This research compares two psychophysical methods, the method of constant stimuli and the gray scale comparison method. Three color centers were chosen: Red(L*=47.4, a*=61.90, b*=49.5), Green(L*=65.00, a*=-67.6, b*=54.60), and Gray(L*=60, a*=0.00, b*=0,00). Each color center varied in three different directions, L*, C*, and H*. Ten color difference samples were chosen for each color center in each direction, for a total of 30 different samples for the red and green color centers and 10 samples for the gray color center. Each method employed the same three color centers. The sample paris were compared with a neutral anchor pair stimulus of 1.0 ?Eab*. In total there are 70 different color difference samples in each comparison method. 30 observers participated in the experiment where in each experiment they compared 70 different color difference samples in each experiment for a total of 140 observations. The entire experiment consisted of a total of 4,200 observations. The statistical method of probit analysis was utilized to determine results for the method of constant stimuli. Reuslts from the gray scale comparison method were analyzed using a polynomial equation fit to the gray scale differences. The differences between the results of the two methods are due to differences soley in the two psychophysical techniques since the stimuli were identical in both experiments. These differences may in part explain discrepencies found between laboratories emplying the different techniques. David C. Wilbur is currently a semior at the Rochester Institute of Technology. His major field of study is in the Imaging Science with a concentration in Color Science. His research interests include, application of color theory in the industrial environment, printing, and color management techniques.
Wilbur, David, "Color tolerance: A comparison of the method of constant stimuli and the gray scale comaprison method on a CRT" (2000). Thesis. Rochester Institute of Technology. Accessed from
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