Display gamuts usually render complex shapes in a uniform color space, requiring observers to change views to comprehend a 3D plot. We propose a 2D representation of a display color gamut, named "gamut rings," where the area within an arbitrary luminance and hue angle range corresponds to gamut volume. KeywordsHigh dynamic range; wide color gamut; color volume; display gamut size

Historically displays used three colorants in an additive system. During that time, the CIE chromaticity diagram adequately illustrated color capability. Modern displays are not constrained by this additive architecture, and the diagram can fail in its purpose. This is demonstrated by analysis and a large number of display measurements. A device‐independent methodology using CIE 1976 L*a*b* color gamut volume is described that provides a robust means to determine the size of the color gamut. This methodology is then extended to the ‘gamut rings’ diagram as a solution for visualizing color capability that directly correlates to color gamut volume. It is further shown how the methodology can be applied to determine the intersection between two gamut volume boundaries.

In a color matching experiment, the colors of two stimuli might match perfectly to one observer. However, to another, those same two stimuli might not match depending on the spectral characteristics of the two stimuli and each of the observers' visual responses. This phenomenon, that any two observers perceive color matches differently, is termed observer metamerism. Only recently have differences in the factors that affect the spectral response of the human eye been quantified to a degree such that observer metamerism can be realistically modeled over a representative population of human observers. From the statistics of these factors, a large, representative group of such observers-each said to be metameric to a standard-was created in terms of LMS cone spectral responses. Using analysis of variance and error propagation, as suggested by Nimeroff, this sample set was reduced to a complete colorimetric description that includes mean color matching functions along with variance and covariance functions. This simplified representation is then applied to creating arbitrary sets of color matching functions, such as the CIE 1931 and 1964 observers, and their covariance functions to allow the practical characterization of observer-metameric mismatch gamuts for any nominally metameric stimulus pair.

Current HDR display technology approaches the dynamic-range capabilities of the fully adapted human visual system. As such, this technology has potential for performing as a surrogate for real-world scenes in the perceptual evaluation of high-dynamic-range (HDR) image-reproduction algorithms that aim to map HDR scenes to the limited dynamic ranges available in typical display and print technology. Compared with direct image assessment in comparison with real-world scenes, it is clear that use of HDR display technology has the benefit of simplicity in experimental design while maintaining the HDR of the original scene. To evaluate this potential application of HDR display technology, seven published versions of well-known HDR tone-mapping algorithms were benchmarked for perceptual rendering accuracy against each of four real-world scenes constructed in the laboratory and against corresponding images on an HDR display. The results illustrate that visual assessments obtained from the HDR display and those obtained from real-world scenes are in good agreement, validating the potential for HDR display technology as an evaluation tool in this context.

There are claims that multi‐chromatic displays can achieve a wider color gamut by the use of additional highly saturated secondary color channels. However, there are other claims that these displays lose lightness and/or color saturation at brighter levels. These apparently divergent views have led to some controversy in the display industry and at standard setting organizations. This study examines the color gamut volume for a variety of simulated and measured multi‐chromatic (sometimes incorrectly referred to as “multi‐primary”) displays using combinations of white and/or secondary color channels, such as cyan, magenta, and yellow. Furthermore, a two‐dimensional gamut representation, referred to as “gamut rings,” is introduced to illustrate that the addition of nonprimary optical color channels to a trichromatic (RGB) display can result in a significant decrease in the chroma at higher lightness levels. The additional saturated color channels can increase the gamut volume only around their hues at darker levels. The results also confirm the validity of comparing the color light output and white light output for revealing the design trade‐offs between the high‐peak white and the color‐image brightness for multi‐chromatic displays.