Brightness luminous-efficiency functions for point sources and for 2° and 10° fields are based on 6, 63, and 76 subjects, respectively. The function for point sources can be approximated by Judd’s 1951 modification of the CIE <i>V</i>(λ) function. The 2° and 10° functions differ greatly from <i>V</i>(λ). The two functions differ from each other only at wavelengths from 410 through 520 nm, where the differences are attributed to absorption by the macular pigment.
© 1986 Optical Society of America
Mitsuo Ikeda and Yasuhisa Nakano, "Spectral luminous-efficiency functions obtained by direct heterochromatic brightness matching for point sources and for 2° and 10° fields," J. Opt. Soc. Am. A 3, 2105-2108 (1986)