Color discrimination metric based on cone cell sensitivity.

Abstract

Based on the cone cell sensitivity, a new metric defined as cone sensitivity difference (CSD) was proposed to describe the color discrimination property of a light source. We conducted experiments at mesopic condition to test the performance of the metric. A color temperature tunable poly-chromatic LED system consisted of 7 single-color LEDs was utilized in the experiments. The performance of the metric was assessed by computing the Spearman and Pearson correlation coefficients with the observers' ratings of color discrimination obtained from the experiments. Several conventional color quality metrics, including R_a, color quality scale (Q_a), gamut area scale (Q_g) and color-discrimination index (CDI), were also evaluated with respect to color discrimination by correlation analyses. Among the selected metrics, Q_g had the best Spearman and Pearson correlation coefficients with the observers' ratings for most of the correlated color temperatures (CCTs). The newly proposed CSD was highly (p<0.01) correlated with Q_g, and its correlation with the observers' ratings increased at the higher CCTs. For CCT above 5000K, CSD had significant Pearson correlation coefficients with the observers' ratings. There was a possibility that CSD would be qualified to describe color discrimination with further optimization.