Figure 5.

The main finding of our study is that the variability in the UH task is always smaller than in the u*v* task. The ratio between the variability in the UH method and the u*v* method is plotted here against the stimulus luminance level (5, 20, and 50 cd/m²). The intraobserver-variability ratios are in light color, while the interobserver-variability ratios are in dark. Each subplot denotes a separate ambient viewing condition (Dark, D65, and CWF). The calculations for these plots are performed in the u′v′ space, but the same effects are found in other color spaces too.