Dimmers can have different characteristic fade patterns. The fade pattern of a dimmer is best described by the dimmer's dimming curve. The dimming curve plots the light intensity against the levels on the potentiometer scale. Dimmer curves usually plot the dimmer output voltage against the control signal level. The linear law curve

Some standard dimmer curves have been defined over the years for various purposes:

The Square Law Curve enables the light change to be evident mainly at the top end  of the potentiometer's travel. It is mainly used for television applications where the  bottom end of the travel is less important and does not have to be sensitive, since in  the studio blackouts are rarely a concern.

The Square Law Curve

The Cube Law  provides more sensitivity at the bottom end of the travel. This curve  is useful where highly controlled fades to blackout are of primary importance.

The Cube Law

The S Curve has a slow start at both the top and the bottom of the curve with a relatively steep middle. This provides a gentle start both when fading down from full  light and when fading up from zero. The S curve is the most popular dimming curve for  theatre SCR dimmers.

The S Curve

Programmable dimmer curves are available in some digital dimmers. Certain computerized lighting consoles enable selection or construction of the desirable curve  of any control channel. This function is useful for instance to create a curve for lamps  which require preheating or in order to adjust the curve of an unruly dimmer. Some  special lamps, such as fluorescent lamps, need specially tailored curves to attain a  smooth fade.

The Non-Dim Curve (Quick Dimming) is an extremely useful programmable curve essentially acting as an on/off switch for devices such as the motors of effect   projectors, smoke machines etc.

The Non-Dim Curve