[NPPF] Canto Three: The English stuff.. hueshade

[Glenn Scheper]

> Theoretically all hues can be mixed from three basic hues,
> known as primaries.

I have some handle on color technology to go further afield.
When I first started in it, I wondered, "How does a green
photon mix with a red photon, to make a yellow photon?
I don't remember they ever discussed it in physics class.

It turns out the 3-color thing has to do with the eye: Not
to receive a yellow photon; rather a great swarm of photons
with some spectral distribution, that we see as yellow.

The response of all three types of cones in the eye is similar,
a big hump across the spectrum, but the shape of that response
curve is slightly different in the three cone types. It's the
differences in these 3 channels' output that yield color to us.

This appears to make all colors fit in a three-variable space.

Three-color printing is a trompe l'oeil that is only perfect
under certain illuminant conditions, to a standard observer,
which is some amalgam of seventeen people measured years ago.

I was once sent to some conference on color correction, and,
still knowing nothing, spoke up, asking, "Has anyone thought
of using four colors?" After a brief silence, the conference
discussion went forward as if I had never spoken at all.
 
Yours truly,
Glenn Scheper
http://home.earthlink.net/~glenn_scheper/
glenn_scheper + at + earthlink.net
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