Standard Practice for Spectrophometry and Description of Color in CIE 1931 System
|Publication Date:||20 September 1966|
This practice is concerned with the spectral characteristics of light-transmitting, diffusing, or reflecting nonluminescent materials: reflectance, transmittance, and color, in the CIE2 system. Measurement of color difference is not of direct concern, but see Gootnote 4. The colors of luminescent (phosphorescent or fluorescent) materials are frequently commercially important enough to require measurement; specialized techniques have been developed for this purpose, but they are beyond the scope of this recommended practice. Due to the frequent occurrence of low levels of fluorescence, and of its effect on measurements, general principles for treating this factor are included. The materials are without limitation as to composition but must be homogeneous to the unaided eye over portions large enough for measurement.
If a test specimen is homogeneous, measurements of portions of it may characterize the material of the specimen; thus, a specimen consisting of an opaque sheet of plastic may be shown to represent adequately this specific material. But if the specimen is such that measurement depends on its geometry (such as thickness) or ir the specimen comprises two or more materials so combined that the measurement depends upon their arrangement, the measurement characterizes not a material but the specimen itself. Thus, a specimen consisting of an incompletely hiding paint film on a ground coat represents not a material, but simply an object made from the superposition of a particular finishing coat on a particular ground coat.
2 Originally recommended in 1931 by the International Commission on Illumination and designated in English speaking countries generally as the ICI system, the system is now designated by the official abbreviation CIE adopted in 1951 from the French name, Commission Internationalede l'Eclairage. The method is applied primarily to spectrophotometry. But its principles are used in visual or photoelectric colorimetry. See Ref. (9) for detailed description. Significant to this practice, the CIE has recently adopted, a supplementary set of color matching functions for use in calculations releated to visual color matching of fields of large angular subtense (more than 4 deg at the eye of the observer). Since the color matches on which this set of color matching functions was based were obtained from observing fields subtending 10 deg at the eye of the observer, these supplementary functions are designed x10,(), y10(), z10(),. These functions are published in the compted Rendue, XIV Session, Brusseles, Belgium, June, 1959, Vol A, p.95; by Judd, D.B. nd Wysecki. G. Color in Business, Science and industry, 2nd Edition, John Wiley and Sons, Inc New York N.Y.1963, Table 27, p 144; by wright W.D. and The Measurement of Colout, 3rd Edition, D. Van Nostrand Co. Inc Princeton N.J 1964 table II p.281