Abstract

The almost-illuminant-independent achromatic variable ξ [J. Opt. Soc. Am A 11, 1003 (1994)] is supplemented by two achromatic variables, both almost illuminant-independent. The results are numerically verified and obtained by means of so-called (human) visual system-response functions, defined as those linear combinations of the color-matching functions that constitute the best possible approximations to δ functions. It is argued that they and not the cone sensitivities are basic to understanding the visual system as a color-constant signal detection system. The three variables solve the color-constancy problem and define a chromatic adaptation transform for blackbody radiators of temperature $T$. The generalization of the results to arbitrary well-behaved illuminants is discussed.

© 1997 Optical Society of America

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