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Some Thoughts On Color Mixing

Over the years, many different lighting companies have come up with many different ways to do color mixing of their lights, and today I’d like to pontificate about some of the different methods and their strengths and weaknesses, and how they fit into different areas of design.

Flags: the mixing glass slides back and forth on tracks, moving into and out of the beam. The big strength of the flag system is the speed of the system, but what tends to happen is that as the flags ease into the beam, the gradations show up as visibly uneven coloration within the aerial beam. This isn’t always noticeable, especially during faster moves or on mixing cues where the flags move on an axis parallel with the viewing angle. It becomes especially noticeable as the colors get more saturated – the VL4000’s yellow flag is especially prone to this type of distinct unwanted “colored edge” effect. Certain zoom positions also tend to accentuate this, as well. It’s just harder to get a really smooth gradation with such short travel distances.

Wheels: the other big way to mix is with large gradated wheels, and the big advantage here is that you can achieve an extremely smooth field while mixing, at the expense of some speed – sort of. One of the ways to help improve the speed is to give the wheels a shortest-path algorithm, so for instance a common effect that might be applied to color – a 0% to 100% bump – the wheels would turn backward very quickly, throwing the saturated area and the clear area back and forth. This can lead to some weird results if the short-path algorithm isn’t turned off when it’s not needed.

There are a few other ways – some of Coemar’s lights used an unusual rotating flag system that kind of…rotated into the beam, but Coemar is the only light I’ve seen this on. The other obvious one is additive mixing with LEDs, and it’s easy to find examples of this in the myriad of LED wash lights and a few spot movers such as the Robe DLX.

To my knowledge, the shortest-path algorithm for wheels is only on Vari-Lite lights, and only on lights that came after the VL3000 series. (Much to my chagrin.) Ultimately, what informs the choice of a mix system has to do with what the lights will be used for. For aerial effects, I really, really want an evenly-colored beam in the air. This is important, because I like subtle color effects and creating pastels and other unsaturated colors, and I don’t want my beams to be two-toned as they’re pointing around the stage. Perhaps somewhat counter-intuitively, evenness in the beam is not nearly as important when you’re using those lights as a front wash on a band, where the overwhelming question becomes the quality of the light, because distance and optics smooth out aberrations by the time the light gets to a surface 30-40 feet away.

Colors matter, too. One reason I never (used to) spec certain High End lights is that I found their yellow too chrome-y and green, which might be nice for an EDM look but for everyday touring, I want something that doesn’t lean either too green or too amber, I want nice balanced colors, anything that leans too far toward warm or cool is no good.

The ultimate color mixing system would combine the speed of a flag system with the smoothness of a wheel. The shortest-path algorithm on the VL3000 color mix system would come close – the 3K’s color mix is very, very even, with the only noticeable transition happening as the wheel moved from the gradient to the pure color. The perfect mix system would do pastels and light shades like orange, lavender, and pale aqua perfectly, colors that have traditionally been difficult to do. Creating a clean pastel shade is just as important as the ability to do dark, saturated colors. That said, many people smarter than I have tried to create the “perfect” color mix system for a long long time, and I haven’t seen it yet. Vari-Lite offers a version of the VL550 specifically made for creating pastels and lighter “theatrical” shades, but to my knowledge no other lighting manufacturer has made a color mixing system specifically for lighter shades.

As far LED color mixing goes, I really hate straight RGB mixing, and I hate RGBW just a little less. The gaps in the spectrum are really unpleasant, the lack of amber light is particularly noticeable when trying to emulate tungsten – amber LEDs are still fairly rare, and their output is pretty abysmal compared to the other colors available.

It will be interesting in the next few years to see if the tech increases to the point where LED profile lights can have both a white output that equals that of an arc source and the brightness of LEDs in saturated colors, as well as finding doping materials that give us a vastly increased spectrum output. I’m sure we’ll bump into some sort of limit imposed by physics at some point, but it will be fun to see how far the technology can go as it matures.

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