Abstract

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.

© 1959 Optical Society of America

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References

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  1. B. H. Crawford, Farbe 4, 168 (1955).
  2. B. H. Crawford, “The physiology and psychology of colour rendering,” Symposium on Visual Problems of Colour (National Physical Laboratory, Teddington, Middlesex, 1957).

1955 (1)

B. H. Crawford, Farbe 4, 168 (1955).

Crawford, B. H.

B. H. Crawford, Farbe 4, 168 (1955).

B. H. Crawford, “The physiology and psychology of colour rendering,” Symposium on Visual Problems of Colour (National Physical Laboratory, Teddington, Middlesex, 1957).

Farbe (1)

B. H. Crawford, Farbe 4, 168 (1955).

Other (1)

B. H. Crawford, “The physiology and psychology of colour rendering,” Symposium on Visual Problems of Colour (National Physical Laboratory, Teddington, Middlesex, 1957).

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Figures (8)

F. 1
F. 1

Plan of double monochromator system for use as observing telescope in color rendering experiments. 0, illuminated test object; L1, L2, Galilean telescope of unit power for focusing 0 in median plane of P1; M2, plane mirror; M1 concave mirror functioning as collimator and telescope mirror for both halves of the double monochromator, also as field lens focusing the median plane of P1 upon itself at the second passage of light through the system; P1, dispersing and recombining prism, Littrow type; P2, roof prism at which the central spectrum is formed and the light is reflected back in a lower plane so as to pass over the mirror M2 and so out at the exit slit, S1; Sc, screen against stray light; T, observing telescope to give increased angular field of view. The template shutters for modifying the spectral composition of the light are inserted just in front of P2.

F. 2
F. 2

Relation between color-rendering tolerance (single band) and wavelength for one observer.

F. 3
F. 3

Relation between color-rendering tolerance (single band) and wavelength for a number of observers.

F. 4
F. 4

Color-rendering tolerances for single bands for a variety of special objects. Mean for three observers.

F. 5
F. 5

Color-rendering tolerances for single bands for a picture of scenery excuted in artists pastels. Mean for forty observers.

F. 6
F. 6

Effect of age of observer. The results for the observers of Fig. 5 divided into four groups according to age.

F. 7
F. 7

Statistical variation between observers plotted for separate spectral bands.

F. 8
F. 8

Graphical assessment of the color-rendering properties of lamps; fluorescent lamps of various types.

Tables (8)

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Table I Experimentally measured color-rendering tolerances for one observer and a number of pictures and luminance levels.a

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Table II Experimentally measured color-rendering tolerances for several observers and a number of pictures and luminance levels.a

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Table III Experimentally measured color-rendering tolerances for 40 observers and one picture and luminance level.

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Table IV Color-rendering tolerances for complementary spectral bands subtracted singly and in combination.

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Table V Color-rendering tolerances for contiguous spectral bands subtracted singly and in pairs.

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Table VI Ratios of color-rendering tolerances for special and general test objects.

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Table VII Deduced color-rendering tolerances for application in assessment of lamp performance.

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Table VIII Asesssments of color-rendering performance of various types of fluorescent lamp.

Equations (2)

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