CIE Method for Calculating Tristimulus Values

Abstract

Abstract Between 1981 and 1983, a working Group of USTC‐1.3 of the CIE prepared new recommendations giving for the first time detailed instructions for the calculation of CIE tristimulus values, for inclusion in Publication CIE No. 15.2, a revision of the CIE document on colorimetry first published in 1971. The new recommendations state that the standard method of performing the integration forming the basic definition of tristimulus values shall be by summation at a wavelength interval of 1 nm over the wavelength ranCe 360–830 nm, but that for most colorimetric purposes the approximation of summation at a 5‐nm interval over the range 380–780 nm should suffice. Recognizing that measured data fulfilling these requirements are not usually available, recommendations were also made concerning abridgement, interpolation, extrapolation, truncation, and the calculation of weighting factors. Although tables of weighting factors were not included in the recommendations to the CIE, they have since been calculated in cooperation with the Working Group and published by the ASTM. This article describes the recommendations, now accepted by the CIE and providing clear and complete guidelines for the uniform calculation of CIE tristimulus values.