Performance Comparison of Various Whiteness Formulas Based on Visual Evaluation Experiments

The Technical Committee TC 1-95 established in the International Commission on Illumination (CIE) is currently active in improving the CIE whiteness formula to extend the scope of the applicability of lighting conditions other than the standard illuminant D65. However, it is important to examine whether or not the CIE whiteness formula is significantly superior to other whiteness formulas under the standard illuminant D65. In this study, we conducted comparisons of the predictive performance of 19 whiteness formulas, including the CIE whiteness formula. These comparisons were based on the results of nine visual evaluation experiments that were conducted by four research groups. The results of the analysis clearly demonstrated that, compared to the CIE whiteness formula, the Uchida and Grum whiteness formulas had better outcomes. The predictive performance of the CIE whiteness formula was ranked 11th among the 19 whiteness formulas. This low predictive performance is due to the structure of the CIE whiteness formula, which does not have a penalty term. We also found that the structure of the Grum whiteness formula was simpler and had better predictive performance than the Uchida whiteness formula. Thus, we conclude that the Grum whiteness formula is superior to the Uchida whiteness formula.