Optimal and acceptable hue ranges for display primaries

For many new displays types (e.g. LCDs, PolyLEDs) the hues of the primaries differ from those of conventional CRTs. In order to identify an optimal and an acceptable range in which these primary hues may vary the following two experiments were performed. In the first experiment observers set the hue (ΔHuv, color rotation about the white point) of either the red, green or blue primary to an optimum for four different (natural) images. In the second experiment the same observers adjusted the hue of each primary separately until they perceived the image as “just acceptable”. The results suggest that the optimal hue of the chromaticities of the red, green and blue primaries may vary about ±4° from the chromaticities set by the EBU (European Broadcast Union). In the acceptance task observers were the least tolerant in accepting a hue variation of the blue primary (±12°) and more tolerant for the green primary (±23°). Results for the red primary were quite asymmetric (+15° for a positive hue and −30° for a negative hue). The results from this study give display manufactures a guideline to test whether the color reproduction of their display is optimal, acceptable or unacceptable.1