Abstract

We have studied the dynamics of light adaptation by measuring increment thresholds for targets briefly flashed on a spatially uniform background whose luminance is sinusoidally modulated about some mean level. We have found that the increment threshold varies sinusoidally with the relative phase between the flash and background modulation. When expressed as a fraction of the time-averaged threshold, the amplitude of the threshold variation is proportional to the depth of the background modulation and is a low-pass function of the frequency. This function is similar to that describing the frequency dependence of the sinusoidal modulation threshold for a similar target. At all frequencies there is remarkably little phase lag between the background modulation and the resulting variation in an increment-flash threshold.

© 1988 Optical Society of America