Color physics and color perception

[danihel]

hi
i've been intrigued by certain "inconsistency" between light frequencies and the way we see them for some time by now.
if you mix red and yellow you get orange, if you mix red and green you get yellow, blue and yellow makes green, blue and green makes cyan. Now in all of these cases by mixing two colors corresponding to two different light frequencies you got pretty much a color corresponding to the light frequency somewhere in the middle.
But if you mix blue and red you'll get violet which is of higher frequency then blue, red being the bottom of visible spectrum. Is there some kind of biological reason why does the visible spectrum create a color wheel in our brain?
I'm not physicist and i don't understand the math of composing waves, could it be that our brain interprets different light frequency compositions as the same one color?

 

[JaredJames]

What do you mean "mix" them?

As I understand it, you can't 'mix' light to gain a new colour. That only works with paints (or any colouring medium).

If you only have blue light and you send it through a red filter, it cancels out virtually all of the light (on an overhead projector you get a black patch where they cover each other).

 

[danihel]

well i don't know but i think if you put dots of those colors close enough together your eye will perceive them as one color as if you mixed them chemically also when you look too long at one color then close your eyes you see the opposite color on the "color wheel" which also points to the way we see as if the colors were enclosed in some kind of loop

 

[Andy Resnick]

hi
i've been intrigued by certain "inconsistency" between light frequencies and the way we see them for some time by now.

Color vision is not entirely understood. Certainly, we know about the different cones and the wavelengths they respond to. But I'm not sure we understand the (perceptual) origin of violet, brown, or pastel hues: those appear to require 'post-processing', as it were.

 

[Drakkith]

If I had to guess, I'd say that either:

A. The individual specks of paint reflect different light. When mixed, the spacing between these are so close that when your eye receives light from the paint, it is a mix of red and blue and happens to look purple. Don't know why.

B. The paint mixes and the new materiel doesn't reflect red and blue anymore, but actually reflects purple light.

The key here is that paint ABSORBS certain frequencies of light. When you mix all the paints together, there isn't any reflected, resulting in a Black color.

On the opposite, white light is a combination of all colors.