Physiology of Color Perception
Perception of color begins with specialized retinal cells containing pigments with different spectral sensitivities, known as cone cells. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic color vision.
Each individual cone contains pigments composed of opsin apoprotein, which is covalently linked to either 11-cis-hydroretinal or more rarely 11-cis-dehydroretinal.
The cones are conventionally labeled according to the ordering of the wavelengths of the peaks of their spectral sensitivities: short (S), medium (M), and long (L) cone types. These three types do not correspond well to particular colors as we know them. Rather, the perception of color is achieved by a complex process that starts with the differential output of these cells in the retina and it will be finalized in the visual cortex and associative areas of the brain.
For example, while the L cones have been referred to simply as red receptors, microspectrophotometry has shown that their peak sensitivity is in the greenish-yellow region of the spectrum. Similarly, the S- and M-cones do not directly correspond to blue and green, although they are often depicted as such. It is important to note that the RGB color model is merely a convenient means for representing color, and is not directly based on the types of cones in the human eye.
The peak response of human cone cells varies, even among individuals with 'normal' color vision; in some non-human species this polymorphic variation is even greater, and it may well be adaptive.
Read more about this topic: Color Vision
Famous quotes containing the words physiology, color and/or perception:
“The world moves, but we seem to move with it. When I studied physiology before ... there were two hundred and eight bones in the body. Now there are two hundred and thirty- eight.”
—Ellen Henrietta Swallow Richards (1842–1911)
“It is never the thing but the version of the thing:
The fragrance of the woman not her self,
Her self in her manner not the solid block,
The day in its color not perpending time,
Time in its weather, our most sovereign lord,
The weather in words and words in sounds of sound.”
—Wallace Stevens (1879–1955)
“The peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.”
—John Stuart Mill (1806–1873)