photochromatic interval
interval, photochromatic
Range of low luminances between the absolute threshold of light perception and the threshold of hue. The length of this interval varies with wavelength, being nearly nil around 650 nm (Fig. I15). Syn. achromatic interval. See Purkinje shift; duplicity theory.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann