On derivation of spectral sensitivities of the human cones from trichromatic colour matching functions

Despite the recent advance made by using the direct methods of retinal densitometry, microspectrophotometry and suction electrophysiology, the psychophysical approach based on colour matching data still remains an important source of accurate information about the spectral sensitivity of the cone photoreceptors in the human visual system. However, the commonly used technique of estimating cone sensitivities, based on the assumption that dichromacy is caused by the lack of one of the three types of the cone photoreceptors, requires the colour matching functions not only from trichromatic observers but from dichromats as well. Here we evaluate an alternative approach, originally put forward by Bongard and Smirnov, that derives cone spectral sensitivities from colour matching functions only; without resorting to colour deficiency or any other data. When applied to CIE standard colour matching functions, this method yields curves of spectral sensitivities that are close to the classical Smith–Pokorny fundamentals, though the long-wave cone is shifted towards the short-wave region of the spectrum by 5 nm, as compared with Smith and Pokorny’s results.