A luminous efficiency function, VD65* (λ), for daylight adaptation: A correction

We recently proposed a 2 degrees photopic luminosity function, V-D65* (lambda) [J Vis 2005;5:948-968], which improves upon the original CIE 1924 V(lambda) function and its modifications, while being consistent with a linear combination of the Stockman and Sharpe [Vis Res 2000; 40: 1711-1737] long-and middle-wavelength-sensitive cone fundamentals [L(lambda) and M(lambda), respectively]. Its derivation was based on 25-Hz heterochromatic flicker photometric (HFP) data obtained from 40 observers of known genotype on a 1000 troland white (D65) background. However, as a result of an analysis of new luminous efficiency data obtained on an series of chromatic backgrounds [J Vis 2008; 8: 1-26], we now recognize that the 25-Hz flickering targets, though near-flicker-threshold, altered the mean chromaticity of the adapting background. Consequently, we have revised the original analysis, taking into account the changes in mean adapting chromaticity with target wavelength. Our reanalysis of the individual and mean data shows that the V-D65* (k) function for a D65 background should be redefined as 1.89L(lambda) + M(lambda) in quantal terms and as 1.98L(lambda) + M(lambda) in energy terms. The change in the L-cone weighting factor represents a change in luminous efficiency across the spectrum of similar to 0.04 log unit. (C) 2010 Wiley Periodicals, Inc. Col Res Appl, 36, 42-46, 2011; Published online 29 April 2010 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/col.20602