PNNL

Abstract

This article examines how the color sample set, color space, and other calculation elements influence the quantification of gamut area. The IES TM-30-18 Gamut Index (Rg) serves as a baseline, with comparisons made to several other measures documented in scientific literature and 12 new measures formulated for this analysis using various components of existing measures. The results indicate that changes in the color sample set, color space, and calculation procedure can all lead to substantial differences in performance characterization. However, it is impossible to determine the relative “accuracy” of any given measure, because gamut area is not directly correlated with any subjective evaluation of color quality. Nonetheless, the utility of different approaches can be weighed based on the merits of individual components of the gamut area calculation and based on the ability of a measure to provide useful information within a complete system for evaluating color rendition. Foremost, the components of a measure of gamut area must be compatible with the needs of other measures of color rendition, so that effective comprehensive models can be established, allowing for tradeoffs between different characteristics to meet application demands. For gamut area measures specifically, it is important to have a reasonably uniform distribution of color samples across hue angle with sufficient quantity to ensure robustness but enough difference to avoid incidents of the hue-angle-order of the samples varying between the test and reference condition. This can also be achieved with larger sample sets by deriving average conditions within hue-angle bins.