Impact of Color Matching Primaries on Observer Matching: Part II – Observer Variability

In this study, the observer variability in a 10° achromatic color matching experiment using systematically different primaries under immersive, perceptually neutral (4673 K) and stable adapted viewing conditions have been investigated for four different sets of CIE color matching functions (CMFs). The matching reference was illuminated by a spectrally broadband light source at 70 cd/m2 and 4613 K. Fifty-four observers varying in age, gender, ethnicity and eye color participated. The results indicate that certain wavelength regions are more sensitive to generate interobserver variability, such as when a short wavelength primary (404 nm) was applied. Furthermore, of the primary sets investigated, that with peak-wavelengths (636–521–447 nm) close to the “typical” RGB-primaries widely known and used in industry had the smallest interobserver variability. In addition to the significant effect of primary set and CMF set, a significant effect of age on matching variability is also found, whereby the change of the blue primary resulted in a substantial difference in dispersion between younger and older observers, likely caused by age-induced yellowing of the lens. Furthermore, different primary sets tend to have a different impact on intra-observer variability than on interobserver variability. Finally, by comparing the observer variability in the current work with previous studies, the CIE standard deviate observer is found to substantially underestimate the interobserver variability, especially for the primary sets containing a 404 nm LED. Our observers also tend to have similar to smaller inter-variability than those reported in literature, possibly due to methodological differences.