The best practical test of color vision is the printed polychromatic, typified by the Ishihara. Its flaw is that, being calibrated to a standard illuminant which is required for actual testing, it becomes undependable with deviations from this standard. In practice the standard is rarely provided, because it requires special artificial installations which are rarely available or even appreciated as a necessity. Hence, improper illumination is the rule rather than the exception, and accounts for the passing of 50 percent of color defectives in the Navy, for example. The present report, the first of a projected series, discusses solely the basic technical aspects of a new polychromatic printed test for red-green deficiency which retains stability and diagnostic integrity under a range of illumination far wider than that encountered in testing under natural or artificial sources, from minus-blue to 14,000°K. With this, testing may be done in disregard of composition of illuminant. Thus a source of error is eliminated which has seriously impaired the utility of what is otherwise the most desirable type of practical test.
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