Computation of a <scp> G ₀ </scp> ‐Referenced Lightness Metric Based on <scp>CIE</scp> L*

ABSTRACT Lightness, a critical component of color appearance models, is traditionally computed relative to a diffuse white reference. However, this approach does not fully account for the Helmholtz–Kohlrausch (H–K) effect, where highly saturated colors appear brighter than less saturated ones at the same luminance. To address this limitation, this research proposes a G 0 ‐referenced lightness metric based on CIELAB L*, where G 0 represents the luminance at which a color transitions from a reflective appearance to a self‐luminous one. Defining G 0 as a function of chromaticity using optimal colors as an anchor is aimed at enhancing the accuracy of lightness computations, particularly for colors with high saturation. This research outlines the computational methodology for deriving the G 0 ‐referenced lightness metric, details the challenges involved, and presents results demonstrating the efficacy of this approach across various illuminants and color matching functions.