EXPONENT OF THE BROCA-SULZER FLASH DURATION AS A FUNCTION OF RETINAL ECCENTRICITY

The flash duration producing maximum brightness-enhancement changes as a power function of luminance, that is, the time locus of the Broca-Sulzer duration T//B, decreases as luminance L increases: T//B equals k multiplied by L** beta , where beta is the duration exponent. The exponent of T//B was estimated for 1-deg white flash with five luminance levels covering the range 3. 94-1. 94 log cd/m**2 in steps if 0. 5 log unit. The retinal loci tested were fovea, 10-, 20-, 30-, 40-, 50-, and 60-deg temporal eccentricities of the dark-adapted human right eye. The following method of brightness maximization was used: the observer adjusted the duration of constant luminance flashes to produce a maximally bright flash. Duration was adjusted by rotating a microprocessor-based potentiometer. The results indicate that the duration of the brightest flash T//B decreased as L increased with the negative power exponent.