Fundamental problems in color vision. II. Hue, lightness, and saturation of selective samples in chromatic illumination.

Abstract

Selective (chromatic) samples were observed in homogeneous and near-homogeneous illuminants on different backgrounds. Hue, lightness, and saturation depend fully as much upon background as upon composition of source and reflectance of the object. Selective samples have greater constancy of hue than non-selective. Effects of chromatic illuminants depend upon distance of the illuminant point from the white point in the color mixture diagram. The principle of adaptation level as the crucial reference point in determining color conversion is again verified with selective samples and the theory of conversion formulated for non-selective samples is shown to hold for selective samples. The formula for adaptation lightness adequate for non-selective samples yields values too high for selective samples and so a geometric mean of background and sample reflectances was tried with unit wt. for each, which yields results in better agreement with observations reported in this study. The possibility of application of the classical Young-Helmholtz theory, with certain modifications, is pointed out and shown to be compatible with the chief findings of the present work.