The design and construction of an experimental subjective color comparator is discussed. The unit permits binocular viewing of a constant, 2-degree split matching field with a dark surround. During observation of the field, continuous adjustments of the color of the “standard” side are possible with three controls, each associated with one of the subjective attributes of color. Data useful in calculating the I.C.I. tristimulus values for the matched sample appear on calibrated dials. Color samples to be matched by Illuminant “<i>C</i>” are inserted in the instrument on small cards. Larger samples—external to the comparator—such as textiles, agricultural products, wall panels, etc., can be evaluated for all types of illumination. In every case, texture in the sample is obscured by the comparator mechanism. Some data is presented to indicate the matching tolerances that can be expected.
ELLWOOD J. KING and DONALD S. RODBELL, "An Experimental Color Comparator," J. Opt. Soc. Am. 41, 830-835 (1951)