Dec. 29th, 2014

milktree: (Brain science)
I've known for years that additive (light) and subtractive (paint) primary colors were different; the former are red, green, and blue; while the latter are red, yellow, and blue.

It never really made any sense to me that red and blue would be the same but green would be swapped with yellow. I assumed it had something to do with the oddities of the way retinas worked or something.

Today I finally got it. I was reading a book about how to draw birds which has a section on color and color mixing.

The problem (the answer?) is that it's *not* red, green, and blue for paints. That's wrong, and has always been wrong. For subtractive color the primaries are cyan, magenta, and yellow. Red and blue are wrong!

This should be obvious if you look at *any color printer ever*, which all use CMYK inks (+K,'cuz black is hard to do simply/practically without it)

The short form is that you *can* mix to get both blue and red (magenta & cyan, and magenta & yellow respectively) and you *can't* mix red, yellow, and blue to get a good green, or thin out red to get pink, and violet is problematic, too. Plus, you know, cyan and magenta are impossible.

However, if you use CMY for paint and RGB for light, then magic happens: The secondary colors for one are the primary colors for the other. When you lay the two wheels out next to each other, it's obvious:

(click for bigger)

The money quote:

    If cyan, magenta, and yellow are the true primary colors for pigment, the relationship with the light color wheel also makes more sense. Televisions and computer monitors mix beams of red, blue, and green light to make all of the colors you see on your screen. The secondary colors that result from mixing light are cyan, magenta, and yellow. The color wheel for light has the same colors as the color wheel for pigment.



I'm sure this is old hat for those of you who actually deal with color with any enthusiasm, but it was a neat "Oh! Neat!" moment for me.

Here are the two pages of the book, if'n you want to you read them. They basically say the same thing as above, but better, and with more words:

page1.jpg
page2.jpg

I took the pictures with a cell phone, in a less than photographically ideally lit room, so they're a little grainy.

Actually, let me rephrase that: Holy shit! I took those perfectly reasonable pictures in a dim room with my *phone*! My fucking *telephone*! I love the future.

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