Abstract

Foveal contrast thresholds of the light-adapted eye were measured for two point light sources, whose separation could be varied, and for different degrees of out-of-focus imagery. The data for sharp imagery were similar to those obtained by Van den Brink for the dark-adapted eye. It appears that for separations of the point sources from zero to about 3 min of arc the contrast threshold increases linearly. Approximately 3 min of arc (depending upon pupil diameter) is a critical angle of separation, because for greater separations the threshold remains constant. This is interpreted to indicate no overlapping of blur disks, no integration of luminous energy, and no inhibition of the two images for separations greater than this critical angle. Blurring of the images of the points increased the critical angle only slightly. This implies that the distribution of illuminance within the blurred image cannot be predicted from geometrical considerations.

© 1962 Optical Society of America

Peripheral Contrast Thresholds and Blurring of the Retinal Image for a Point Light Source*

Kenneth N. Ogle
J. Opt. Soc. Am. 51(11) 1265-1268 (1961)

Foveal Contrast Thresholds with Blurring of the Retinal Image and Increasing Size of Test Stimulus*

Kenneth N. Ogle
J. Opt. Soc. Am. 51(8) 862-869 (1961)

Blurring of the Retinal Image and Contrast Thresholds in the Fovea*

Kenneth N. Ogle
J. Opt. Soc. Am. 50(4) 307-315 (1960)

Foveal Vision: Dependence of Threshold Energy on the Visual Angle of a Circular Target*

Nelson W. Taylor
J. Opt. Soc. Am. 52(7) 820-825 (1962)

Binocular Summation at the Absolute Threshold of Peripheral Vision*

Leonard Matin
J. Opt. Soc. Am. 52(11) 1276-1286 (1962)