Abstract

Many researchers assume that the CIE uniform color spaces, CIELUV and CIELAB, can model color contrasts for CRT displays. These color spaces were developed for surface colors, not self-luminous colors as generated on CRTs. CIELUV and CIELAB combine, by vector summation, a luminance component (L^*) and chromaticity components weighted by L^*. The chromaticity components for CIELUV and CIELAB have limited areas of incompatibility when modeling data from self-luminous objects like MacAdam’s ellipses. The luminance component L^*, a function of Y^1/3, is based on the Munsell value function and has not been compared with data from self-luminous objects. We tested the accuracy of L^* and Y^1/3 in modeling the Weber fraction data. Over a typical CRT luminance range, Y^1/3 is adequate while L^* is not. Over an extended luminance range, neither Y^1/3 or L^* model the data. L^* predicts the same number of just noticeable differences for any luminance range. A further problem is that previous psychophysical studies (e.g., MacAdam¹) used vector summation of independent chromatic and luminance contrast components to model color contrasts, an approach not possible with CIELUV and CIELAB since L^* appears in the chromaticity component.

© 1985 Optical Society of America