The Spectral Chromaticity Coordinates for One British and Eight Egyptian Trichromats*

The spectral chromaticity coordinates have been measured at intervals of 0.01μ between 0.41μ and 0.70μ by means of Wright’s colorimeter for one British observer and for eight Egyptian observers with normal color vision. The matching stimuli were spectral radiations of wavelengths 0.65μ, 0.53μ, and 0.46μ. The units were based on spectral lines 0.5825μ a and 0.494μ (Wright’s system) to eliminate the effect of the yellow ocular pigmentation. Individual differences were noticed which were too large to be accounted for by experimental errors and may be due to differences in the visual mechanisms. The student t test was applied to examine the significance of the differences between the means of the coordinates of the Egyptian group and 4 British observers. No significant difference was found between the means of the red coordinates, but a highly significant difference was noticed in the blue and green coordinates. It was also noticed that the difference was in such a direction that the green was higher and the blue lower in the Egyptians than in the British. Comparison has also been made between the average Egyptian data with those of Wright, Guild, and Weaver; Abney; and the C.I.E. after the transformation of their data to Wright’s system.