The proposed 2-deg cone fundamentals are based on the CIE XYZ 1964 10-deg color matching functions.
From Table A of Stockman, MacLeod and Johnson (1993) Journal of the Optical Society of America A, 10, 2491-2521
Columns 2, 3, and 4: logarithms of proposed cone sensitivities based on the , and 10-deg CMFs of the CIE 1964 supplementary standard observer, derived from the following transformations, and adapted for small field application through the corrections described below:
The S-cone sensitivities have been extended at lambda > 520 nm by using the following function:
(where λ is the wavelength in nm).
The 2-deg cone fundamentals in Columns 2, 3 and 4 were calculated using the above equations by (i) converting the above 10-deg cone fundamentals to photopigment optical density spectra by assuming 1.28 times the (open pupil) van Norren & Vos (1974) lens template, 0.28 times the Wyszecki & Stiles macular template, and a peak photopigment optical density of 0.30; and then (ii) converting the action spectra to 2-deg cone fundamentals by assuming the same lens densities, 0.70 times the macular template and a peak photopigment optical density of 0.40 (see text for details). The Wyszecki & Stiles macular template was extended beyond 400 nm by assuming densities of 0.0425 at 395 nm and zero at 390 nm.
The CIE 1964 observer has a slightly higher lens density than the Stiles & Burch (1955) observer. This difference is also apparent in the differences between the two sets of Stockman, MacLeod and Johnson cone fundamentals.
The tabulated M- and L-cone sensitivities can be extended into the infrared, where self-screening is negligible, by using the above linear equations in , and multiplied by wavelength-independent scaling factors of 1.103 for M and 1.102 for L.
All coefficients given above have been scaled so that in energy units the interpolated peak cone sensitivities are equal to 1.
Stiles, W. S. & Burch, J. M. (1955). Interim report to the Commission Internationale de l'Eclairage Zurich, 1955, on the National Physical Laboratory's investigation of colour-matching. Optica Acta, 2, 168-181.
Stiles, W. S. & Burch, J. M. (1959). NPL colour-matching investigation: Final report. Optica Acta, 6, 1-26.
Stockman, MacLeod and Johnson (1993). Isolation of the middle- and long-wavelength sensitive cones in normal trichromats. Journal of the Optical Society of America A, 10, 2491-2521
van Norren, D. & Vos, J. J. (1974). Spectral transmission of the human ocular media. Vision Research, 14, 1237-1244.
Wyszecki, G., & Stiles, W. S. (1982). Color Science: concepts and methods, quantitative data and formulae. (2nd ed.). New York: Wiley.