Impact of matching field size on color matching (functions) accuracy

Abstract

AbstractAccurate colorimetry starts with accurate color matching functions (CMFs). Due to changes in the macular pigment and cone pigment optical densities at different retinal locations, different CMFs are required for different stimulus field sizes. To characterize the accuracy of the CIE recommendation for the use of 2° and 10° standard CMFs and the field‐size dependent CIEPO06 model, in this study, a series of achromatic matching experiments were performed with 2°, 4°, 6°, 8°, and 10° bipartite fields using spectrally narrowband primaries. Using the CIEPO06 model, optimal field sizes were estimated that minimize the chromaticity differences between the spectrally narrowband observer matches and the spectrally broadband achromatic target. It was found that the optimal field size estimated using the CIEPO06 model is close to half the actual bipartite field size in most cases, except for the 2° field. The discrepancy between the 10° bipartite field in Stiles & Burch's experiments and our optimal field size (6.54°) was assumed to be due to different individual color comparison strategies. However, the results of experiments requiring specific observer gaze positions did not support this assumption and the reason for the discrepancy remains unclear. Confirming our earlier results, the primary set (636, 521, 447 nm) was again found to be largely insensitive to changes in CMFs and to provide the most accurate matches under various fields of view. The inter‐ and intra‐observer variability ellipses for 2° matches are larger than those for 10°, consistent with Brown's finding for color discrimination ellipses. The magnitude of the intraobserver variability was similar for all field sizes, except for 2° field size, where matching errors were larger for some primary sets.