In this paper we seek linear combinations of the CIE-1931 Standard Observer tristimulus functions that could plausibly relate to action spectra of organic dyes. It turns out that this simple criterion yields an almost unique determination of the fundamental response functions of the human cone pigments. The results are in good agreement with those obtained by radically different methods. Just because each of the methods of obtaining the fundamental response functions has its own uncertainties and assumptions, it is important to use as many different approaches as possible, and then to interrelate them. Our method shares with the other methods the limitation that the red response function is the least well-determined. The three fundamental response functions determined in this paper are for the 2° (foveal) field and are defined by R(λ)=0.901 x¯(λ)+0.247 y¯(λ)-0.148 z¯(λ), G(λ)=-0.508 x¯(λ)+1.409 y¯(λ)+0.099 z¯(λ), B(λ)=z¯(λ). Certain minor deficiencies in the CIE-1931 color functions are emphasized by our examination. These deficiencies are related to the smoothing of the very real fine structure in the blue region.
GEORGE R . BIRD and R. CLARK JONES, "Estimation of the Spectral Response Functions of the Human Cone Pigments," J. Opt. Soc. Am. 55, 1686-1691 (1965)