COMPARISON OF SPECTRAL SENSITIVITY USING HETEROCHROMATIC FLICKER PHOTOMETRY AND AN ACUITY CRITERION

The CIE luminosity function V(lambda) is based largely upon the spectral sensitivity of normal observers measured by flicker photometry. Nonetheless, it is used to specify illumination for visual tasks in which the performance criterion is not temporal resolution, e.g., acuity tasks. It has recently become clear that different channels in the human visual system detect acuity targets than detect flicker. Furthermore, the flicker and acuity channels have ostensibly different spectral sensitivities. Thus it becomes important to verify that lights equated by a flicker criterion and lights equated by an acuity criterion agree. If the spectral sensitivity measured by flicker and acuity criteria differ, then performance on an acuity task for lights of equal luminance but dissimilar spectral composition will differ. Six monochromatic background fields (460, 500, 550, 580, 600, and 660 nm) were flicker-matched to a standard white field. The monochromatic-plus-white-standard fields were used as backgrounds for 10 cycle/degree monochromatic gratings presented as increments. Four observers participated in the experiment. Excepting the 460 nm condition, the contrast required to detect a grating on flicker-matched backgrounds is independent of wavelength. Although subserved by different channels, flicker photometric and threshold acuity criteria produce similar spectral sensitivities.