CONTRAST GAIN-CONTROL - A BILINEAR MODEL FOR CHROMATIC SELECTIVITY

We report the results of psychophysical experiments on color contrast induction. In earlier work [Vision Res. 34, 3111 (1994)], we showed th at modulating the spatial contrast of an annulus in time induces an ap parent modulation of-the contrast of a central disk, at isoluminance. Here we vary the chromatic properties of disk and annulus systematical ly in a study of the interactions among the luminance and the color-op ponent channels. Results show that induced contrast depends linearly o n both disk and annulus contrast, at low and moderate contrast levels. This dependence leads us to propose a bilinear model for color contra st gain control. The model predicts the magnitude and the chromatic pr operties of induced contrast. In agreement with experimental results, the model displays chromatic selectivity in contrast gain control and a negligible effect of contrast modulation at isoluminance on the appe arance of achromatic contrast. We show that the bilinear model for chr omatic selectivity may be realized as a feed-forward multiplicative ga in control. Data collected at high contrast levels are fit by embellis hing the model with saturating nonlinearities in the contrast gain con trol of each color channel.