Uniform Chromaticity Scales - New Experimental Data

Measurement of the relationship between perceived and computed color differences

Using simulated data sets, we have analyzed some mathematical properties of different statistical measurements that have been employed in previous literature to test the performance of different color-difference formulas. Specifically, the properties of the combined index PF/3 (performance factor obtained as average of three terms), widely employed in current literature, have been considered. A new index named standardized residual sum of squares (STRESS), employed in multidimensional scaling techniques, is recommended. The main difference between PF/3 and STRESS is that the latter is simpler and allows inferences on the statistical significance of two color-difference formulas with respect to a given set of visual data.

Chromaticity-discrimination thresholds with aperture and object colors: experimental results and predictions of some recent color-difference formulas

Threshold-discrimination ellipses were obtained by three normal observers, at five color centers, by the use of two experimental devices, which provided light-surface colors, and the same method and experimental conditions. The ellipses obtained for each center in both devices were quite similar when the sample distributions were appropriate and slightly smaller for object color than for aperture color. The ellipses predicted by three recent color-difference formulas based on the CIE uniform color space (CIELAB) were compared with those experimentally obtained by us as well as by other researchers who analyzed a greater number of color centers. The color-difference formula proposed by the CIE Technical Committee 1-29 [Color Res. Appl. 18, 137 (1993)] provides the best prediction of the semiaxis relationship for all the experimental datasets used, confirming their good performance in previous works [Appl. Opt. 33, 8069 (1993)], although the differences with respect to the experimental results are higher than those attributable to the interobserver variability.

Uniformity of some recent color metrics tested with an accurate color-difference tolerance dataset

The Rochester Institute of Technology-Dupont dataset [Color Res. Appl. 16, 297-316 (1991)] has been used to analyze the uniformity of seven color metrics, developed after CIELUV and CIELAB, with methods similar to those previously applied to several other classical datasets [J. Opt. Soc. Am. A 9, 1247-1253 (1992)]. Significant performance improvements over CIELAB were found with several CIELAB-based metrics, mainly with the model recently proposed by Commission Internationale de L'Eclairage Technical Committee 1-29 [Color Res. Appl. 18, 137-139 (1993)]. Several significant differences found between some pairs of metrics became insignificant when we selected from the Rochester Institute of Technology-Dupont dataset pairs of samples with only chromaticity differences.