Saturday, August 16, 2008

Complementary colors

A friend showed me a link to this online applet:

As we all know, two colors are complementary if they cancel each other out, i.e. they produce grey when mixed equally. If you play around with it you’ll notice that if, for example, you enter the RGB code for Anita’s shirt, you’ll see that its RGB complementary color is blue. Obviously, you get the same effect, if you invert the picture in Photoshop (ctrl + i). But, as you may know, complementary colors are different for each basic color model. If you invert the same picture in the CMYK mode, you’ll get completely different complementary colors.

To make sure we are talking about the same thing, I’d like to define how I normally use the term “complementary color”.

When we refer to complementary colors, traditional artists usually think of pairs like red – green, blue – orange, yellow – purple. These are based on the subtractive RYB model of primary colors red, yellow, blue. As you can see in the color wheel, a primary color is opposite to the secondary color mixed by the other two primaries.

This same principle is true for the additive RGB model (red, green, blue):
red vs. cyan
(mix of blue and green)
green vs. magenta
(mix of blue and red)
blue vs. yellow (mix of red and green)

Sometimes red and green (RYB) are called complementary while red and cyan (RGB) are called negative colors. In order to avoid confusion I will adhere to this distinction. (So the wackerart-applet above gives you the negative colors.)

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