallel or cylindrical strips located in front of a reflector to reduce spill or direct light that falls outside of the main beam, usually of black finish. Low Key Lighting A type of lighting which, applied to a scene, is intended to produce a picture having gradations from middle gray to black with comparatively limited areas of light grays and white. Low Noise Lamps Incandescent lamps having special construction to minimize the generation of audio noise when operated on ac circuits and especially on dimmers which distort the sine wave. Low Sidelight Light from a low angle at the side. Often used in dance to emphasize movement of the dancers? bodies. Sidelight low-key lighting High-contrast lighting with large areas of darkness and shadows. low-pressure mercury lamp Discharge lamp filled with mercury vapor at low pressure, which produces radiant energy within the ultraviolet part of the spectrum. The inside of the lamp is coated with a fluorescent coating or phosphor, which converts the UV radiation into visible lig LPS (low-pressure sodium) lamp Discharge lamp filled with sodium gas, used in road and architectural lighting. Has a characteristic nearly monochromatic yellow color, nearly all in the wavelengths of 589 and 589.6 nm. Lumen SI (scientific standard) unit of luminous flux equal to the flux emitted by a luminous point source of 1 candela in a solid angle of 1 steradian. Lumen Per Square Foot A unit of illumination. 1 im/ft2 = 1 fc. Lumens Per Watt (LPW) The number of lumens produced by a light source for each watt of electrical power supplied to the light source. Also see Efficacy.e.g. if a 1000 watt lamp produces 20,000 lumens , then its efficacy is 20 LPW. Luminaire A complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps, and to connect the lamps to the power supply. luminance ratio brightness ratio Luminance A measure of the light (flux) per unit area leaving a surface in a particular direction. The unit is the footlambert. This quantity was formerly known as ?brightness?. luminescence Emission of light by a substance for any reason other than a rise in its temperature (incandescence), for example bombardment by electrons. If luminescence persists after the cause is removed it is called phosphorescence; if not it is called fluorescence. luminous efficacy The efficiency of a light source, that is light output in relation to power consumption, expressed in lumens per watt. luminous flux Amount of light passing through a specified area in one second. Derived from radiant flux (radiated power expressed in watts) and measured by reference to emission from a standard source, usually in lumens. luminous intensity Amount of light emitted per second in unit solid angle by a point source, in a given direction. Measured in candelas. Luminous An adjective to indicate the production of light., e/g/ ? luminous source? to distinguish from electrical sources, etc. It is sometimes used before ? intensity? or ?flux?. Lux The unit of illumination used predominately in Europe; equal to one lumen distributed uniformly over one square meter LV (low voltage) Most low voltage luminaires used in theater lighting are sealed beam (PAR) lamps which emit a narrow concentrated beam. Common lamps are 6V, 12V, 24V, 28V, and are used with a transformer or wired in series. The lighting transitions are indicated in the MR16, ACL macro key A programmable ?soft key? on many computer lighting boards which can be programmed with any desired function or set of commands. magazine batten Floodlights in three or four compartments, usually each in a different color for color wash of stage or cyc. battens. border lights magic lantern early optical projector using a transparent slide. Magic Sheet A condensed reference sheet indicating the function (can also include direction, color, position etc.) and control channels of the lighting elements. Magnetic Amplifier A development of the saturable reactor dimmer in which a low-voltage DC control circuit changes the magnetic properties of the inductor core. One of the first remote-controlled dimmers, it was popular in the 1950?s as an alternative to the thyratron tube Lighting Plot magnetic clutch Electro-magnet which when energized by a control current from the lighting control board caused a mechanical dimmer to be moved by attaching the dimmer arm to a drive shaft. main light key-light main switch Switch at the point where mains electricity is supplied to the stage; in nearly all installations this is a three-phase system. The main switch is generally equipped with fuses or circuit breakers, one for each phase though circuit breakers may be interco manual control Lighting control by human fingers, usually adjusting levers on a control board Manual Dimmer A dimmer which has only mechanical linkages between the control lever of the unit and the moving electrical contact which conducts the electrical power supplied to the luminaire load. maroon Electrically fired pyrotechnic effect which sounds like an exploding bomb. Martingale Twofer mask 1) Lighting: To conceal a lighting instrument from the audience ; to cut off part of a beam of light. 2) Stagecraft: to hide part of the stage area, usually wings and flies master Switch or dimmer used to control other switches or dimmers for individual circuits. A grand master controls all switches or dimmers while a group master controls only a group of switches or dimmer. master electrician chief electrician master fader master master/slave Certain lighting boards may be linked to other boards in a master/slave configuration so that one board controls the other with its master faders, blackout buttons, etc. but the other board may be used as an additional control unit. Mat(or Matte) When used to describe surface, this means dull or diffuse as opposed to mirror-like; a diffuse reflecting surface; one that reflects light uniformly in all direction; a ?flat? surface in the sense of flat paint. This term also is used to imply ?soft ligh Maximum overall Length (MOL) The maximum dimension of a lamp from base to base for double ended lamps or base to extreme point of bulb for single ended lamps. McCandless Method A method of lighting the stage by dividing it into acting areas and illuminating each acting area from two frontal angles of 45 degrees vertical and horizontal, thus providing even and controllable illumination of the entire stage. McCandless recommended McCandless, Stanley American lighting designer, teacher and theorist whose ideas, published in ?A Method of Lighting the Stage? (1932) had vast influence and were probably the first methodical treatment of design in theater lighting. He taught at Yale University and his most mechanical dimmer Dimmer which gradually fades light up or down by obstructing it rather than by influencing the light source. These are usually in the form of Venetian blinds controlled by a lever, either manually as in many follow spots, or electronically. Some computeri mechanical dimming shutters Shutters which dim the light by obstructing it. Meiningen company Acting ensemble directed by the Duke of Saxe-Meiningen, which toured Europe from 1874 to 1890 and was vastly influential. Their work was characterized by meticulously accurate sets,, costumes and properties, long rehearsal period, and crefully planned ex Memory A device for storage of intensity and other information for combinations of luminaires (cues or presets) for use during the course of production. Originally accomplished by potentiometer arrays (presets), now usually volatile or nonvolatile electronic el memory board Memory mercury-vapour lamp High intensity discharge (HID) lamp which emits a bluish-whilte light with no red radiation, though some lamps have a phosphor coating on the bulb interior which adds some red. metal-halide lamp Discharge lamp containing mercury vapor as well as some metallic iodide vapors (such as indium, thallium, sodium, scandium) under high pressure, which improve the color distribution of the lamp. Light is greenish white though phosphors may be added to the Midget Inky MIDI #VALUE! Midi time code Method of sending SMPTE (q.v.) time code over a MIDI line. MTC breaks SMPTE TC messages, which are analog, into MIDI messages which may be transmitted digitally through a MIDI line. milliphot One thousandth of a phot (q.v.) mimic display Visual display, generally on a monitor, of channel levels and other relevant information. mirror ball An approximately spherical ball whose surface is covered with small plane mirrors. When a spotlight is shined on the ball and it is rotated, multiple moving spots of light sweep across surrounding surfaces. mirror scrim Gauze which is transparent when objects behind it are lit, and with no light behind behaves like a mirror mirror spot Early British profile spot manufactured by Strand Electric Mise-en-scene The movement of the actors from one part of the stage to another and their actions in the course of the show as determined by the director during rehearsals. The mise-en-scene is noted verbally or graphically on miniature ground plans of the set. Also ref mist A light haze which may be produced by certain smoke machines, or by stretching a gauze before the misty area. Modelling-Light That illumination which reveals the depth, shape and texture of a subject. mogul base Large screw lamp base used on large wattage lamps (known as GES in Great Britain) MOL Maximum Overall Length Monochrome The strict use of only one hue in various intensities or values, in scenery, costume or lighting. monochrome scenery monoplane Type of filament common in incandescent non-halogen theater lamps where the filament is arranged in a plane parallel to lens and reflector to emit the maximum amount of light in their direction. monopole Luminaire suspension device consisting of seven or eight telescopic interlocking steel tubes from which a luminaire is mounted, and can be raised or lowered by a wire rope winding system. They may be manual or motorized and have a safe working load of 45 Montage Erection of the scenery on the stage. moon box Box with one face cut out in the shape of a moon, with lamp or lamps inside it. This may be placed behind a sky drop to shine through it, and may also be moved slowly to travel across the sky. MOSFET (metal-oxide silicon field-effect transistor) semiconductor dimming device which uses reverse phase control; that is, it turns off the waveform at a specific point rather than turning it on as does the SCR. The absence of a sharp turn-on spike eliminates SCR, IGBT motivated light Light which is ostensibly caused by a specific source such as lamp, window etc. motivation light Motivation Light An actual light source on stage or the presumption of such a source which will give the lighting state its key. Usually used in realistic lighting. For instance, in daytime the motivation light can come through a window. In a interior night scene light th motorized light moving light moulded lens Fresnel lenses may be moulded rather than ground and polished: Separate concentric rings are moulded and then pressed in a larger mould. Therefore they can be manufactured in larger sizes than PC lenses and are less expensive. mouse 1) Hand held device which allows interaction with a computer system: moving it causes a corresponding indicator to move on the computer screen and buttons on the device may be pressed to initiate commands and generally interact with the system. Some ADB c moving effects effect machine moving light Two basic types of moving lights exist. The first consists of a moving luminaire with motors which control pan and tilt of the entire luminaire, and usually additional motors to control beam spread, size, and color. The second type is a static luminaire w MR-16 Small sized luminaire consisting of a tungsten-halogen lamp and dichroic reflector 50mm in diameter. (MR-16 actually refers to the reflector; smaller reflectors are the MR11 and MR13). Used as an alternative to PAR 38 and other incandescent reflector lamp MSC (Midi show control) Standardized communications protocol for interconnection between different types of control systems. Each controller uses its own controller-to-device protocol: for instance a lighting board would send DMX commands to dimmers but receive and/or transmit c MSR (Medium Source Rare earth lamps) discharge lamps available in wattages from 400 to 2500W, which produce a continuous spectrum of relatively white light with about 5600K color temperature. Multi-Media The use of two or more projectors of different types, e.g., motion pictures and slides, in a multi-image presentation. multicable multicore cable multicore cable Cable which contains many wires to allow connection of several different circuits and generally terminates in multi-pin connectors. Six-circuit 18-strand multicore cable is common and used with six-way lighting bars, but many other variations exist. multiple pages Function on computer control boards with manual facilities which allows the same faders to control different lighting states depending which 'page' is selected. multiplex Method of sending multiple information over a single channel. Lighting control generally uses time-multiplexing; each channel is split into time slices which are sent one after another, and reassembled at the end of the line by a demultiplexing or 'demux' Multiplexor In television, the optical system used to route multiple projected film images into the film chain camera. multipurpose luminaire Luminaire developed for television in 1961 consisting of a softlight back to back with a Fresnel ('hard light'). Munsell Albert Munsell, In 1905 (1915?) published a book 'Color Notation' in which he detailed a color system and thus created an international common language and standard to define color of pigments. Munsell system System of color definition consisting of three attributes: 1) Hue - what basic color it is: red, blue etc. 2) Brightness - how bright or dark the color appears, actually a function of the amount of light reflected 3) Saturation - how pure the color is; ho music-stand lights Orchestra musicians in musical productions need to read music untroubled by onstage lighting changes; for this reason music stands are installed with small localized light sources, often low-voltage. mylar filters Plastic color medium with high transmission factor and long life. Not many colors are available, and the material is expensive, but useful in situations where long life is important. nanometer(nm) one billionth of a meter (10-9 meters) Natural Light The way in which light falls in real life situations such as a bright sunlit day, a sunrise, a dimly lit room and so on. Copying the actual intensities and sources of natural light onto the stage will not be effective, but the lighting designer can use na ND (neutral density) filter Filter which reduces light intensity without affecting its color. neon lamp Discharge lamp filled with neon gas which produces vividly colored light. The color may be changed by using mercury vapor and fluorescent coatings. Neon has been used since the 1920's for advertising displays. neutral The common grounded connection in an alternating current three-phase system. In household (and theater) sockets and wiring the neutral is that terminal or wire which is at zero potential with respect to earth. Newton Newton, Sir Isaac, 1642?1727, English mathematician and natural philosopher (physicist); considered by many the greatest scientist of all time. He discovered that white light is composed of every color in the SPECTRUM. Newton's theory that LIGHT is compos Newton?s Disc Another way of showing that red, orange, yellow, green, blue, indigo and violet combine to give white light involves spinning Newton?s Disc. A disc with color sector painting on it is rotated. As the speed of rotation increases the disc look white (if you Nedervolt German for low voltage, and used to refer to low voltage lamps such as AC battens, 12V PAR lamps, etc. Nit unit of luminance equal to one candela per square meter. non-dim circuit A circuit supplying electrical power to a luminaire by means of a switch or a relay in order to permit an on-off function rather than a dimming function. non-lens spotlight A luminaire embodying only a lamp and a reflector which has variable field and beam angles obtained by changing the spacing between the lamp and the reflector. nonspectral hue A hue not present in the natural spectrum, but achieved by additive mixing of other colors. Magenta is a nonspectral hue produced by additive mixing of primary red and primary blue. object color Pigment molecules in the surface of an object capture some wavelengths of light and cause others to rebound into space. When these reflected wavelengths enter the eyes they are experienced as the color of the object. When the light falling on an object do obective Lens Projection Lens off-line editing Some lighting computers allow cues to be built 'off-line' on PC computers, recorded on disc and then loaded into the lighting board. This may be done outside of the theater, during the planning stage for instance, and saves valuable plotting time which ma offstage out of sight of the audience; away from the center of the stage. ohm SI unit of electrical resistance, defined as the resistance between two points on a conductor when a constant potential difference of one volt applied between the two points produces a current of one ampere in the conductor. Ohm's law V=IR, (where V=potential difference in volts, I=current in amperes and R=resistance in ohms). I n words: the ratio of the potential difference between the ends of a conductor to the current flowing through it is constant and this constant is the resista oil lamp Vessel containing oil and one or more wicks. Used from earliest antiquity thousands of years BC. The light produced was white but its color as well as the amount of smoke emitted depended on the quality of the oil and the wicks. Argand lamp Olivette An early type of floodlight with a box shaped enclosure and a diffuse painted reflecting surface. One-K Ace onstage in sight of the audience; toward the center of the stage . opaque Does not transmit light. Opaque Projector A device that will project an image of opaque material such as a printed page. open faced luminaire A luminaire without a lens, containing light source and reflector. Open White Indication that a luminaire has no color filter. Usually noted as O.W. in lighting plots or various lists. Also noted as CL (clear) or NC (no color). optical axis Imaginary line passing through the optical center and the center of curvature of a lens or a spherical mirror. In luminaires efficient light output depends on correct positioning of the lamp and other elements with respect to the optical axis. optical density Refractive index of a medium; the extent to which light changes direction on entering it. refractive index optical fibres Glass fibres which conduct light. Step-index fibre consists of a glass core surrounded by a glass or plastic cladding of lower refractive index. This causes total internal reflection of light within the core as the interface of core and cladding acts as a optical illusion Any distorted or incorrect perception. Optical Shift The dichroic filter has optical characteristic known as optical shift. A blue filter will transmit blue light, on condition that the light is perpendicular. If the filter is tilted 30 degrees with respect to the light beam, the filter will shift the wavel optical system any system including optical components such as lens, reflector, etc. orchestra pit Area in front of the stage for musicians, usually lower than the stage and often extending underneath it. out of focus Projecting an image whose edges are not clearly defined. This is usually a result of lens position. overhanging Hanging a spotlight above a lighting bar rather than suspended from below it. overhead light toplight Overhead Projector A device which projects the image of a horizontal transparency onto a vertical screen. The transparency may be a copy of printed material, illustrations, etc. or it may be a copy of printed material, illustrations, etc. or it may be writing done with a s Overlap Merging of two or more beams of light into one another to create an even wash. overload Plugging into a circuit more lamps than that circuit is able to carry, which will generally blow a fuse. Package Dimmer Modular units containing several dimming circuits; units can be arranged in various numbers and combinations. Paddle Stage Plug Pageant 1K beamlight introduced in the U.K. by Strand Electric, which produced an intense parallel beam of light. Originally used in 1935 for a pageant in the moat of the Tower of London. pairing Connecting two or more lights to the same circuit. Also called twofering. pan Sideways movement, used when dealing with moving lights, along with tilt (up-and-down movement) panorama 18th and 19th century exhibition entertainment also used as scenery, consisting of a large scenic painting either static or moved on rollers from one side to the other. pantograph Mechanical scissor-like apparatus for varying luminaire height. May be spring balanced, motor operated, or use a manually driven gear system. Pantographs are used in television studios, mounted on trackways which allow their easy movement. PAR lamp (Parabolic Anodyzed Reflector) Sealed beam lamp consisting of filament, reflector, and glass envelope. The glass may be clear, diffuse or patterned, which affects beam spread. The lamp produces a directional 'punch' of light with indefinite edges and a co Par Light A spotlight-like luminaire using a PAR lamp. The beam characteristics depend upon the PAR lamp used. parabolic reflector Reflector in the shape of a parabola. Light emitted from a lamp at the focus of the parabola will be reflected in parallel rays. Used in searchlights, beamlights and most sealed beam lamps. Parabolic Spotlight Beam Projector Parallel Bed Parallel Circuit A parallel circuit is characterized by all the loads working at the same voltage as the source and independently of one another. That is, if one load is switched off, the remainder are unaffected. If another load is added in a parallel system, it supplies parcan Another term for Par lamp (q.v.) patch To make connections on the patch panel. patch bay patch panel patch panel System for cross-connecting circuits to dimmers. This may be a plug-and jack-system, or a system of busbars interconnected by handles or pins. Older patch panels used rotary dials but these were only suitable for very small installations and are more or l soft patch, control patch pattern gobo Pattern Spotlight An ellipsoidal reflector spotlight, especially one with a pattern or 'gobo' slot at the focal point of the unit to permit insertion of pattern templates for projection. PC lens Plano-convex converging lens used in spotlights to concentrate the light, and characterized by diameter and focal length (in inches). A 6x9 lens has a 6' diameter and 9' focal length. The diameter influences light intensity as a larger lens can collect mo PC spot Focus spotlight with PC lens, spherical reflector and light source. Beam spread is adjusted by bringing reflector and lamp closer or farther from the lens. PCB (printed circuit board) Plastic board with electronic components and wiring on it. These are found in dimmers and translate the control signal to dimmer operation. One common reason for analog dimmers not to work is the PCB has been dislodged from its place. In more sophisticate peak light distribution That part of a light beam where difference in intensity is not more than 1:2. pebble-convex lens (PC) Plano convex lens where the convex surface has been stippled to provide a softer beam edge. Also called prism convex. Pedestal Refers to the black level in picture information in television; established gray scale. Pepper's ghost 19th century lighting effect where an actor is hidden in the orchestra pit while his image is projected onto an invisible sheet of glass onstage making him suddenly appear and seem transparent. Named for John Henry Pepper who presented it at the Royal Pol perch Lighting position at the side of the stage behind the proscenium, above head height. Performance A play or show performed for an audience. Period (of play) The epoch, era or age at which the play or staging of the play takes place. tis can be Classical Greece, Renaissance, 19th century, contemporary or any other period.The period of a play is evident in the scenery, costumes and props, including various prac Peripheral Equipment 1) Equipment used to enhance the lighting such as smoke or mist machines, lightning generators, effect machines, projectors and pyrotechnics. 2) Equipment used to assist in the rigging, such as trusses, clamps and stands. 3) Instrument accessories. 4) Co Phantom Load An 'off-stage' load applied to resistance type dimmers when the functioning load is less than the minimum rating of the dimmer. This is necessary since resistance dimmers will not dim effectively unless the total connected load meets the dimmer rating. phosphorescence Emission of light of one wavelength by a substance which has absorbed electromagnetic radiation of a shorter wavelength. May continue after the incident radiation has ceased. luminescence, fluourescence phot (ph) Unit of illuminance equal to one lumen per square centimeter. photoflash lamp Electrically operated flash lamp. photoflood lamp Lamp which uses excess voltage to produce intense light, used for photography. photometer Instrument for measuring various attributes of light such as intensity and brightness. Photometric Data Data relating to the light output of any given instrument. This includes: type of beam, field, spot and flood intensities, throw, bulb types, wattage. Photometric data can be shown in graphs or in tables and often appears in catalogues or advertising mate photometry Science of measurement of light photopic vision polar vision photoreceptors Sensory cells that react to the presence of light, usually containing a pigment that reacts with a chemical change when light is absorbed, which stimulates a nerve. Piano Board Originally, a portable resistance dimmer switchboard in an upright castered wooden box and used as a Road Board. Now the term is sometimes used for other types of portable dimmer switchboards. Piano Box Pictorial Lighting A style where realism is accentuated or heightened. Pictorial lighting is based on the same organizational principles as realistic lighting, but it heightens certain selected elements. Colors and hues are somewhat exaggerated in relation to their counterp Pigments Powdered coloring material used to give hues to paints and ink. Pigtail The short cord with connector coming from a device such as a lighting instrument or a wireway. Pilbrow, Richard Influential British lighting designer and theater consultant, author of Stage Lighting. Pile-on To override a preset with another higher preset. pile-on cue A cue consisting of a preset added on to an existing preset. pilot light Also called work lights or running lights, these are dim lights often gelled or painted blue to provide light backstage during performance without illuminating the acting area. pin matrix Patch panel for control circuits consisting of busbars cross-connected by pins. They are used for control patch systems and also as emergency back up with computer systems to patch groups of light to faders. pin patch pin matrix Pin Plug or Connector Electrical connector using round cross section pins. pinspot Low voltage sealed beam luminaire which produces an extremely narrow beam. Pipe Batten Pipe Clamp A device that connects the yoke or pipe arm of a lighting instrument to a pipe batten or boomerang. pipe ends High side-lighting angle common in dance lighting where a wash is achieved by positioning luminaires at each end of the lighting pipes. Pipes A series of pipes hung over the stage parallel to the stage opening, at regular intervals. The pipes are used to hang scenic elements or lighting equipment. Pipes on which lighting equipment is hung are referred to as elex bars or pipes. The pipes can be PL lamp Low wattage energy-efficient compact fluorescent lamp. Plano-Convex lens PC lens Plano-Convex Spotlight Focus luminaire with a plano-convex or pebble convex lens, spherical reflector and lamp. Beam size is adjusted by moving lamp and reflector with respect to lens. The beam has clearly defined edges. P.C. Spot plaster cyclorama Permanent semi-circular plaster surfaced background at the rear of the acting area and lit to represent the sky and give a feeling of infinite space. Common at one time in European theaters. plastic filters Plastic color filters may be thin, such as vinyl or mylar, or heavy such as acetate or polyester. Plasticity The qualities of light and material which enable an object or figure to appear fully three dimensional and sculpted. Plate A single resistance dimmer unit Now, by analogy, applied to other types. playback That part of a computer lighting board which causes prerecorded cues to be operated. Playwright A person who writes plays or adapts other written material for the stage. Plot The light plot. Plotting The first session after focusing, during which the lighting states, intensities, transitions, changes and cues are determined, recorded and noted in the show manager?s text. Present at this session: director, lighting designer, scenic designer, costume de plug-in dimmer Modern dimmers are often manufactured in modules which may be plugged in to a rack. This facilitates replacement in case of dimmer breakdown. Plugging Box: A portable box with one electrical feed and outlets for two or more branch circuits; often contains branch fuses. Pocket individual or groups of outlets for stage circuits, often located under a protective trapdoor; e.g. floor pockets , wall pockets, fly pockets, etc. point light source A light source concentrated in a small area.Light sources in optical instruments should be as close to a point size as possible to obtain precise results and maximum efficiency. point source point light source polar distribution diagram Diagram used by manufacturers to display the intensity distribution of a luminaire. pole operation Television studio luminaires may be equipped with hook or hole attachments which allow them to be angled and focussed with a pole by a technician standing below. polycarbonate filters Plastic color filters, capable of withstanding high temperatures and more long-lasting then polyester as well as more expensive. polyecran Multi-screen background on which different images are projected at one time. Used by Swoboda with the Laterna Magika. polyester filters Plastic color filters capable of withstanding very high temperatures. pool of light Lit area with defined borders, generally from directly overhead. Dance lighting layouts commonly use a set of pools which together cover the entire dance area. pot potentiometer potentiometer Variable resistor used in control boards to control low signal voltages power assisted Equipment and luminaires directly controlled by an operator, for example winch control motor systems. power patching patch power rating electric power rating Practical A light source within the scenery, such as a chandelier, usually controlled through a dimmer. Can be used by the actor, e.g. a lamp that can be switched on and off by him. Pre-Production The period prior to rehearsals, during which the artistic team and casting are decided upon, technical and organizational data is compiled, schedules and budgets are determined, and initial decisions are made regarding the scenery, lighting and other elem prefocus lamp Lamp whose base ensures specific positioning. Bayonet prefocus lamps have two fins at the sides which lock into two slots in the socket. preheating Bringing up channels to a very low level so there is just enough current to warm up the filament without producing visible light. Premiere The first show performed in front of a paying audience (in certain cases a number of shows may precede the official premiere). The premiere is often a festive occasion to which various people connected to the production or theatre are invited as well as preset 1) A row of potentiometers on a manual lighting board used to control channel levels to produce a specific lighting picture. 2) A state of light onstage prior to audience entry or to curtain opening. Preset Control The control, usually a potentiometer located on the lighting control console, used to program or preset the output of a dimmer, and in turn, the light output of the luminaire connected to the dimmer. preset light A state of light onstage prior to audience entry or to curtain opening. primary colors Red, blue and green are the primary colors of light, that is, any other color may be produced by additively mixing them but they cannot be produced by additively mixing other colors. When mixed in equal proportions the three primary colors produce white l prism-convex lens (PC) A plano-convex lens with stippling on the convex side to soften the beam. Production Table One or more tables placed in the center of the auditorium for plotting sessions, lighting and technical rehearsals and run-throughs. At the production table, the lighting designer will need a lighting plot, magic sheet, cue sheets and access to the board Profile Spot profile spotlight Profile Spotlight Luminaire which enables precise shaping of the light beam and projection of a cut-out image. These are found in two basic types: 1) A luminaire with an ellipsoidal reflector, where all light from the lamp is reflected back to a second focal point. Shutte profiled cue Some computer control boards allow memorization of the specific timing of a lighting transition. For instance a transition might be slower at the first part of the fade and accelerate towards the end. Program To input information to a memory light board. Projected Scenery Scenery projected onto a background or other surface. projection Images on slide or film which are projected onto the stage, generally as scenic background or illustrative material. Projection Distance The distance between an instrument and the object/person being lit. projection lamp Incandescent lamp used in luminaires where the light is to be projected out in a specific direction. Also may refer to a lamp in a slide projector. These are usually tungsten-halogen low voltage lamps, though more powerful projectors use discharge lamps s Projection lens That lenses in projection system which images the slides, film, etc. onto the screen. It is the lens closest to the screen. projection room Room at the rear of the audience which may be used for projection projector Device for projecting an image, ranging from profile spot through the overhead projector, slide projector, film and video projector up to modern attempts at 3D projection. prompt corner Area behind the proscenium from which the stage manager runs the show. In the UK this is traditionally on the actors' left and stage left in fact is known as PS (prompt side) while stage right is OP (opposite prompt)! proportional dimming The fact that in an electronic dimming system all dimmers reach their end state of a transition at the same time. Older mechanical systems had non-proportional dimming where the end-state of each dimmer was a function of the distance its lever had to trav Props Any small moveable items or elements used by the actors in the course of a show. Short for Properties. For example: household objects such as cutlery and crockery, hand-held objects such as firearms cigars or fans, food used on-stage, books and so on. Proximity Reflector A small non-focusing reflector within a lamp and mounted immediately behind a planar filament. Internal Reflector psychedelic effects Moving color effects popular in the late sixties, particularly in discotheques and rock concerts. Usually produced by sandwiching colored fluids between two pieces of glass and projecting their movement to give a kaleidoscopic effect. pyrotechnics Firework effects such as smoke, flashes, bombs, usually electrically controlled. Q (*cue) Lighting transition or lighting state. Quality Sometimes used as a theatrical synonym for color. Quartz quartz lodine and quartz halogen Tungsten-Halogen quartz iodine lamp tungsten halogen lamp quartz lamp tungsten halogen lamp Quartz Lights Generic term for small lumiaires of various types (usually open reflector) that utilize tungsten-halogen lamps. quick flashing light strobe light R (reflector) lamp Usually referred to as ?R? These are low wattage flood units which combine the properties of reflector and light source into one unit. The most common lamp for many years was the R40 lamp. radiation The emission or transmission of energy in the form of waves through space or through a material medium; electromagnetic radiation may be viewed as made up of photons. Rail Light Balcony Spotlight rain effect Rain can be simulated by placing a painted glass rain effect disc in a moving effects machine. rainbow White light which has been broken up into a band of colors. rainlight A pinspot generally hung overhead with its beam aiming downward. rated lamp life Average lamp life as determined on a group of lamps under controlled laboratory conditions of constant applied voltage, etc. Service Life Ray tracing The application of the rules of geometrical optics to the study of optical instruments is known as ray tracing. The most elementary method of ray tracing is simple graphical construction. The more accurate methods employ mathematical calculations. Such Realistic Lighting A style of lighting which reflects reality and natural light as objectively as possible. The conceptual basis for realistic lighting is usually taken a motivation light. For instance, in daytime, the motivation light can be light coming through a window, Realistic Theatre, Styles in Lighting Realistic Theatre A realistic play presents a world which reflects reality as objectively as possible. Realistic Lighting rear projection Images projected from behind the projection surface. rear projection screen A surface suitable for rear projection. Special rear projection surfaces have a high transmission factor, a matt surface to avoid reflections from the front, and a diffuser to minimize the 'hot spot' where the projector is visible. record Computer control board command to memorize a lighting state or other information. redhead Open-faced flood luminaire used primarily in film and television. Its beam can be adjusted somewhat by moving the lamp with respect to reflector, and by use of barndoors. reference white equel energy spectrum reflction cloth bounce cloth reflectance (also reflection factor): A measure of how effectively a surface will reflect light, i.e. the ratio of the reflected lumens to the incident lumens on the surface. reflection reflection, return of light, from a surface it strikes into the medium through which it has traveled. reflection, (the law of) the law of reflection states that the angle of reflection (the angle between the reflected ray and the normal, or line perpendicular, to the surface at the point of reflection) is equal to the angle of incidence (the angle between the incident ray and the reflector a polished surface for reflecting light or other radiation. refraction a light ray bending in passing obliquely from one medium (as air) into another (as glass) in which its velocity is different. refractive index All materials that transmit light are characterized by a number called the refractive index, which expresses the velocity of light in that medium compared to the velocity of light in a vacuum. Rehearsal A session in which elements of the production are decided upon and practiced. Depending on the stage the production has reached, there are acting rehearsals, technical rehearsals, lighting rehearsals, run-throughs and dress rehearsals. Complex productions Reinhardt, Max Max Reinhardt, 1873-1943, was an Austrian stage director and producer who established himself as one of the most eclectic leaders of the modern experimental theater. Reinhardt was noted for his spectacular productions, which often involved unusual staging relay Eelectrically controlled switch that is used to open or close an electric circuit. A standard type of relay consists of a coil with an enclosed, fixed iron core and a nearby movable armature. When the coil is energized, the armature is attracted to it; th remote control Control of a device from a distance. This may be done by analog means, using a low voltage control current to influence the higher voltage current of the device, or by digital communication which transmits commands to a decoder at the device. analog, digital, protocol, multiplex, DMX RCD (radio controlled dimmer) Dimmer which receives control commands from a radio transmitter. These are wonderful when lights are to be placed on moving units, along with their dimmers, and were first used to great effect in Phantom of the Opera where moving boats held flickering can Remote Controlled Dimmer A dimmer which requires an electrical circuit or circuits a part or all of the transmission system between the central lever and the dimmer unit. Remote Pickup Television pickup outside of the studios. Repeat A lighting state which is repeated a number of times. Repertory Theatre A theatre which produces a number of plays every season. These plays, together with successful plays from previous seasons, are performed in rotation. Repertory theatres usually have a fixed rig of lighting which is refocused every evening depending on th resistance dimmer A variable resistance placed in series with a lighting load. retina the sensory membrane that lines the eye, is composed of several layers including one containing the rods and cones, and functions as the immediate instrument of vision by receiving the image formed by the lens and converting it into chemical and nervous s retrieve To recall information from a memory light board. Reverse Return to the previous lighting state. RFI Radio frequency Interfence - an electrical noise caused by radio waves of certain frequencies. rheostat A resistance dimmer. rhodopsin An organic compound formed in the rods of the retina of the eye, which makes the eye more sensitive in dim light. Lack of it causes night blindness. rhythmic light strobe light rig The array of hanging positions. In theatre the rig is usually permanent and consists of pipes (known as elex pipes), ladders, balconies, FOH positions and bridges. In smaller theatres where there is no stage tower and no pipes, there is normally a grid. rigger's control A lighting control unit smaller than the main board which can be hand held by someone on the stage and used to call up channels and cues during technical work. rigging The process of hanging the instruments on the rig in accordance with the lighting plot. In rock concerts or events held in locations where there is no permanent rig, this term also includes the trusses, stands and other positions on which the instruments rim light Back light which creates a halo or outline of light round an object or person, or a luminaire which is used for this purpose. Film and TV lighting term. ripple effect Moving effect created by passing a piece of metal with slits in it before a light source. Special ripple devices consist of a double-ended tungsten halogen lamp within a revolving metal tube with slits in it. animation discs, KK wheels rise time (Tr) ?Tr? defined as the time taken by the current to rise from 10% to 90% of its peak value when the dimmer?s firing angle is set at exactly the one half power point, that is 900 firing, with the inductor in the circut. The performance of an inductor may also Risers: The ridged surfaces on a stepped lens or a fresnel lens between sections of active lens surface, parallel to the optical axis. These are sometimes blackened to reduce stray light. Road Board A portable switchboard brought into a theatre for a show. also, see Piano Board. Road Plot A special lighting plot containing all elements and information pertaining to the lighting of a show, designed to indicate the general needs of the show when performed at different auditoriums rather than the specific needs of the theatre where the show w Road Show A show which is and is not based at any particular theatre, each performance staged at a different venue, as opposed to a show at a repertory theatre. robotic light moving lights rock board Lighting board used for rock concerts. These generally afford more 'hands on' control of the light than theater control boards, and though they use computer memory they allow groups of light and sequencing effects ('chasers') to be assigned to manual fade Rock Concert A rock music show with a star or well known band, often performed outdoors in locations such as parks, open-air amphitheatres or football grounds. Rock concerts are always road shows. rods Light-sensitive cells in the retina of the eye, essential for vision in dim light and not sensitive to color. rhodopsin, cones Rolls Rolls of filters. A roll is normally 117 x 400 cm. Rondel (roundel) A round, convex, heat resistant, glass, color filter primarily used on some boarder lights or footlights; also available as clear cover glass. Rosenthal, Jean Pioneer American lighting designer and consultant, who revolutionized dance lighting by using expressive angles from the side and back as a basis, and revolutionized all stage lighting by approaching it systematically as an aid to expression of the produ roundels rondel RS-232 ANSI recommended data communications interface standard designed to connect computer terminals to data communications equipment such as modems. Its use is limited to distances of about 20 meters and can only connect one receiver to one transmitter. Other run-through A rehearsal in which the show is run in sequence on stage with all elements (actors, lighting, scenery changes, choreography, music, sound, props and so on), with as few interruptions as possible. safety chain Steel chain used to attach hanging equipment to the support structure as a safety support in case of failure of the primary hanging support (clamp etc.) safety mesh Metal wire mesh placed at the front of a luminaire to retain broken glass if the lens breaks. safety bond safety chain salt-pot dimmer liquid dimmer Samoiloff effect Lighting effect created by Adrian Samoiloff in the 1920's based on the effect that primary colors appear black when illuminated by different primary colors, thus a man with red face paint appears white under red light and turns black when the light change saturable reactor dimmer A development of the autotransformer dimmer where a DC low voltage current saturated the transformer core gradually thus negating the back EMF and dimming up the lamp load. This was one of the first attempts at dimmer regulation by use of a separate contr Saturation: A property of color which defines the amount of white mixed with it: a pure red is known as completely saturated while pale pink, which is red mixed with white, is of low saturation. Saturation rig A lighting system used in repertory theater to prevent repositioning of luminaires and save time during show changeovers: Luminaires are hung in all possible positions to provide several washes and specials from any desirable angle Savoy Theatre London theater opened in 1881 which was the first theater to be illuminated by electric lighting. Saxe-Meiningen, Duke George II von The Duke assisted by actor Ludwig Chronegk directed a troupe of actors resident at his court in productions with historically accurate costumes and scenery and expressive mob scenes. The productions were widely influential in the development of realistic Scale Plans Plans of the theatre, scenery or lighting drafted in a predetermined proportion to the actual size of the stage. Accepted scales in theatre are 1:50, 1:20 and 1:25.Lighting Plans Lighting Plot, Layout, Ground Plan, Sections Scale Symbols Symbols of instruments and accessories in a predetermined proportion to their actual. Accepted scales are 1:50, 1:20 and 1:25. Most templates of symbols are at a scale of 1:50 or 1:25. scene master preset master scene preset Scenic Designer The person in charge of designing the set for the show. In some cases, the scenic designer is also the costume designer. After completing the design of the set, the scenic designer prepares scale plans (ground plans and cross sections) which the lighting Scenic Projector Effect Projector Scenographer The person or people in charge of the overall visual concept of the show (including scenery, costumes and lighting). This is often the scenic designer, working in collaboration with the lighting designer, costume designer and director. Schedule 1. The advance planning of time distribution and deadlines for various aspects of the production. Schedules are used at all stages of the production, and can be general, in terms of weeks or months, or specific in terms of a particular technical rehearsal Timetable Schema A group of instruments or of lighting elements which when lit in conjunction with each other signify a place, location, season, time, mood, atmosphere or any other recurring motif. Sciopticon An optical effects projector for moving effects. In principle, it is similar to slide projector with a continuously moving slide. Scoop A deep floodlight with a diffuse, generally elliptical contoured reflector; the field angle commonly is less than, 100?. scotopic vision Vision where the rods in the eye are the principal receptors. It occurs when light levels are low and color cannot be perceived. SCR ( Silicon, Controlled Rectifier) A solid state semiconductor device operating as a high-speed switch which is the heart of most modern dimmers. Screen Gain The ratio of the luminance of a screen to the luminance of a reference screen which (1) reflects all of the incident light and (2) reflects it uniformly in all direction , i.e. has a uniform luminance in all directions. The gain of an actual screen will Screen Lumens: The quantity of light flux reaching the screen from the projector. screw base A cylindrically shaped threaded lamp base: one contact is at the bottom of the base and the other is the threaded area. screw cap screw base Scrim In film and TV lighting: a flag made of translucent material, such as gauze, or glass fabric, and used to diffuse or soften light; also available as half-scrim to cut intensity of only one half of the beam usually with wire screen. In theater: a gauze cu scroll color changer scroller scroller Color changer which consists of a roll of gels taped together in a string which is wound around two cylinders. A motor, generally controlled by digital commands from the lighting board, turns one or both of the cylinders to position the desired gel in fro sculptural light Light from the side or rear of an object which enhances its three-dimensionality. Sealed beam lamp PAR lamp Sealed Beam Spotlight PAR lamp searchlight Luminaire with an extremely intense concentrated beam. These usually have parabolic reflectors and discharge lamps and may be motorized to cast moving beams across the sky. Recent models have DMX control of parameters such as movement, focus and intensity secondary colors Colors produced by additive mixing of two primary colors. In light these are blue-green, yellow (a mixture of red and green) and magenta (a mixture of red and blue). segue Used in theater to indicate continuity, originally a musical term for one musical number to follow another. selective reflection Reflection of only part of the incident wavelengths. Colored objects illuminated with white light selectively reflect only wavelengths of that color. selective transmission Transmission of only part of the incident light, for example red color filters do not transmit a large portion of blue and green light. selective visibility Illumination only of a specific part of the stage picture, as opposed to general illumination. Selector Switch System A cross connect system using multiple position switches . semaphore color changer A color changer with filters in neighboring frames which are lowered in front of the light. More than one filter may thus be used at once, however the sum total of filters is limited due to physical unwieldiness, and mechanical problems such as frame warp semiconductor transistor Senior Fiver Sequence Transition from one lighting state to the next in sequential numeric order. Series Circuit A series circuit is one in which the current has only one path to take--from one side of the source, through the load, and back to the other side of the An example for series circuit is the use of low voltage lamps like A.C or MR lamp. The disadvantage of Series-Parallel Circuit Series-parallel circuits are those that can be identified as having some components in parallel with each other, where the parallel combinations are in series with other components. Connecting a switch and fuse or circuit breaker in series with a source a Serlio, Sebastiano (1475-1554) Italian painter and architect who published a treatise on architecture. One section of this deals with lighting Service Life Lamp life in service as affected by voltage variations, vibrations, shock, excessive heat conditions, etc. rated life servo control board Motor-driven dimmer banks with electromagnetic clutch systems used to use servo circuits to cause a dimmer to de-clutch when reaching its predetermined (preset) level. Set Dressing Lighting the scenic set. Set-Light Separate illumination of background or set other than that provided for Principal subjects or areas. sharkstooth gauze Thick gauze material used for transparency effects. sharkstooth scrim sharkstooth gauze Shin Buster Light from the floor at the sides. Often used in dance to emphasize movement of the dancers? bodies. short circuit When direct electrical contact is made between the live conductor in a circuit and the neutral or ground, current in the circuit will rise because its path has been made shorter rather than having to go through the load. This should cause a fuse to blow o short-arc lamp High pressure discharge lamp with an arc which is small compared to electrode size. Short arc (compact arc) lamps filled with mercury or xenon have high arc luminance and are useful as projection sources. Show Any form of performance, including drama, dance, rock concerts, operas, musicals and so on. show control Term increasingly used for a control setup where several systems are to be controlled in coordination, such as sound, lighting and scenic effects. MIDI show control Show Manager The person in charge of the smooth running of the show. The Show Manager must be familiar with every operational detail of all departments: lighting, scenery, acting, props, wardrobe, makeup, sound, stage management and so on. Shutter Movable metal gates used within a lighting device or projector to block light, e.g. the elements used to shape the beam of an ellipsoidal spotlight. SI unit (Systeme Internationale d'Unites) Internationally agreed coherent system of units derived from mks system. The seven basic units are: meter, kilogram, second, amplere, kelvin, mole and candela. Derived units include Hertz, Lumen, Lux ,Watt, Volt, Ohm and Side Back Light Illumination of the subject from behind to produce a highlight along its pictured edge; light is from a direction substantially not parallel to a vertical plane through the optical axis of the camera or view. Side Positions Hanging positions at the side of the stage (ladders or balconies) or FOH side hanging positions on the walls of the auditorium. sidearm boom arm Sidelight Light from the side of an actor facing the audience. Sidelighting is often used in dance, as it emphasizes the entire body and movement. Diagram, photo, Toplight, Backlight, Frontlight, Crosslight, Footlight Signal-To-Noise Ratio(S/N) The ratio of the strength of a wanted signal to that of the undesired background signal. silhouette 1) A dark figure against a light background, for example dancers against an illuminated cyc. 2) Variable-beam profile spot manufactured by CCT. silk 1) Theater: Diffusion filter resembling frost with stripes, which spreads the light in a designated direction. 2) Film and TV: Bright translucent diffusion material which must be used in holders to keep a distance from fixture heat, and usually made of c Sky Pan: A very shallow scoop or floodlight of extremely wide beam spread, generally near 180?. skycloth Backcloth painted blue to represent the sky. slave unit master/slave slide Photographed or painted projection material. Common sizes are 35mm, 180mm and 240mm, depending on the projector to be used. Slide Light Lighting from the side to enhance subject modeling and place the subject in depth; apparently separated from background. slide projector projector slider Fader or lever on control board. slider dimmer Dimmer where a slider made varying contact, either with a resistance winding as in many resistance dimmers or with a transformer winding in autotransformer dimmers. sliding tee hollow metal device with screws set into its side, which fits over a metal pipe where the screws lock it in place, and has an attachment at its side for rigging luminaires. smoke effects Smoke may be produced onstage by pyrotechnics or by smoke machines. The smoke can vary from a low lying white cloud-like affair produced by dry-ice machines, to the faintest of hazes used only to make light beams visible. pyrotechnics, smoke machine, dry ice smoke gun smoke machine smoke machine Machine for producing smoke. Most smoke machines use a proprietary smoke fluid which is heated within the machine and expelled by air pressure to create clouds of smoke or a light haze. smoke pellet Small pellet which when ignited, usually electrically, produces smoke. SMPTE Time Code: Standard protocol developed by SMPTE (Society of Motion Picture and Television Engineers) which breaks time down into hours, minutes, seconds and frames. Used to synchronize different devices, for instance to lock a tape recorder to a video recorder. SMX Standard protocol developed by Strand as an attempt to overcome the faults of DMX 512; more complex and more expensive than DMX and has not been implemented by companies other than Strand. snap cue Cue executed in an instant. snoot Short black metal cylinder added to the front of a luminaire to control spill light and hide the lens. Also known as top hat. Socapex connector Multipin connector used with multicore cable for lamp as well as control wiring. Many dimmers especially for touring use are built with Socapex sockets. Socket Number A specific number designating the socket to which each instrument on the lighting plot will be connected. sodium lamp Discharge lamp containing sodium gas, which produces a yellow color. Low-pressure sodium lamps produce a very efficient monochromatic yellow light. High-pressure sodium lamps are less efficient but produce a broader spectrum and better color rendering. soft edge A fuzzy beam pattern edge which is indistinct. soft patch Control patch; interconnection of dimmers and channels. This may be done with a pin matrix but is a common internal function within computer control systems. Soft-Light A well-diffused light source which produces soft or poorly defined shadows when an object is placed in between the luminaire and the light background. Solid State A general term for a device which functions through the use of semiconductor devices in place of vacuum tubes or in place of transformers. solo Function on rock control boards which leaves the selected light on and turns off all the others. son et lumiere Sound-and-light show, usually performed outdoors at night at historical sites, and coordinating tape with lighting and projection effects. Special An instrument which is accurately focused onto a defined spot on stage For instance the location where an actor gives his monologue, a piece of furniture etc. Special Effect Fire, lightning and other unusual lighting effects which may require special equipment. Specific illumination: illumination of localized areas by means of controlled illumination. Spectra (Line spectra) Atoms excited by a supply of energy from an external source emit light of well-defined frequencies. When the atom is excited, the electron jumps to a higher-energy orbit farther from the nucleus, and as it falls back to its normal orbit, it emits a discre spectral distribution The colors produced by a light source spectral distribution curve spectral distribution graph spectral distribution graph A graph displaying the spectral distribution of a light source. spectral hue A hue found in the natural spectrum, which may be seen for example when white light is broken up by a prism. nonspectral hue Spectral Power Distribution (SPD) A plot showing the relative amounts of power at the various wavelengths for a particular light. spectrogram spectral distribution graph Spectrom Atoms excited by a supply of energy from an external source emit light of well-defined frequencies. When the atom is excited, the electron jumps to a higher-energy orbit farther from the nucleus, and as it falls back to its normal orbit, it emits a discre Line Spectra spectrophotometer Photometer which compares two light radiations wavelength by wavelength. spectroscope Instrument for the observation of spectra spectrum arrangement or display of light or other forms of electromagnetic radiation separated according to wavelength, frequency, energy, or some other property. Dispersion, the separation of visible light into a spectrum, may be accomplished by means of a pr Specular Description of a mirror-like surface. When used to describe a light, it implies a hard light specular reflection Regular reflection in accordance with the law of reflection, that is, the angle of reflection from the surface is equal to the angle of incidence of the light. speed of light A universal constant, equal in a vacuum to approximately 186,281 miles or 300,000 kilometers per second. spherical reflector Reflector whose surface is part of a sphere. When a light source is located at the center of that sphere its light will be reflected back through the source. Spider Electrical distribution device that usually breaks down the feed from the source to individual circuits. spigot Male suspension hardware attached to the yoke of a luminaire to allow it to be fixed to a floor stand or other female suspension unit. spud Spill Undesired light from an instrument. When an instrument is focused, the beam sometimes hits an undesired element or area, such as the wall of the auditorium. This is usually corrected using barndoors or shutters. Sometimes there is spill from the ventilati spill light spill Spill Shield Louvers Split Non synchronous transition from one lighting state to the next. split color frame Color frame with sections of different colors in it. This may produce a varicolored beam, or may produce a third color by additive mixing, depending on the type of spotlight used and on its focus. Also called broken color. split fader A crossfader consisting of two faders. One fades out the previous state and the other fades in the new state. splitter Device used with long runs of communications cable to boost the current as well as to route it in various lines. Spot 1) Concentration of the light into a restricted area. This term is used both to describe the character of the light and in focusing, to indicate concentration of the beam in a Fresnel or PC instrument. 2) Slang for spotlight. Spotlight Any of several different types of luminaires with relatively narrow beam angle designed to illuminate a specifically defined area. In motion pictures, generic for Fresnel lens luminaires. spotlighting To narrow the beam of a spotlight, or more generally to emphasize something by means of light. Spread to Flood Transition from a concentrated area to a widely lit stage. Spud spigot square law dimming Dimmer whose light output (not voltage output) is the square of the fader setting. Thus a fader at 5 or half will give 25% light output and 158V in a 240V system or 79V in a 120V system. A fader at 7 wil give 49% light output and 194V in a 240V system Squeeze Ratio The horizontal compression of an image on film by an anamorphic lens in wide screen systems. Stage Hand A person on the stage crew, usually employed in the montage and dismantling of scenery, and in moving and operation of parts of the set during performances. Stage left and stage right To the actor's left and right respectively as he faces the audience. Stage Manager The person in charge of all activity on-stage in preparation for performances and during them.The Stage Manager must be familiar with every operational aspect on-stage: lighting, scenery, acting, props, wardrobe, makeup, sound, assistant stage managers an Stage Plug A flat two-or three-conductor connector. stage right Actor's right as he faces the audience. Stage Tower A tall construction over the stage, with a grid and pipes with which scenery and lighting can be flown into the tower and lowered onto the stage as needed.The Stage Tower is usually at least 2.5 times higher than the proscenium arch, so as to enable scene Stand An apparatus which is secured to the floor and on which one or more instruments or other equipment can be hung. There are various types of stands, the most common being the tripod. There are also heavy base stands which can be secured to the stage. Photo stand by Accepted term for warning signal given by the stage manager shortly before a cue must be executed. Stand-ins Usually members of the technical crew who fill in the place of actors during plotting sessions and parts of technical rehearsals when the actors themselves are not required on-stage, but it is necessary to indicate the mise-en-scene of the show on-stage. standard candle Former unit of luminous intensity today expressed in candela. standard source energy spectrum standard white source energy spectrum stars effect Stars may be produced by gobos,a mirror ball, or most successfully by fiber optics one end of which is connected to a light source with moving wheel to cause a flickering effect, and the other end pushed through a black curtain. starter Electronic device which produces the high voltage necessary to ignite the arc in a discharge lamp. Stelmar spotlight Early British profile spotlight used with a carbon arc as a follow spot and with incandescent lamps as a spotlight. Behind the source was a spherical reflector, and between source and gate was an objective lens and two concentric ellipsoidal reflectors. stencil Plastic template with outlines of lighting instruments to convenient scales used in drafting lighting plots. Step lens A lens that acts similar to a plano-convex lens but is thinner and lighter due to steps; term often used when a lens is stepped on the plano side and is without diffusion distinguish from a Fresnel Lens. stereoscopic vision Vision from two eyes. Differences in perception from each eye aid perception of depth. stray light Light which is not where it should be, or rather is where it should not be. May be caused by spill from lamps or reflection from bright or shiny surfaces. strip lime To close the top and bottom shutters of a follow spot while flooding it as much as possible, so that the stage is covered by a strip of light cut off above the actors head and at floor level. Striplight A luminaire with a number of lamps arranged in a line. Often each lamp is in an individual compartment. There may be a reflector behind the lamp and/or a color media in from of the lamp. Striplights are normally wired in three or four circuits. strobe light A luminaire which emits rapid pulses of intense light. Usually with a xenon light source and electronic circuit to create pulses, and variable speed control. Often used to heighten a slow-motion movement sequence. Certain pulse frequencies may cause epile stroboscopic light strobe light stud-contact resistance dimmer A type of resistance dimmer with a set of separate resistance coils connected to a series of stud contacts. Brushes on an insulated holder at the end of a radial moving arm make the contact. Style The combination of signs generated by various artistic means, which characterizes the form (as opposed to the content) of a work of art. Styles in Lighting: Realistic, Symbolic, Expressionistic, Pictorial, Theatrical, Personal subjective brightness Brightness as perceived by the eye is not the same as objectively measured brightness, and is influenced by adjacent surfaces, adaptation of the eye, etc. submaster Fader on computer control boards which controls a light or group of lights, often independently of the cue currently on playback. Subtractive Color Mix The removal of energy of various wavelengths from a light, e.g. by filtering or reflection. When colorants(paints, dyes, etc.) are mixed or when filters are superimposed, each tends to remove energy at the wavelengths it would have it acting independently sun burner An auditorium light in the age of gas located in the center of the auditorium ceiling. Svoboda, Josef Czech pioneer of scenography (born 1920) famed for his work with multimedia with the Laterna Magika, then for innovative and creative use of projected scenery, and use of light as an integral and striking element of the scenic design. Svoboda unit Narrow-angle luminaire which casts a strong rectangular shaft of light, and consists of nine 24V sealed beam lamps wired in series. Swan, Sir Joseph Wilson (1828-1914) English physicist and chemist who produced an early electric light bulb in 1860. The bulb utilized a filament of carbonized paper in an evacuated glass bulb. Lack of a good vacuum and an adequate electric source, however, resulted in a short lifetime for Swatchbook A small booklet including samples of all color filters manufactured by one company. Swatchbooks include photometric data, in graphs or percentages, regarding the amount of light and wavelengths transmitted through each filter in the range. Swatchbooks are switch Device for opening or closing a circuit thus allowing or preventing current flow. Switchboard A switch panel, control board or console of any type. A portable control board of the 'Piano-Box' type. Switching Patch Symbol Libraries Specially designated CADD or computerized lighting drafting programs have libraries of symbols of all instruments. These can be organized by type of instrument or manufacturing company. Some programs also have libraries of photometric data. In a simple CA Symbolic Lighting An independent style of lighting where schemas and colors all have their own symbolic import, signifying a place or a mood, serving as a metaphor and so on. Symbolic lighting can be incorporated into almost any theatrical genre. Photos, visual examples: Symbolistic Theatre Symbolic theatre is an anti realistic form which interprets the world neither logically nor directly, preferring to use symbols and allusions to provoke emotions and moods. symmetric flood Floodlight with symmetrical reflector synoptic display Display affording a general simultaneous view of the whole. stage after the scenery has been erected and the lighting rigged. T lamp The code T represents tubular shaped incandescent lamps intended for use in theater luminaires. They are manufactured in wattages of 500-2000, produce a color temperature of 2,900 K-3,050 K and have a long rated life.They were first introduced in theater tab warmers curtain warmers tadpole tail tallescope Vertical extending ladder with a small platform at the top and a base with wheels which can be adjusted to compensate for different floor heights or rake. tallow candles Candles made of tallow, a white solid produced from cattle and sheep fat. TC (time code) SMPTE TC Technical Crew All people involved in technical aspects of the production: stage management, wardrobe, makeup, props, lighting technicians, stage hands, sound technicians and so on. Technical Rehearsals Rehearsals which take place on stage utilizing technical elements of the performance. The term Technical Rehearsal is also used to describe the first rehearsal on stage (also known as the Tech) in which all elements of the production Telecine The broadcast phase of television concerned with television cinema originating both from film and from videotape. telephone-exchange patch panel A patch panel with jacks connected to the circuits and sockets connected to the dimmers. temperature A measure of heat, or specifically that property of a body which determines the heat that will flow in or out of it to a neighboring body or region. In theater llighting the Kelvin scale is used to describe color temperature. The Kelvin scale has degrees Template 1) Gobo, a cut out metal shape inserted in the gate of a profile spot so that the shape will be projected. 2) A cut-out ruler including all symbols (instruments, accessories and electricity), used trace the symbols onto the lighting plot. Tenner (or Ten-K) A ten-kilowatt Fresnel fixture. tenth-peak angle That part of a light beam whose intensity is 1/10 of the peak intensity. field angle test lamp Lamp with two exposed leads for circuit testing Texture Surface Treatment textured light A gobo wash used along with general light which breaks up its uniformity. TH (tungsten-halogen) lamp Lamp consisting of a tungsten filament and quartz envelope filled with halogen gas. When particles of the filament evaporate they join with particles of the gas and are eventually redeposited on the filament thus extending lamp life, and preserving bright theatre in the round arena stage Theatrical Lighting A style of lighting which exists in its own right, making use of light effects, and becoming an overt part of the theatrical message. Theatrical lighting can be impressive in its use of effects which are possible and justified only within the theatrical c three-color system (trichromatic theory) The idea of three basic kind of cones in the human eye: red-sensitive, gren- sensitive, blue- sensitive. This theory explain what happens in the photoreceptors under direct light stimulation. The theory was developed first by Thomas three-phase current Current generated in three phases by a generator. In theater lighting equipment is connected between each phase and the neutral, and no use is made of the higher voltage between two phases. Care should be taken however to balance the lighting load between throw distance Distance from the luminaire to the area it is to light. throw throw distance thrust stage A stage which thrusts into the auditorium, that is, a large part and occasionally all of it is surrounded on three sides by audience. Thumb Sketches Miniature (stamp-size or larger) very rough sketches demonstrating initial ideas or concepts.Thumb Sketches are a useful way of working out or demonstrating ideas without having to go into precise or technical detail. thyratron A thyratron is a gas-filled electron tube that can rapidly switch large electrical currents. The tube has a high electrical resistance, and no current flows between the tube's cathode and plate. A small electrical current applied to one or more control el thyratron tube dimmer Early remote-controlled dimmer introduced in 1947 by George Izenour which used a pair of thyratron tubes connected in inverse parallel. These dimmers were not load sensitive and gave a smooth dimming curve but produced a great deal of heat and were noisy thyristor (combination of the words thyratron and transistor) any of several semiconductor devices that act as switches, rectifiers, or voltage regulators. Known as silicon-controlled rectifier. The SCR is a semiconductor component made from four layers of p- and tilt Up-and-down movement of a luminaire. Used with 'pan' (sideways movement) to describe movement of moving lights. time code (TC) SMPTE TC Timetable Schedule tint Unsaturated color tonal light toning light toning light A wash of colored light to bring out the color of a set or subject onstage. top hat snoot Top Sidelight Light from a high, steep angle from the side top-and-tail technical rehearsal Technical rehearsal where lengthy speeches are cut short and only the cue lines spoken. Toplight Light from above the actor, the beam perpendicular (or nearly so) to the stage floor.Toplight can be used for instance to help attain plasticity, for a special or for a color wash without the light directly hitting the scenery. Diagram, photo: Backlight, torch 1) A hand-held stick with a flaming end 2) British for flashlight torchlight Light cast by a torch. Tormentor Light: A spotlight mounted on a boom or ladder just off-stage from either tormentor (downstage wing) Tower: A fixed or movable high stand or platform on which to mount fixtures, generally with a built-in ladder. Track Sheet A table indicating the dimmers (or control channels) and their intensities in each cue during the show. This gives the lighting designer an immediate reference of the manner in which the instruments are used throughout the show. tracker wire The link between a liquid or autotransformer dimmer and its control handle. tracking Following a channel through the course of the show. Used in computer boards as1) a function which charts the changes in a channel's level through a specified sequence of cues and 2) a function which enables changing a channel level and then having it chan tracking sheet track sheet transformer Voltage-altering device for alternating current, consisting of an iron core wound with two coils of wire each electrically isolated. Alternating current through the primary coil produces an alternating magnetic field in the core which in turn induces curr transistor Semiconductor device that can be used as a switch, rectifier, or current or voltage amplifier. Bipolar transistors depend on the flow of both majority and minority carriers whereas in unipolar transistors current is carried by majority carriers only. A bi translucency A translucent material; or the property of being translucent. Translucent: A material that permitting transmits light but breaks up the rays so that an image cannot be seen clearly through the material. transmission Used in lighting to refer to the amount of light passing through a medium. Transmittance A measure of how effectively a material will transmit light, i.e. is defined as the ratio of the transmitted lumens to the incident lumens on the material. When reflection losses are ignored, the term internal Transmittance is sometimes used. transparency The property of being transparent; A transparent material. Also may refer to material used in overhead projectors. Transparent: A material that absorb very little light and transmits very nearly all the light without breaking up the rays of light. If the surface of such transparent materials are polished, the light pass through as a definite beam. Tree: A high stand or tower with horizontal arms on which to mount fixtures. triac Current-regulating device similar in effect to a thyristor but which uses a pair of rectifiers in a single device. Less expensive than thyristors but considered by many to be problematic in dimmers. tripe Electric cable in the flies connecting lighting bars to outlets at the sides of the stage. tripod Three-legged stand. Truss A strong and sturdy construction which is easily erected and dismantled, for hanging instruments in rock concerts and any other provisional stages.. Trusses are manufactured in various shapes and forms, so that the manner and combination in which they are tubular lamp T lamp tubular ripple Lighting device which produces a water-ripple effect, consisting of a light source surrounded by a revolving tube with wavy slits cut in it. tungsten filament The tungsten wire, usually coiled, in an incandescent lamp, whose resistance to the passage of electricity causes it to emit light. tungsten filament lamp Light source consisting of tungsten filament attached to lamp base, sealed within a glass envelope which is filled with an inert gas, usually argon or krypton. tungsten-halogen cycle Particles of the tungsten filament of a TH lamp evaporate to combine with molecules of halogen gas. These are drawn to the heat of the filament where the tungsten is redeposited to become part of the filament, thus producing a theoretically immortal lamp. twist-lock connector Trade-marked name describing commonly used connectors which are locked together by being twisted around. Twofer A load connector wired in parallel to two line connectors so that two lumiaires can be connected to a single electrical circuit. UL Underwriters Laboratory Ultraviolet: Radiation which is of the same basic nature as light (i.e. electromagnetic energy)but of wavelengths too short to be seen by the eye. Sufficiently short wavelengths will cause sunburn, irritate the eye, etc. Wavelengths close to the visible spectrum (i/e Underwriter's Laboratories (UL): An independent American testing laboratory that will test equipment to see if it meets certain safety standards when properly used. Unit A name applied to theatrical type luminaires, basically jargon for lighting unit. upstage Towards the rear of the stage, farther from the audience, so called because stage floors used to be raked and the rear end was higher. USITT Graphic Symbols A set of graphic symbols denoting the various theatrical instruments and lighting plot indications, defined by the USITT and the ABTT, aiming to create an objective international language of symbols which does not advertise the equipment manufactured by a USASI American National standards Institute variable beam profile spot variable lens luminaire variable lens luminaire Luminaire (usually profile spot) with two lenses whose differential movement allows change in beam spread and focus i.e. sharpness of beam edge. Variac Trade name for a brand of rotary autotransformers VDU (visual display unit) Monitor screen used with computer control boards to display information about channels, cues, timing etc. Display functions vary in different boards. video projector Projector of videotapes; two basic types exist: 1) Projector containing three cathode ray tubes, each tuned to contain a different primary color,. Light from the three CRT's is collected by lenses and focussed on the screen. 2) Xenon projectors with vacuu virtual reality Computer technique where the viewer by wearing special goggles has the illusion he is within the environment on his screen. Can be used as a design aid. visibility The ability to be seen by the audience, and one of the major purposes of stage lighting. visible spectrum That part of the radiant electromagnetic spectrum to which the human eye is sensitive, ranging in wavelength from about 4 x 10-7 to 7.7 x 10-7 meters. The entire range when perceived together is white light, while colored light is a narrower range of w visual angle The angle formed by the lines connecting the outer extremes of the viewed object and the eye. visual field The human eye can see about 185 degrees horizontally and 160 degrees vertically. visual perception Perception by means of light reflected from objects which strikes the eye and is processed and interpreted to the brain. visual threshold Minimal amount of light required to detect an object. visual acuity The relative ability of the eye to resolve detail. Expressed as the reciprocal of the minimum angular separation in minutes of two lines just detected as separate and that forms in the human eye an angle of one minute. visual cue A cue which is to be executed beginning at a specific stage action rather than spoken text. volt The unit of electric pressure, or electromotive force (emf), defined as the difference in electric potential between two terminals that will cause a current of one ampere to flow between them through a resistance of one ohm. voltage Electric potential expressed in volts. In the U.S. mains voltage is 110V while in Europe and the U.K. it is 220 to 240V. voltage drop The loss of current in volts that occurs through energy wastage when a current passes through a cable or electronic device. Ventilation Holes Holes or slots in the casing of lighting instruments, designed to ventilate the instrument and to enable the heat generated by the lamp to escape. Sometimes there is spill from the ventilation holes. This is usually corrected using black wrap (taking care Visibility The degree to which small details can be discerned by the audience. Visibility is one of the main concerns of the lighting designer. At times visibility is ?sacrificed? in favour of atmosphere, modelling or selectivity. Illumination Wagner, Richard Wagner, Richard The greatest composer of German opera (1813 - 1883). (I PROTEST. WHAT WAS MOZART, NUMBER TWO? JUST BECAUSE BENTZI PREFERS WAGNER????) Richard Wagner, devised a new form of 'music drama' in which text (written by him self), score, and stagi Wagner, Wolfgang Wagner, Wolfgang, Richard grandson run the ?new? Bayreuth Festspielhaus after the war. in this attempt to make a clear break with the past after the debasement of Bayreuth under Nazis, he was the first to embraced Appia?s theories in full and presented s wall slot Lighting position at the sides of the auditorium. Warm Color One of the color, generally in the range of yellow-orange-red, on the long end of the spectrum. These colors are perceived by the spectator to be warm in appearance. ?Warm? color is associated with excitement and stimulation. 'Warm' light sources are of l Warm Colors Red, orange or yellow light (in various hues and values), generated by using filters which enable penetration of light in wavelengths of 450 to 600 millimicron. Color wheel, photo section on color Wash Color Wash Flood Wash Even, overall light on performance space or background wash of light over entire performing space, like class room or office illumination, where the primary objective is maximum visibility. washed stage Evenly illuminated stage. watt In electricity: the power formula used to describe the rate of energy use in electrical circuit. The energy available in any electrical circuit (watts) is the product of the amount of electron flowing (amperes) times the pressure of their flow (volts). Th wattage Amount of power expressed in watts; we say the power of consumption of a lamp is 1000w. wavelength A wavelength is the distance between crests in a wave of energy. wavelength in the visible spectrum are measured in manometers, each of which is only one billion of a meter. difference between colors involve tiny difference in wavelengths. waves effect ripple effect wax candle waxes are mixtures of heavy hydrocarbons and fatty acids combined with esters (organic salts) of alcohol?s instead of with glycerol as in fats and oils. Wax was used for making candle. ways channel Welsbach burner Incandescent burner developed by Welsbach in 1885. It was nearly the final development of the gas industry who tries to compete with the birth of the electric light. White An achromatic light , i.e. without hue; and achromatic surface of high reflectance white light equal energy spectrum white light white winch Any of various machines or instruments for hauling or pulling.A winch is a powerful machine with one or more drums on which to coil a rope, cable, or chain for hauling or hoisting : wing lights Lights positioned in the wings. wing pole Poles used in the age of theater lighting by candles. They were placed upstage of the wing flats and held candles and reflectors. Dimming of the light was achieved by turning the poles so the candles faced away from the stage. Wings Areas on SL and SR not visible to the audience with immediate access to entrances and exits to the set. In the wings the actors prepare for entrances and the technical crew operates the performance. wired-in dimmer Dimmer in a bank of dimmers who is permanent install; the other type is plug-in dimmer. Work Lights A general lighting system permanently installed in the studio or stage production area, which provides sufficient illumination for moving scenery and general work when the production lighting system is not in use. working lights A Lighting system on stage area or audience area, providing working light during setup or rehearsal. worklight working lights X-rays A striplight mounted above the acting area. xenon arc A heavy, colorless, and relatively inert gaseous element that occurs in air as about one part in 20 million by volume and is used esp. in thyratrons and specialized flash tubes. A discharge type of lamp that boasts the highest lumen per watt out put of an XLR connector Fife pin connector use to link between the control board and the dimmers or other device control through a DMX512, only three pins are used for a single DMX link; the other pair of pins is used to send dimmer rack information (like temperature) to the con yoke The suspension frame or fork hold deferent type of luminaire. The yoke as two movement direction; pan and tilt Young, Thomas. Young-Helmholz theory 1773-1829. English physician, explain in 1801 a new theory on color sensation as due to presence in retina of structures corresponding to colors red, green, and blue. His theory modified later by Helmholtz and known as the Young-Hel zoom A zoom lens is one with a focal length that may be varied; it is also called a variable-focus lens. The zoom lens used in profile spots and effect projector as well as moving spot and other. The zoom lens consists of fixed and movable lenses. The focal le variable zoom