Abstract

To compare the effects of bleaching adaptation and background adaptation on spatial vision, we measured contrast sensitivity functions (CSFs) during dark adaptation and on steady back grounds of various luminances. Measurement of the CSFs during dark adaptation (without adding a steady background) required designing a special stimulus. This stimulus was the sum of a 2-D Gaussian blob (intensity A) and a 2-D Gaussian-damped sinewave (amplitude A) with a bandwidth of 0.5 octaves. To prevent detection from being mediated by the Gaussian blob, the sinewave component was added in either a + or – 45° orientation and the subject had to judge the orientation. Thresholds, for spatial frequencies from 1 to 15 c/deg, were measured following full bleaches and on backgrounds from 0 to 10,000 td. Like earlier studies, we observed the square-root law for high spatial frequencies and Weber’s law for low spatial frequencies. In other words, as background luminance increased, the CSF increased at high spatial frequencies relative to low. In contrast, the shape of the CSF was nearly invariant during dark adaptation.

© 1991 Optical Society of America