Commonplace viewing and depth discrimination.

Abstract

Measures of commonplace depth discrimination were obtained at observation distances of 200, 750, and 1500 feet in an Arctic area over flat terrain. Comparisons were made with similar measures taken over four different kinds of terrain (including an airstrip) in a desert area and with similar data reported by other investigators.The results indicate that within a range of 100 to 3000 feet the standard deviation (precision) of depth discrimination is related to observation distance (D) approximately as the function, D1.35. Within the same range the associated binocular image disparity decreases approximately as D−0.65. It is suggested that for commonplace viewing the angle of disparity is better conceived of as a measure of relative depth acuity rather than of stereoscopic acuity.The results also suggest that under the conditions studied commonplace depth acuity is 95–100% finer than stereoscopic acuity alone, binocular acuity is only slightly, if at all, superior to monocular acuity, and that the qualities of the terrain such as its texture have little or no effect. It was concluded that stereoscopic vision makes only a slight contribution to the precision of depth discrimination although it may be very important in producing a feeling or effect of depth. The hypothesis was put forth that vernier acuity is the major basis for commonplace depth discrimination.