Abstract

Our ability to see fine detail decreases with reduced luminance. This worsening of visual acuity at low luminance can be attributed to at least three factors: increase in photon noise, change in the optical properties of the eye (increased peripheral optical aberrations and night myopia: Campbell & Green, 1965; Coletta & Clark, 1993) and the shift from cone- to rod-mediated vision, in which resolution capability is poorer (Hecht, 1928; Shlaer, 1937). Another characteristic of vision under low luminance is an increase in the integration period, defined as the duration within which energy from the stimulus can be summed to elicit a visual response. For visual acuity, the integration period has been reported to increase from about 100 ms to about 200 ms as luminance decreases from photopic to scotopic levels (Brown & Black, 1976; Kahneman, 1964).

© 1995 Optical Society of America