Sensitivity to modulation of color distribution in multicolored textures

We evaluated the discriminability of color distributions in square-element textures. Each texture contained 225 colors, represented by a distribution of color vectors in color space defined by the L-M and S-(L+M) axes. Each color distribution was systematically manipulated by modulating the distribution of the vector lengths sinusoidally as a function of the direction in the color space. The results showed that it is difficult to resolve a color distribution modulated in more than three cycles per 360 degrees in the chromatic direction. The difference in components along the cardinal axes is not a critical factor in the discrimination of the color distribution. An analysis using a line-element model suggested that the discrimination of the color distribution is mediated by multiple chromatic channels that are tuned to a variety of directions in the color space with a half-height-half-bandwidth of about 40 degrees in the chromatic direction.