Visible persistence: effects of luminance, spatial frequency and orientation.

Square-wave gratings of various space-average luminances, spatial frequencies and orientations were presented briefly to observers, who were asked to adjust a brief visual probe to coincide with the end of the longer-lasting, gradually decaying sensory trace of these stimuli. Visible persistence of 2 and 7 c/deg gratings increased with increasing luminance, and an interaction was found at approx. 6 cd/m2 between luminance and spatial frequency. The persistence curves showed a low-pass frequency characteristic at low mean luminance levels, whereas at high luminances, they presented a band-pass frequency characteristic. Persistence of a 7 c/deg grating was longer at oblique orientations than at horizontal or vertical orientations. These findings were related to properties of transient and sustained channels in human vision.