Asymmetries in the time-course of chromatic adaptation and the significance of contrast

The time-course of chromatic adaptation was determined as a function of the spectral content of the adaptation-light and of image-contrast. The adaptation-lights varied along the chromatic cardinal axes or one of their intermediate axes in an equiluminant plane in colour-space. We found an asymmetry in the initial time-course of adaptation (0.2-10 s) in that adaptation to middle-wavelength light was significantly faster than adaptation to short- and long-wavelength light. The asymmetry was only observed in the presence of a spatially complex pattern. It was fully supported by luminance and chromatic contrast and present under haploscopic stimulus conditions.