Constant hue loci in different color spaces for stimuli in Rec. 2020 color gamut and HDR conditions

Hue is an important attribute for characterizing a color stimulus, which is also an output in various color spaces. The investigations on the hue linearity and constant hue loci for different color spaces were generally conducted using conventional CRT displays or surface color samples, in which the color stimuli were within small color gamuts and viewed under standard dynamic range conditions. With the development of imaging technologies, the hue linearity and constant hue loci need to be investigated for wide color gamuts and high dynamic range conditions, which is critically important for image processing (e.g., gamut mapping and tone mapping). In this study, we carefully carried out a hue matching experiment using high-power LED devices. The color stimuli almost reached Rec. 2020 color gamut with the luminance above the diffuse white luminance (i.e., a high dynamic range condition). The results suggested that the hue linearity of ICTCP color space was the best among the nine color spaces. Twenty-one constant hue loci were derived for each of these nine color spaces, which can be used for hue correction when performing image processing and to further revise the color spaces.