CMY

[Dave W]

Hi,

 

I've looked on Google, wikipedia, the blue room wiki and the blue room itself to find out about CMY colour mixing. I've gathered that by mixing the colours together you can create all (or most) colours and smoothly fade between them. But how does this work in a lighting fixture? I doubt there are three light sources that are independently controlled. Any help would be much appreciated.

 

Cheers

Dave

[mumbles]

Not a stupid question, or at least I don't think so as I couldn't work it out at first.

 

There are 3 wheels, in cyan, yellow and magenta. These each vary in intensity between clear and full c/m/y. As the DMX value for the channel rises, the disc rotates to add the colour to the light. Also, before it confuses, most will also have a seperate wheel that is like a standard wheel with set filters in.

 

Hope this helps.

[LeeStoddart]

Basically... one light source with three graded flags in front of it. Each flag is effectively a filter with a graduation from clear to 100% of a colour Cyan, Magenta or Yellow. By arranging the three flags to be in specific positions you control how much of each filter is in play and that affects the colour which is produced. This is called subtractive mixing.

 

Edit... beaten to it!

 

 

unnecessary quote removed - mods

[Dave W]

oooh, thanks a lot, I'm surprised that wasn't on Google or similar.

[gareth]

Some examples of the kind of graduated-colour glassware used in lighting equipment with CMY colour mixing.

 

The notable exception, of course, is the Varilite VL5 (and other VL wash units that came after it - e.g. VL2416, the new VL500) - rather than using graduated glass, this has three sets of dichroic glass radial 'vanes' (looking a little like the fan blades in the front of a turbofan aircraft engine) which pivot on their own axes. The nature of dichroic glass filters (varying in colour according to the 'angle of incidence') is what makes this technique work.

[paulears]

probably worth noting that this is why it is very difficult to give a proper comparison between DMX values and 'real' gel colours.

 

The differences in how the graduated colours coupled with the optical system combine makes setting absolute values very tricky - the order in which the wheels are fitted and how close together they are also changes things. That said, cmy mixing is still rather neat!

[mumbles]

Agree that if you are trying to use the cmy to match to lee numbers, then it doesn't work well, unless you're lucky with your fixture and the gel number you're trying to match. However, so often I have been using a colour wheel, and being annoyed at the spinning through all the other colour between, where a cmy can just fade from a to b over how ever long you want. This is the main merit of cmy as I see it, and as such it is brilliant.