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 flash duration TB, decreases as luminance L increases: TB = k x L beta , where beta is the duration exponent. The exponent of TB was estimated for 1-deg white flash 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 showed that the duration of the brightest flash TB decreased as L increased with the negative power exponent. Furthermore, the size of the negative exponent decreased as a function of increasing retinal eccentricity. Time-dependent brightness processing in the fovea and periphery is discussed in terms of the psychophysical brightness power function.