CHARACTERIZATION OF SPATIAL ALIASING AND CONTRAST SENSITIVITY IN PERIPHERAL-VISION

Psychometric performance was measured for contrast detection and spati al resolution tasks in foveal and peripheral vision. Objective evidenc e was obtained for a quantitative difference between resolution acuity and detection acuity in the peripheral field. These two types of spat ial acuity differed by up to an order of magnitude (3 vs 30 c/deg at 3 0 deg eccentricity) and they varied with stimulus contrast in distinct ly different ways. Contrast sensitivity at the resolution limit was an order of magnitude above the absolute threshold of unity and the shap e of the contrast sensitivity function was significantly different fro m that measured for foveal vision. The results suggest that current mo dels of eccentricity scaling of contrast sensitivity be re-evaluated t o take account of the extensive aliasing zone of spatial frequencies w hich becomes functional in peripheral vision when the retinal image is well focused.