Possible evolutionary basis for trichromacy

Roger N. Shepard

doi:10.1117/12.19721

1 August 1990 Possible evolutionary basis for trichromacy

Roger N. Shepard

Proceedings Volume 1250, Perceiving, Measuring, and Using Color; (1990) https://doi.org/10.1117/12.19721
Event: Electronic Imaging: Advanced Devices and Systems, 1990, Santa Clara, CA, United States

Abstract

For normal human observers, color is three-dimensional. The color appearance of any surface can be matched by adjusting just three variables (such as lightness, hue, and saturation). This trichromacy is mediated, but not ultimately explained, by the existence of three classes of photoreceptors -- retinal cones having peak sensitivities to longer, medium, and shorter wavelengths of visible light. Possibly, this trichromacy is the result of a more or less arbitrary compromise between (a) the larger number of dimensions required to represent the full spectral reflectance distributions of surfaces and (b) the smaller number of classes of retinal receptors needed to maintain, through denser retinal packing, higher spatial resolution for each receptor class. Alternatively, building on a linear model for color vision, as formulated by Maloney and Wandell, this paper seeks a less arbitrary basis for trichromacy in the prevailing degrees of freedom of terrestrial illumination. Natural selection may have favored trichromacy because it permits the achievement of color constancy despite terrestrial transformations of sunlight, which, unlike the variations in surface reflectances, have been limited to essentially three degrees of freedom. Any visual system, whether biological or artificial (including a system that requires merely an achromatic, shades-of-gray representation), can achieve constancy of color (and of lightness) only by first analyzing its optical input into three chromatic channels in order to compensate for the prevailing three degrees of freedom of terrestrial illumination.

Citation Download Citation

Roger N. Shepard "Possible evolutionary basis for trichromacy", Proc. SPIE 1250, Perceiving, Measuring, and Using Color, (1 August 1990); https://doi.org/10.1117/12.19721

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available