Color Perception of the Eye

http://hyperphysics.phy-astr.gsu.edu...colcon.html#c1

The Color-Sensitive Cones

In 1965 came experimental confirmation of a long expected result - there are three types of color-sensitive cones in the retina of the human eye, corresponding roughly to red, green, and blue sensitive detectors.

http://hyperphysics.phy-astr.gsu.edu...vis/colcon.gif





Painstaking experiments have yielded response curves for three different kind of cones in the retina of the human eye. The "green" and "red" cones are mostly packed into the fovea centralis. By population, about 64% of the cones are red-sensitive, about 32% green sensitive, and about 2% are blue sensitive. The "blue" cones have the highest sensitivity and are mostly found outside the fovea. The shapes of the curves are obtained by measurement of the absorption by the cones, but the relative heights for the three types are set equal for lack of detailed data. There are fewer blue cones, but the blue sensitivity is comparable to the others, so there must be some boosting mechanism. In the final visual perception, the three types seem to be comparable, but the detailed process of achieving this is not known.

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One interesting thing I have found is that while wearing the glasses on the Procyon if I look downward at about a 45 degree angle or tilt my head backward, my perceptions of blue and purples are greatly increased.
This must have to do with the fact that the blue cones are mostly on the outside of the fovea. Anybody else notice this?