Effects of known variations in photopigments on L/M cone ratios estimated from luminous efficiency functions

The extent to which known variations in photopigment λ(max) and optical density may affect cone ratios estimated from the spectral luminous efficiency function (LEF) was examined. LEFs were generated using L- and M-cone fundamentals, one of which had been shifted in λ(max) (± 1, 2, 4 or 6 nm) or varied in peak optical density (increased or decreased by 10, 25 or 50%). A curve-fitting program was then used to estimate the L/M cone ratios for the generated LEFs assuming standard L- and M-cone fundamentals. These modeling exercises indicate that L/M cone ratios estimated from LEFs are highly correlated with long-wave sensitivity and with known variations in L-cone λ(max). Variations in M-cone λ(max) and photopigment optical density for both cone types are also correlated with L/M cone ratios, but have much less impact on the estimated ratios.