Abstract

The intensity and the spectral energy distribution within ranges found in natural daylight have a certain effect on the interpretation of pseudo-isochromatic plates. A variation of illumination between 270 and 1000 lx affects color defectives; the error percentage on plate tests decreasing slightly with higher illuminations. This decrease is chiefly found in deuteranomalous subjects. The color temperature of the illumination affects the number of errors made by both normals and color defectives. As the color temperature is increased, the error percentage increases slightly in normals, distinctly in deuteranomalous and less noticeably in deuteranopes. Protanomalous and protanopic subjects do not show a significant effect. On the average, the same percentages of errors result when either a Macbeth easel daylight lamp or a fluorescent daylight lamp is used for the illumination of the plates, provided the same intensity is present.

It is recommended that only artificial daylight of a standardized color temperature and intensity be used to obtain comparable results in pseudo-isochromatic plate tests.

© 1952 Optical Society of America

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