Unique hue judgments using saturated and desaturated Munsell samples under different light sources

Past studies investigating the unique hues only used samples with a relatively high saturation levels under standard illuminants. In this study, 10 observers selected the four samples with unique hues from 40 V6C8 (Value 6 Chroma 8) and 40 V8C4 (Value 8 Chroma 4) Munsell samples under six light sources, comprising three levels of D-uv (i.e., 0, -0.02, and -0.04) and two levels of correlated color temperature (i.e., 2700 and 3500K). Significant differences were found between the two chroma levels for unique blue and yellow, with the hue angles of unique yellow and blue judged using the desaturated samples being significantly different from those defined in CIECAM02. The iso-lines of unique yellow, blue, and green did not always go through the origin of the a*-b* or a-b planes in CIELAB and CAM02-UCS. Thus, the problems of CIECAM02, CIELAB, and CAM02-UCS identified in this study need further investigations.