Basic Photographic Materials and Processes, 3rd Edition

appendix D

Tristimulus Value and Chromaticity Coordinate Calculations

 

To determine the tristimulus values X, Y, and Z for an object, the spectral power distribution of the illuminant, S_λ, the object's spectral reflectance factor, R_λ, and the CIE standard observer color-matching functions, x_λ, y_λ, and z_λ, are integrated together as follows:

The S, R and either, x, y, and z, are multiplied together at each wavelength sampled. The Δλ represents the wavelength interval that measurements are made at. Although the interval can vary, it is usually 10 or 20 nanometers for objects. The £_λ indicates that the products of multiplications are summed across ...