Color scroller

A color scroller or color changer is an electro-mechanical lighting accessory used in theater, film, dance and concerts to change the color projected by stage lighting instruments without the need of a person to be in the vicinity of the light. A color scroller moves plastic "gel" color gel [actually dyed polyester and/or other base materials coated with dyes] into the beam of the light. It is generally attached to the gel frame holder at the transmitting end of a lighting fixture, so color is introduced after the beam characteristics have been defined by the optics of the lighting instrument. Most scrollers are controlled via DMX512 protocol, but some models (e.g. Wybron's Coloram IT) also utilize the RDM protocol. When color scrollers were first introduced around 1980, a number of companies produced them, including: Avolites, GAM Products, Morpheus Lights, Rainbow, Rosco Laboratories and Wybron Inc. Now the main manufacturers are: A.C. Lighting, Apollo, Morpheus Lights and Rainbow (in alphabetical order).[1]

The most commonly used type of scroller is the single string scroller. This type has only one string of color anywhere from 2 to 33 frames long.

Dual string scrollers use 2 strings (one behind the other) and allow for a form of CMY mixing. The Apollo MXR 2, Chroma-Q Cascade and the Wybron CXI use 2 gel strings to obtain a CMY mix. One frame of clear gel is positioned at the center of each gel string (50% DMX) with progressively denser frames of color positioned to either side of it. The first string has progressively denser yellow and cyan frames and the second string has progressively denser yellow and magenta frames. This permits various YC, YM, and CM combinations to be achieved as a "static" color mix. There is a limited ability to transition "live" between mixed colors - although some transitions cannot be accomplished without passing through the clear center frame.

Finally, there are "true" CYM mixing scrollers that utilize three independently controlled gel strings - namely, the ColorFader system manufactured by Morpheus Lights of Las Vegas, NV. Independent control of the gel strings permits users to cross-fade "from any color to any color" directly (without going through undesired colors as on a single or double string color changer).

The "ColorFader" system was developed to mimic the dichroic systems used in most moving lights, creating smooth colour transitions. These transitions are achieved by starting with a full-density sheet of gel and then varying the color saturation by perforating the sheet to permit unfiltered white light to pass through. At the "start" position on a ColorFader scroll the holes are large and plentiful - so the percentage of white light predominates and low-saturation colors are achieved. As the scroll progresses the holes become smaller and fewer, the percentage of colored material in the optical path increases relative to the white light pass-through, and the result is progressively higher density color transmission. Ultimately a solid, unperforated sheet of gel is positioned in the optical path - for full saturation of and combination of Cyan, Magenta or Yellow.

...
Wikipedia