SHARPNESS OVERCONSTANCY IN PERIPHERAL-VISION

Although much has been learned about the spatial sampling and filterin g properties of peripheral vision, little attention has been paid to t he remarkably clear appearance of the peripheral visual field, To stud y the apparent sharpness of stimuli presented in the periphery, we pre sented Gaussian blurred horizontal edges at 8.3, 16.6, 24, 32, and 40 deg eccentricity. Observers adjusted the sharpness of a similar edge, viewed foveally, to match the appearance of the peripheral stimulus, A ll observers matched blurred peripheral stimuli with sharper foveal st imuli, We have called this effect ''sharpness overconstancy''. For fie ld sizes of 4 deg, there was greater overconstancy at larger eccentric ities. Scaling the field size of the peripheral stimuli by a cortical magnification factor produced sharpness overconstancy which was indepe ndent of eccentricity. In both cases, there was a slight sharpness und erconstancy for peripherally presented edges blurred only slightly, We consider various explanations of peripheral sharpness overconstancy. (C) 1997 Elsevier Science Ltd.