Foveal luminance discrimination as a function of the duration of the decrement or increment in luminance.

Abstract

A determination of the minimum luminance [DELTA]I, added or subtracted from an adapting luminance I to obtain difference discrimination over a large range of values of I and for 10 durations of [DELTA]I, showed the function log ([DELTA]I/I) to vary in the same manner as a function of log I (constant value of [DELTA] I) for both increments and decrements of luminance. With constant log I, the log ([DELTA]I/I) values are highest for short durations and decrease with increasing durations to a critical point, thereafter remaining constant. The relation between threshold I and duration t, for constant I, is given by the equation [DELTA]I.t=k for values of t below a critical duration, beyond which the relationship becomes [DELTA]I=Constant.