ABSTRACT Psychophysical experiments were conducted to quantify perceived lightness differences between stimuli presented on three background types: a checkerboard pattern, a color‐averaged version of the checkerboard, and a uniform gray background. Color normal observers reported perceived differences between paired stimuli positioned either adjacent or separated by 3° or 8° visual angle. Significant effects of both background type and spatial separation were observed. The gray background produced noticeably smaller perceived lightness differences than either the checkerboard or color‐averaged backgrounds. Moreover, for the gray background, placing the stimuli at a larger distance substantially decreased perceived differences. This gap effect was less pronounced for the checkerboard or color‐averaged backgrounds, likely due to simultaneous contrast effects. The ability of several color difference models to predict the perceptual data was assessed using the Standardized Residual Sum of Squares (STRESS) index. All evaluated models yielded relatively high STRESS values (33.12–45.10, on a scale of 0–100), indicating limited agreement with observer judgments and underscoring the need for improved predictive models for complex visual scenes.
Wu et al. (Fri,) studied this question.