Factors underlying individual differences in the color matches of normal observers.

We have used a factor analysis of the Stiles-Burch [Opt. Acta 6, 1 (1959)] 10 degrees field color matches to examine the basis of individual differences in the color matches made by observers with normal color vision. The differences in the matches are primarily due to interobserver variations in the macular-pigment density [with a standard deviation (sigma) of 0.12 at 460 nm]; the lens-pigment density (sigma = 0.18 at 400 nm); the spectral position of the long-wavelength-sensitive (sigma = 50.3 cm-1), medium-wavelength sensitive (sigma = 31.9 cm-1), and short-wavelength-sensitive (sigma = 45.3 cm-1) photopigments; the covarying densities of the three photopigments (sigma = 0.045); and the degree of rod intrusion. Variations in the different factors appear to be uncorrelated. Comparable estimates of the sources and range of interobserver differences in color matching were obtained from a similar analysis of the Stiles-Burch 2 degrees color matches [Opt. Acta 2, 168 (1955)].