Visual acuity as a function of exposure duration*

Abstract

Changes of visual acuity with exposure durations shorter than the critical duration for detection can be attributed to simple light summation; however, changes of visual acuity with longer exposure durations must be otherwise accounted for. This paper shows changes of photopic acuity with prolonged exposure durations, and considers several possible underlying mechanisms. The acuity threshold was found to decrease with exposure durations up to 400 ms and possibly longer. Thus, pupillary and accommodative fluctuations were investigated, as mechanisms concerned, but were found not to have an effect on the phenomenon. A task-specific summation period was sought; however, no evidence for such was found. Also, similar results were found whether the presentation consisted of a single uniform exposure or two discrete exposures with some interval between.