Abstract

The eye can discount some features of an illuminant substitution but not others. Sorting out which features are discounted helps to organize constancy data, while avoiding possible overstatement of what the visual system can do. In outline form: (1) The eye cannot undo a breakdown of metamerism. (2) The eye discounts illuminant effects on object luminance well, whether (a) the light changes in intensity only, or (b) it changes in color as well. (3) The eye tends to discount the color of the illuminant, but (a) blue-yellow shifts are discounted better than (b) red-green shifts.¹ (4) The eye tends not to discount illuminant effects on color contrast as quantified by (a) the red-green contrast parameter $\widehat{t}$or (b) the blue-yellow contrast parameter $\widehat{d}$.² The poster reviews supporting data.

© 1985 Optical Society of America