The color rendering tolerances in different bands of the spectrum of an illuminant have been measured by direct experiment using several levels of illumination and a variety of test objects, including pictures, foodstuffs, and the human complexion. The spectral bands were contiguous, covering the whole visible spectrum, and their widths were chosen so that they had approximately equal weight from a color rendering point of view. All tolerances were measured in relation to a full radiator reference illuminant, for single bands and also for combinations of bands. With these results it is possible to predict the color rendering performance of an illuminant knowing only the relative energy distribution in its spectrum. Examples are given. In general, the computed performance agrees with practical judgments derived from ordinary use.
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