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CMY vs. RGB

Discussion in 'Lighting and Electrics' started by gafftaper, Mar 23, 2007.

  1. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Why do they use CMY dichroics in color mixing instruments and not RGB? I'm sure there is a good reason but I'm not sure what it is. The only thing I can think of is that CMY might make better white... am I close at all?
     
  2. Footer

    Footer Senior Team Senior Team Premium Member

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    RGB works great with additive color mixing (multiple sources) and it takes a lot for it to go to white. Subtractive color mixing however works much better with CMY and is less likely to go brown or go black like RGB will.
     
  3. soundlight

    soundlight Well-Known Member

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    RGB mixing also requires three light sources, because it is addative. CMY mixing is nice because it is subractive, so you overlay flags to do it, and this makes it ideal for moving lights.
     
  4. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Duh... Now that makes sense perfect, my brain somehow completely missed that the CMY is subtractive. Hopefully my fund raising is going to pull through and I'll be able to afford some cool CMY toys. Life in the conventional world is so boring.
     
  5. soundlight

    soundlight Well-Known Member

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    SEACHANGER WASH! Such a cool fixture attachment for the S4 body. I think that some of those would be perfect for a blackbox.
     
  6. Van

    Van CBMod CB Mods Premium Member

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    I'd love to be able to use automated fixtures but unfortunatly, in our space it simply isn't doable. Our Grid in the mainstage blackbox is at 14'2" with literally no head room over it, the amount of noise generated by a gobo rotators is almost too much! Someday I hope to get some stuff for our second stage where the grid is an acceptable 16' with 3' of head room over it
     
  7. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Yeah at the top of my list... if I've got money to play with... is a collection of both Seachangers and Seachanger Wash lights. I've played with them at several demos and they are really sweet. Dead silent. Wow what that would do for a light plot.

    Van you should check into the Seachangers, I bet you'll find them quiet enough for your tight space. And they aren't particularly big either. I think they add about 9 inches onto an ellipsoidal. The Wash unit size wise is about like an old Alman or Strand 6X9. The Barbizon guy just did a demo for me here a month ago.

    Also on my dream list of "Toys" are some Seledor LED's... With a 17 foot grid I get a lot of punch out of those 3 Watt LEDs, again Imagine the possibilities.

    My theater came out $800k over budget. So we have to fund raise. The truth is when you bypass the contractor markups I can get WAY more for $400k than was in the the original spec list. I've been lobbying for $700k... "it's cheaper than the lowest bid" right? It also gives me almost $300k for toys. We are trying to sell naming rights which would take care of all my dream toys and set up an endowment for theater equipment upkeep.
     
  8. jfitzpat

    jfitzpat Member

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    Footer4321 and Soundlight hit the biggie, additive vs. subtractive. However, it is actually a surprisingly complex subject. For example, in practice, RGB fixtures and CMY fixtures will not have identical palettes.

    If you are interested, Kurt Nassau has written some technical texts that are (I think) surprisingly readable. For example, THE PHYSICS AND CHEMISTRY OF COLOR: THE FIFTEEN CAUSES OF COLOR is just plain interesting (after you read it, you'll find yourself thinking about the color science of everything you see).

    The 'Bible' in Color is Stiles and Wyszecki's COLOR SCIENCE. But while it is an excellent reference, you certainly wouldn't take it to the beach for a little light reading.

    A bunch of the patents by the Moving fixture and LED fixture companies are also pretty interesting.

    -jjf
     
  9. koncept

    koncept Active Member

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    i was under the impression that instruments like high end's studio spots/washes used a cmy mix but did not use several "color flags" to create the desired color.

    led's on the otherhadn could be an rgb mix correct? since in a par64 for example you could put clusters of rgb and use them all at different intensities to create the desired color.
     
  10. icewolf08

    icewolf08 CBMod CB Mods

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    Most fixtures that have CMY mixing use some system of "flags" to mix the color. Many fixtures with CMY also have a fixed color wheel. The CMY flags are not always flag-like in shape. For instance, in the Martin Mac 600 each color in the CMY has it's own disc. The discs have a toothed (for lack of a better word) pattern of each color on them that goes from a wide spacing to full saturation. Some fixtures have flags that do indeed look like a flag, and "wave" in and out of the path of the light. And some fixtures use pairs of flags to vary the saturation of the color.

    LEDs, as you said, do use RGB to color mix. The basic setup is clusters of LEDs, one in each color, or some pattern (of placement) through the fixture that has each color. We are also starting to see LED fixtures come with a fourth color, amber since that is a particularly hard color to mix via RGB. This type of RGB mixing is similar to the way an LCD TV or computer monitor presents color on the screen. Each pixel in the display contains a red, green, and blue sub-pixel that turn on to varying intensities to produce colors on the screen.
     
  11. jfitzpat

    jfitzpat Member

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    To follow up on Icewolf's comments - look at the Elation PowerSpot thread. In the pictures you will see some quartz substrate disks with triangles of color on them. Each system has its own set of optical issues. For example systems that use varying dichroich saturation have color uniformity issues, designers of paddle and wedge systems have to contend with diffraction and reflection, and so on.

    Although it is slightly off topic, I think that lasers used in larger shows have one of the more interesting coloring systems now. It used to be common to pair up two ion lasers, one argon ('green' and 'blue') with one krypton ('red'). Then use, say, three on/off dichroic filters to give 7 or so colors. Now, you see a lot of mixed gas lasers that look white and have a lot more lines in them. Instead of just a few paddles, a lot of companies now use a modulated crystal. It sort of acts like a high speed, controllable difraction grating.

    -jjf
     

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