Effect of Printed Color Sample Separation and Color-Difference Magnitude on Perceived Color Difference

460 pairs of printed samples, around 5 CIE recommended color centers, with/without gap, and 4 color-difference magnitudes of 1, 2, 4 and 8 in CIELAB units, were employed to study the effects of separation and color-difference magnitude on perceived color difference. All the sample pairs were visually evaluated 20 times, using a gray-scale method, by a panel of 15 observers. The experimental results show that the smaller the color difference is, the larger the uncertainty of perceived color difference will be. Comparing datasets gathered with and without separation, it was found that the smaller the color difference is, the more obvious the influence of the gap between two samples will be. The visual data were also used to test the performance of six color-difference equations: CIELAB, CIEDE2000, CIE94, CMC, CAM02-UCS, and CAM16-UCS, the results show that CAM16-UCS outperformed the remained color-difference formulas.