It has long been clear that the CIE 1924 V(λ) function (CIE, 1926) that was used to construct the CIE 1931 2-deg CMFs (CIE, 1931) seriously underestimates sensitivity at wavelengths below 460 nm. Judd (1951) proposed a revised version of V(λ) to overcome this problem, and derived a new set of CMFs. Yet, like the CIE 1931 CMFs, the Judd-modified functions are reconstructed using the V(λ) function.
From Table 1(5.5.2) of Wyszecki and Stiles (1982).
CIE. (1926). Commission Internationale de l’Éclairage Proceedings, 1924. Cambridge: Cambridge University Press.
CIE. (1932). Commission Internationale de l’Éclairage Proceedings, 1931. Cambridge: Cambridge University Press.
Judd, D. B. (1951). Report of U.S. Secretariat Committee on Colorimetry and Artificial Daylight. In Proceedings of the Twelfth Session of the CIE, Stockholm (vol. 1, pp. 11). Paris: Bureau Central de la CIE.
Stiles, W. S., & Burch, J. M. (1955). Interim report to the Commission Internationale de l’Éclairage Zurich, 1955, on the National Physical Laboratory's investigation of colour-matching. Optica Acta, 2, 168-181.
Vos, J. J. (1978). Colorimetric and photometric properties of a 2-deg fundamental observer. Color Research and Application, 3, 125-128.
Wyszecki, G., & Stiles, W. S. (1982). Color Science: concepts and methods, quantitative data and formulae. (2nd ed.). New York: Wiley.