Abstract

Contrast sensitivity increases with grating area. The prime determinants of this spatial integration process are the number and length of grating bars. When grating size is expressed in square cycles (c²) calculated by multiplying grating area A by spatial frequency F squared, spatial integration in foveal vision becomes similar for all spatial frequencies.¹ When the contrast sensitivity data, collected for spatial frequencies of 1.5-3 cycles/deg at the eccentricities of 0-22 deg, were plotted as a function of the number of square cycles, the increase of contrast sensitivity was similar along and across the meridians of the visual field. Also, the increase of contrast sensitivity as a function of grating value (AF²) was at all eccentricities similar along and across the grating bars. The only exception was the grating containing only 1cycle: in that case the increase of contrast sensitivity as a function of bar length was negligible. Although the increase of contrast sensitivity as a function of square cycles was steeper in peripheral than foveal vision, spatial integration saturated at similar grating values irrespective of visual field location. The results indicate that the reduction of contrast sensitivity, produced by dark surround for gratings consisting of a small number of square cycles, is stronger in peripheral than foveal vision, as is the case in lateral masking.

© 1987 Optical Society of America