COLOR APPEARANCE UNDER CHROMATIC ADAPTATION VARIED ALONG THEORETICALLY SIGNIFICANT AXES IN COLOR SPACE

Changes in color appearance caused by chromatic adaptation were measur ed with a wide range of adapting fields. Observers viewed a 39'-55' an nular test field composed of an admixture of lights from the red phosp hor and the green phosphor of a CRT. The annular mixture field was cen tered and superimposed upon a 4.7 degrees steady, circular background field. After the observer was completely adapted to the background, th e luminance of the red phosphor in the test was held fixed while the o bserver adjusted the luminance of the green phosphor until the test ap peared neither reddish nor greenish. Twenty-two equiluminant backgroun ds (4.5 cd/m(2), similar to 50 Td) were systematically selected along two axes in Judd chromaticity space. One axis was along tritanopic con fusion lines, with middle-wavelength-sensitive- (M-) and long-waveleng th-sensitive- (L-) cone stimulation held constant. The other axis main tained constant short-wavelength-sensitive- (S-) cone stimulation. The results show that adapting backgrounds that were varied along tritano pic confusion lines do not have a differential effect on color appeara nce at high test levels (well above the adapting level). At lower test levels there is a systematic change in color appearance of the test l ight, which is quantitatively Along constant S-cone-stimulation lines, adapting backgrounds differentially affect color appearance in a syst ematic way, reflecting changes in receptoral gain and the additive con tribution. The measurements taken with adapting fields throughout colo r space are described by the two-process model of chromatic adaptation .