LUMINOUS EFFICIENCY, CONE FUNDAMENTALS AND CHROMATIC ADAPTATION

摘要

The photopic luminous efficiency function, V(λ), is by definition fixed in spectral shape. Yet, it is well known that the spectral characteristics of measured luminous efficiency functions can change markedly with chromatic adaptation. Recently, Stockman, Jagle, Pirzer & Sharpe [1] investigated these changes by measuring 25-Hz heterochromatic flicker photometry (HFP) matches in six genotyped male observers on 21 different 1 000 phot, td adapting fields: 14 spectral ones ranging from 430 nm 670 nm; and 7 bichromatic mixtures of 478 nm and 577 nm that varied in the luminance ratio of the two components. They analyzed each function in terms of the best-fitting linear combination of the long- (L) and middle- (M) wavelength sensitive cone fundamentals of Stockman & Sharpe [2]. Taking into account the effects of both the backgrounds and the targets on the mean adapting chromaticity, they found that luminous efficiency on backgrounds between 603 nm and 535 nm could be predicted by a simple model in which the relative L- and M-cone weights are inversely proportional to the mean cone excitations produced in each cone type by the backgrounds and targets, multiplied by a single factor that was roughly independent of background wavelength (and may reflect relative L:M-cone numerosity in the observer). On backgrounds shorter than 535 nm, the changes are consistent with a loss of M-cone sensitivity in excess of the proportionality prediction. A descriptive model of luminous efficiency both for the individual and for the mean standard observer is proposed.