Effect of Exposure Duration on Visual Contrast Sensitivity with Square-Wave Gratings*†

Abstract

Contrast sensitivity for square-wave gratings of spatial frequencies between 0.44 and 33.2 cycles/deg was determined for exposure durations between 11 and 500 msec. The space-average luminance of the targets was kept constant at 10 mL, regardless of contrast, and equal to that of the pre- and post-exposure fields, which contained a cross-hair reticle to help maintain accommodation and fixation. At the longest exposure duration (500 msec) the contrast sensitivity function exhibited both the high- and the low-frequency declines described by previous investigators. At the briefest exposure duration tested (11 msec), the low-frequency decline of contrast sensitivity was virtually absent. Log contrast sensitivity improves with increasing exposure duration, but more for high-frequency than for low-frequency gratings. These results are compatible with the assumption that there is a time delay in the occurrence of inhibitory interactions in the retina.