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How does stage lighting color work?
August 14, 2010 1:08 PM   Subscribe

How does color-changing work in modern stage lighting?

When I was in high school, our shiny new auditorium had pretty fancy computer controlled lights. The color-changing part was just a series of gels on a roll that were rotated in front of the beam, to get various distinct colors. This meant you generally could only switch the colors while the light was off (otherwise you would see the intermediate colors), and it wasn't very fast. Neat, but trade-offs.

Last week, I went to a rock concert and clearly technology has moved on. In addition to the steerable lights, they had banks of lights that could change color instantly. (You can see them in this photo, the red and blue sets of four.) Generally they just used them to light the entire stage but one part of the show had them continuously cycling through colors.

So, how do they do that? And can anyone identify that light fixture?
posted by smackfu to Technology (9 answers total)
Could be LED.
posted by Monday, stony Monday at 1:23 PM on August 14, 2010


You know how your monitor has tiny pixels of red, green, and blue? Imagine that, but in a much brighter package.
posted by niles at 1:25 PM on August 14, 2010

I think they're something like this. It works more or less like a pixel on a TV screen or computer monitor -- each light contains a bunch of LEDs in red, blue and green. By turning the different colors of diode on and off, and varying their intensity, you can make any color in the spectrum.
posted by magnificent frigatebird at 1:29 PM on August 14, 2010

They are the i-Pix BB4 fixture. They are LED based. Hope that helps!
posted by spydee at 1:33 PM on August 14, 2010

Yes, the technology has moved on, but not as much as you might think. What you were probably seeing was something like a Vari-lite, which is a self-contained light that can be programmed to move, change color and swap out patterns on command and in rapid succession (fast enough that it's done while the lamp is on).

The color change is generally accomplished by a wheel inside with a number of color glass slides that can be spun in and out at a very high rate of speed...think of a wheel with 8 glass slides, and that wheel spins on an axis to deliver the color demanded by the programmer/designer.

The next generation of this sort of lighting is LED, which can deliver millions of colors in devices that can move the same way VLs can. I worked a show the other night that had some phenomenal lighting elements which had vertical LED panels hung at various heights and depths from a massive upstage video wall...the whole thing was amazing patterns and rapidly alternating photos and when viewed from the back of the house looked almost 3D, with vertical strips having popped out of the background and moving along with the background, only around and above the performers. Pretty crazy.

Despite the existence of Vari-lites (VLs) and others of their ilk, color scrollers are still somewhat common, though they are generally more trouble than they're you might expect, when a show is being loaded in and out every day and a half or so as well as being trucked all over the place, the delicate nature of a scroller makes it less practical, tho still cheaper. I've hung thousands of VLs over the years, and maybe one or two hundred scrollers in that same period. They're generally used for color washes over the stage or audience, whereas movers can spot colors at exact points around the performance area.
posted by nevercalm at 1:36 PM on August 14, 2010

They needn't necessarily be LEDs. Intelligent lights, like this, usually have the lamp on all the time, then in front of that are shutters [make it dimmer or 'off' or strobe], colour wheels, gobo [that change the beam shape] wheels.

Because the wheels don't need to move much, less than an inch between colours, the light can change colour quickly. The idea is the same as you describe on older lights, but on a smaller, faster scale.

Some have 3 colour wheels, which mean you can choose the amount of cyan, yellow, magenta, that gets through, so you can make any colour you like.

It's difficult to identify the specific fixture in your photo, here's the wikipedia article on Intelegent lighting. A typical one could be Robe 1200, or others by them, or Martin etc.
posted by kg at 1:45 PM on August 14, 2010

There are a couple different ways this can be done:

- A series of gels on a roll as you describe. Advantages are that it's fairly easy to customize the set of colors, low cost, and usually the scroller only requires one DMX channel to control*. Disadvantages are that you're limited to a discrete set of colors, the audience sees the bump in color if you change while the light is on, long scroll times to change colors, and the gels wear out relatively quickly.

- Replace the gels with small discs of colored glass and mount them on a wheel. This is seen in many mid-range fixtures like the MAC 500 and friends. Advantages are the gels don't burn out, faster scroll time, and you can get a nifty color strobe effect going if you spin the wheel fast. Disadvantages are that you're still limited to a discrete set of colors, except now changing the colors involves disassembling the fixture and buying expensive pieces of dichromatic glass, and the audience still sees a bump in color if you change while the light is on. Often, these types of fixtures will have two color wheels to provide some mixing opportunities.

- Full CMY color mixing. These fixtures have separate colored glass "flags" for cyan, magenta, and yellow mounted in the beam path. Move the flags in and out of the beam and you can make pretty much any color. Advantages are continuously variable color, so you can smoothly shift colors while the light is on and there's no need to preselect a limited set of colors in advance. Disadvantages are cost (though CMY mixing is becoming more and more common), increased space used inside the light for the mechanism, and the need to dedicate 3 channels for color control.

- LEDs. Advantages are low power consumption, great variety of colors and special effects, and long lamp life. Disadvantages are ultra-high cost and lack of control, though this varies a lot; LED intelligent lighting is fairly new tech and there's a huge range between older/cheaper fixtures that give piss-poor color mixing and low brightness and newer/more expensive ones that can be downright amazing.

* DMX is a control protocol used for stage lighting. Each parameter being controlled on an intelligent light (e.g. position, color, intensity, pattern, pattern rotation, frost, focus, prism, etc...) gets at least one channel. Many parameters require additional channels, as position generally needs 2-4 and color up to 3. It's not uncommon for high-end fixtures to use 16+ channels to control their various parameters. Really fancy ones with built in digital video projectors might offer more than 50 channels. Lighting consoles are programmed to vary these channels over time to control the lights. The catch is that the DMX protocol allows only 512 channels per "universe" (basically, per cable), so you're limited to around 24-32 such lights per universe. Fancy lighting consoles can handle 8 or more DMX universes, but many max out at 2, or at least require additional upgrades to output more. Plus you have to run extra cable and distribution for each universe. As such, the number of channels used by various fixtures makes a difference in the overall practicality of the system.
posted by zachlipton at 3:57 PM on August 14, 2010 [2 favorites]

The photo you linked to is Green Day, so here are interviews with the lighting designer and director for their current tour.
posted by Knappster at 5:02 PM on August 14, 2010 [1 favorite]

Finally, a question about something I know the concrete answer to! Oh wait, damn, folks have already answered it. But yeah, what everyone else said about LEDs. And especially what zachlipton said, much more succinctly than I ever would have.

Man I'm kinda shocked (and pleased!) at how many stage lighting folks are on MeFi!
posted by mollymayhem at 6:10 PM on August 14, 2010 [1 favorite]

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