The standard procedure of calibrating the Donaldson six-primary calorimeter is reviewed critically and some sources of systematic errors which might affect the accuracy of the calibration are discussed In particular, the effect of the temperature variations of the primary filters and the nonuniform spectral transmittances of certain optical components of the instrument are studied. A way is described which leads to an improved calibration accuracy.
G. WYSZECKI and Y. NAYATANI, "Calibration of the Donaldson Colorimeter," J. Opt. Soc. Am. 54, 705-708 (1964)