Perceptual Color-Difference Thresholds for Images under Different Viewing Conditions

A psychophysical experiment has been conducted to test the threshold of color difference in displayed images under different viewing conditions. Four ISO SCID 400 images N2, N3, N5 and N7 were used as test images, whose colors were altered in lightness, chroma and hue attributes systematically to form the test image pairs with the original ones. The average color difference in all image pairs ranged from 0.00 to 4.18 CIELAB units. The test image pairs were displayed on a carefully calibrated EIZO CG19 LCD color monitor either in ascending or descending order according to the CIELAB color differences. The test image pairs were assessed by a pass/fail method under D50 and D65 simulators and the illuminance levels were controlled in 5 grades ranging from about 200 lx to 3000 lx. Fourteen normal color vision observers took part in the experiment. The mean colordifference threshold under all conditions were from 0.44 to 1.04 with average threshold of 0.90, 1.00, and 0.51 ΔE*ab for lightness, chroma, and hue difference, respectively. In general, the thresholds under D50 were slightly higher than that under D65 and the lowest threshold under D50 and D65 appeared at about 1500 lx.