Abstract

We have plotted several of the 1942 MacAdam ellipses¹ in a normalized constant-luminance cone excitation diagram described by MacLeod and Boynton.² In this diagram the MacAdam data become either circular or ellipse oriented at both 45° and 135°. In contrast, results we presented last year at OSA suggested that a single ellipse oriented at 135° could adequately describe color discrimination data. The simplicity of this result argues strongly for the fundamental nature of the axes in the constant-luminance chromaticity diagram. Further analysis and comparison with the experiments of MacAdam and Boynton and Kambe suggest that the recent data were obtained in conditions that minimize the effects of chromatic adaptation. This analysis suggests that, while a single ellipse may adequately describe color discrimination in some conditions, it may not be descriptive for conditions which produce significant adaptation. This analysis will be discussed with regard to the hypothesis that interactions between two fundamental mechanisms may vary with stimulus conditions and chromatic adaptation.

© 1985 Optical Society of America