Profile-spots produce a fixed angle beam. The light
beam
can however be focused to achieve a sharp edge, or defocused to achieve a soft edge. The softer focused
beam
will be spread over a slightly larger area than a sharply focused beam, but in order to change the
beam
angle drastically, a different
lens
system of a different focal length must be used. The size of the
beam
depends on the focal length of the lenses which can be either a single
lens
or of a compound of two lenses . A narrow
beam
profile-spot uses a long focus lens, and consequently the unit will be longer than a wide
beam
profile-spot with a short focal lens.
The Shakespeare fixed angle profile spot by Altman.
Fixed angle profile-spots are available with
beam
angles in the range of 9O to 50O, and are designated by the
lens
parameters. For example, a 6X9 profile-spot will have a wider
beam
angles than a 6X12 (the 6 indicates the diameter of the lens, the 9 or 12 indicate the focal length).
European luminaires use both elliptic and spherical reflectors. Modern versions incorporate a bi-convex
condenser lens
to improve light collection at the gate - these are sometimes referred to as condenser spots. Recent extremely popular American luminaires use both a
condenser lens
and a cold dichroic reflector,
A dichroic reflector. The visible wavelengths are projected forward by the coating while most of the infrared light is transmitted backwards by the reflector.
which considerably reduces the operational
temperature
of the lamp. Thus a specially designed 650W lamp, which has an improved lumen output, can be used to produce an intense light, with
clear
optics and longer
lamp
and gobo life.
Most modern profile-spots have a flat-peak adjustment knob that enables alignment of the
lamp
in relation to the reflector. Thus the
light distribution
of the luminaire can be adjusted to a flat even field for projecting gobos, or to a 'peaky' field with a pronounced center .
Scatter of light which reduces the sharpness of the gate
image
can be reduced by placing a donut
mask
in the color frame groove .
The flat-peak adjustment handle of the Shakespeare by Altman.
Fixed angle profile-spots come in an enormous range of models. Typical theatre profile-spots come in the range of 650W to 2500W with
lens
systems ranging from 4 1/2"x8" to 6"x22".
