Abstract

Adaptation to variations in ambient light level has been studied using both periodic and aperiodic stimuli. Here we focus on several well-documented results. When the mean luminance L of a spatially and/or temporally periodic stimulus is increased, typically log ΔL is first constant and then increases with log L until reaching a slope of 1.0 (Weber's law). The transition luminance (the mean luminance at which the transition from constant ΔL to increasing ΔL occurs) increases with increasing spatial and temporal frequency. As the onset of a brief spatially aperiodic pulse of light is delayed relative to the onset of a spatially aperiodic ambient field, the transition luminance increases and the slope of log ΔL vs log L (above the transition luminance) decreases from very high to 1.0. These results tend to be analyzed within two different theoretical frameworks. Models we reviewed from the periodic literature seem unable to handle the aperiodic results. Similarly models reviewed from the aperiodic literature seem unable to handle the periodic results.

© 1989 Optical Society of America