Representing color as multiple independent scales: brightness versus saturation

The concept of color space has served as a basis for vast scientific inquiries into the representation of color, including colorimetry, psychology, and neuroscience. However, the ideal color space that can model color appearance attributes and color difference as a uniform Euclidean space is still, to our best knowledge, not yet available. In this work, based on the alternative representation of independent 1D color scales, the brightness and saturation scales for five Munsell principal hues were collected via partition scaling, where the MacAdam optimal colors served as anchors. Furthermore, the interactions between brightness and saturation were evaluated using maximum likelihood conjoint measurement. For the average observer, saturation as constant chromaticity is independent of luminance changes, while brightness receives a small positive contribution from the physical saturation dimension. This work further supports the feasibility of representing color as multiple independent scales and provides the framework for further investigation of other color attributes.