Because of the growing interest in uniform chromaticity scales, a comparison between the Munsell color space and a color space based on MacAdam’s visual sensitivity data is of importance. In order to make this compar...
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Because of the growing interest in uniform chromaticity scales, a comparison between the Munsell color space and a color space based on MacAdam’s visual sensitivity data is of importance. In order to make this comparison we established the CIE coordinates for a Munsell type cylindrical space sampling conforming to MacAdam’s data. In the color space so formed, a color difference of one-chroma step, for example, will be the same in any region when that difference is calculated from MacAdam’s data. This “MacAdam space” differs materially from Munsell renotation space. The distance of the constant chroma loci from neutral in the purple-blue region is approximately doubled, and the constant hue loci are shifted as much as 10 hue steps in the green and red regions.
This paper is a continuation of RP1209 and describes the cooperative work done by the Association of American Railroads Signal Section, Corning Glass Works, and the National Bureau of Standards, leading to the formula...
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This paper is a continuation of RP1209 and describes the cooperative work done by the Association of American Railroads Signal Section, Corning Glass Works, and the National Bureau of Standards, leading to the formulation of the AAR Signal Section specifications for signal colors and glasses. The previous paper defined the luminous transmission scale used by the signal engineers and glass manufacturers. The present paper describes the glasses selected by these engineers to define the limits of acceptable chromaticities afforded by these glasses when combined with kerosene or electric illuminant. The spectral transmissions of the glasses are given, together with the luminous transmissions and chromaticities for the specified illuminants. The photometric and colorimetric parts of the AAR Signal Section three-part specifications are illustrated, and the reasons given for the choice of tolerances both on the acceptable signal colors and on the glasses certified by the National Bureau of Standards as duplicates of the standard limit glasses. Various other data of interest are given, including the expression of the permissible chromaticities of signal colors in a uniform-chromaticity-scale coordinate system.
The light from high intensity electrodes comes principally from the luminous gas confined within the hemispherical crater of the anode. The distribution of intensity in the beam formed by the source with an accurate p...
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The light from high intensity electrodes comes principally from the luminous gas confined within the hemispherical crater of the anode. The distribution of intensity in the beam formed by the source with an accurate paraboloidal reflector has a marked resemblance to the normal probability curve. This resemblance has been investigated, using all available data of known reliability, and the agreement between curve and test is remarkable. From both theory and test, it is known that the beam formation is influenced by the ratio of the focal length of a mirror to its diameter, and the standard form of mirror has been found to give the best agreement with the probability curve. Also, there is a certain operating latitude allowable in current for given electrodes, and within these limits the intensity curve is relatively unchanged in form. Three sizes of searchlight, 24″, 36″, and 60″ in diameter, have been investigated and all give the same distribution. From these facts, it seems that the probability curve is applicable throughout the range of standard high intensity practice, and with this in mind a test procedure is suggested that may lead to lower testing costs and increased accuracy. Several attempts at a theoretical derivation have failed, and the data are here presented solely as a complete collection of available field tests.
Colorimetric matches between light from objects and a three-primary visual colorimeter are generally metameric, not spectral. The amount of difference between the spectral energy distributions from the object and the ...
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Colorimetric matches between light from objects and a three-primary visual colorimeter are generally metameric, not spectral. The amount of difference between the spectral energy distributions from the object and the calorimeter determines the degree of metamerism. Three indexes of metamerism are considered that depend on this difference. One of these indexes is shown to correlate well with the chromaticity spreads found among observers’ settings for a series of metameric matches. This correlation is independent of luminance. The other indexes do not correlate with the spread of chromaticity of matches by observers.
The latest values for the constants of the black body are used, in conjunction with the Gibson-Tyndall luminous efficiency curve of the spectrum, to compute the luminous efficiency and brightness of the black body ove...
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The latest values for the constants of the black body are used, in conjunction with the Gibson-Tyndall luminous efficiency curve of the spectrum, to compute the luminous efficiency and brightness of the black body over a large range of temperatures. The value.00161 watts per lumen is used for the least mechanical equivalent of light. The computed values agree everywhere to within one per cent with the most recent experimental values.
Experimental data concerning the accuracy of visual chromaticity matching (automatically constant luminance) which were previously summarized graphically, are compared with predictions based on the assumption of a nor...
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Experimental data concerning the accuracy of visual chromaticity matching (automatically constant luminance) which were previously summarized graphically, are compared with predictions based on the assumption of a normal frequency distribution in two dimensions. The standard deviations and correlation coefficient of the two conventional coordinates vary from point to point in the chromaticity diagram and values computed from the experimental data are presented. The major and minor axes, and the angle of inclination of the major axis of the ellipse representing the standard deviation of matchings in any specified direction from any central color, are computed from the parameters of the distribution function, as are the coefficients of the quadratic differential form representing noticeability of chromaticity difference. The conclusions previously published, based on graphical analysis of the data, are confirmed and strengthened by these results, eliminating the former dependence upon personal judgment in construction of ellipses through scattered points.
The International Business Machines Card Programmed Calculator has been wired (by members of the NOTS Mathematics Division) to compute wave functions of several terms of the sharp and diffuse series of potassium (up t...
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The International Business Machines Card Programmed Calculator has been wired (by members of the NOTS Mathematics Division) to compute wave functions of several terms of the sharp and diffuse series of potassium (up to 11 s and 9 d ). Transition probabilities and “oscillator” and “line strengths” estimated from these are reported. The computational procedure employed was that developed by Biermann and Lübeck. Perfect agreement with Biermann and Lübeck was obtained for a check calculation of the 4 p wave function. The reliability of the results is discussed.
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