Analysis of color volume of multi‐chromatic displays using gamut rings

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. This study examines color gamut volume from a variety of simulated and measured trichromatic (RGB) and multi‐chromatic (sometimes incorrectly referred to as “multi‐primary”) displays. The gamut ring framework illustrates that the addition of nonprimary optical color channels to a trichromatic display can result in a significant decrease in the chroma at higher lightness levels. Comparing the color light output (CLO) and white light output (WLO) reveals the design trade‐offs between the high‐peak white and the color‐image brightness for multi‐chromatic displays.