Appearance of steadily viewed lights

An interocular matching technique was used to investigate the variation of chromaticity and brightness following steady viewing of a chromatic test light (identical adapting and testing color). Adaptation times were of sufficient duration to ensure stable matches. Following chromatic adaptation we found changes in hue, saturation and brightness. The spectral colors appeared desaturated. The hue shift for the spectral region 546 to 570 nm was towards green and for 586 to 670 nm was towards red. The brightness decrease, independent of chromaticity, was 0.8 log unit at 150 td and 0.3 log unit at 8 td. Data were analyzed within a two-process framework of brightness. Bezold-Brücke effect measurements showed chromaticity shifts in the same direction as for dimming caused by continuous adaptation. Changes in saturation were also observed but were usually in the opposite direction from those found for adaptation.