If a suitable filter is placed in the sample beam of the recording spectrophotometer, the automatic tristimulus integrator may be used for calculations based on illuminants other than Illuminant C without a change in the cams. Instructions for making a filter for use in calculating tristimulus values based on an illuminant approximating Illuminant A are given.
H. R. DAVIDSON, I. H. GODLOVE, J. M. LAMBERT, and G. J. WRIGHT, "An Illuminant-Converting Filter for Use with the Automatic Tristimulus Integrator," J. Opt. Soc. Am. 40, 817-818 (1950)