Absolute thresholds for moving point sources.

Abstract

The theoretical treatment of absolute and contrast thresholds for moving point sources is presented. The thresholds are tested as functions of the velocity v and observation time t on the assumption that, under all conditions for minimum perceptibility, p quanta must be effectively absorbed in the retina within τ seconds the δ minutes of arc; within τ and δ the integrate capacity in time and space of the sense organ is complete. p, δ, and τ depend on the particular condition of colors of the light used, state of adaptation, place of the retina, and the like.For absolute thresholds in the dark-adapted eye, p=2 quanta independently of the color of the test stimulus. The behavior of experimental data for absolute thresholds of green and red moving point sources is also in agreement with the dependences deduced from theory when p=2. The data were obtained at retinal positions 7° nasal to the fovea in the dark-adapted right eye.