The Size of Acceptable Color Differences

In order to determine the size of acceptable color differences for a particular production problem, about 12 000 individual judgements of the acceptability of 287 samples as matches with 19 standards were made. The samples represented colors in all sections of the color domain, and the samples represented various size color differences from the standards. Colorimetric measurements of the samples were made and the color differences were calculated according to the several methods currently in use. Color differences were then plotted against the visual judgements of acceptability. Calculations based on rather small modifications of the MacAdam ellipses were found to correlate with the visual results much better than do those based on other methods. We found that color differences falling within an ellipsoid about 212 times the size of those published by MacAdam with a radius vector of about 0.15 Munsell value unit parallel to the Y axis were accepted in 50 percent of the observations.