Metric of color-space coverage for wide-gamut displays

Abstract

Assessing the coverage of the color space of Recommendation ITU-R BT.2020 (Rec. 2020) has become increasingly important in the design of wide-gamut displays, and an appropriate metric for measuring the display gamut size is urgently needed. Display manufactures calculate the area ratios of their displays' RGB triangles to a standard RGB triangle in the CIE 1931 xy or CIE 1976 u'v' chromaticity diagram to indicate the displays' relative gamut size. However, they typically fail to mention which of the two diagrams the metric is based on. This paper shows that the ratios calculated in the two chromaticity diagrams are highly inconsistent, and that the Rec. 2020 area-coverage ratios for wide-gamut displays in the xy diagram are much more correlated to the Rec. 2020 volume-coverage ratios in some color-appearance spaces than the Rec. 2020 area-coverage ratios in the u'v' diagram. This paper recommends the use of the xy diagram for area-coverage ratio calculations for wide-gamut displays.