From Wyszecki & Stiles (1982), Table I(4.3.2).
The standard scotopic luminosity function or V'(l), which was adopted by the CIE in 1951 (CIE, 1951), is based on measurements by Wald (1945) and by Crawford (1949), and is considered to represent observers under the age of 30. The two sets of measurements were made under very different conditions. Wald's data, which are slightly steeper at longer wavelengths, are thresholds for a small 1° diameter target, whereas Crawford's are for a match between two 20° half fields. There is some concern that Crawford's measurements were subject to cone intrusion at long wavelengths.
Crawford (1949) The scotopic visibility function, Proceedings of the Physical Society, B62, 321-334.
CIE Proceedings (1951), Vol. 1, Sec 4; Vol 3, p. 37, Bureau Central de la CIE, Paris, 1951.
Wald, G. (1945). Human vision and the spectrum. Science, 101, 653-658.
Wyszecki, G., & Stiles, W. S. (1982). Color Science: concepts and methods, quantitative data and formulae. (2nd ed.). New York: Wiley.
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