A new high precision, tristimulus, filter colorimeter suitable both for research and for industrial use has been developed. The instrument can reproducibly measure CIE tristimulus values X, Y, and Z, and ratios of tristimulus values, sample to standard, to four significant figures for most colours. Color differences considerably smaller than those which a trained observer can visually detect can be measured on all colors from whites to blacks of about density 4. The luminous apparent reflectance of carefully polished black glass has been measured as 0.012%. Tables of value functions and alignement charts have been prepared which permit rapid conversion of instrumental measurements into color coordinates or coordinated differences of actual visual spacing in a modified Adams chromatic value system.
