TIME-COURSE OF CHROMATIC ADAPTATION FOR COLOR-APPEARANCE JUDGMENTS

Observer production of achromatic appearance has previously been used to measure the time course of chromatic adaptation for changes from da ylight to incandescent illuminants at constant luminance, indicating a n exponential decay of chromatic adaptation with a time constant of th e order of 10 s. The work extends previous results in several ways. Th e psychophysical technique was significantly improved to provide more reliable estimates of color appearance as a function of adaptation dur ation, and the time course of chromatic adaptation was measured for si x chromaticity changes. Three observers tracked achromatic appearance on a computer-controlled CRT display during transitions of 2-min durat ion between the various chromaticities. The results indicate that obse rver differences are statistically significant. However, differences i n time course for different chromaticity changes are not statistically significant (within observer). Single or piecewise exponential decay functions cannot be fitted to the data. However, sum-of-two-exponentia ls functions provided accurate descriptions of the data. The results s uggest two stages of adaptation: one extremely rapid (a few seconds) a nd the other somewhat slower (approximately 1 min). Chromatic adaptati on at constant luminance was 90% complete after approximately 60 s.