Chromatic adaptation and color appearance

The contribution of chromatic adaptation to color appearance was established by measuring the perception of achromatic patches under various background conditions. Two main hypotheses were tested. First, that the state of chromatic adaptation is set by the integrated chromaticity over all or part of the scene and, second, that chromatic adaptation is incomplete (i.e. the chromaticity of an apparently achromatic stimulus is not the same as the adapting chromaticity). Experiments measured the effects of various spatial and chromatic background configurations on test stimuli that appear achromatic.

Chromatic adaptation was spectrally incomplete, spatially localized, and slow enough to integrate signals over many typical eye movements. The precision of color constancy under limited conditions was such that chromatic adaptation alone could account for it. The Helson-Judd effect was observed in conjunction with incomplete adaptation. A linear model of chromatic adaptation was modified to take incomplete adaptation levels into account. This model was evaluated using available corresponding colors data and found to make predictions significantly better than more complex models.