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Under the auspices of the ISCC Committee on Color Difference Problems, an experiment was carried out in the visual scaling of small color differences involving six color microspaces. The object‐color samples were visually evaluated by ranking, by subjective estimation, and by acceptability judgments. Visual scales were calculated by traditional procedures. Correlations were calculated between the visual scales and four color‐difference formulas (CIELAB, C1ELUV, FMC‐2, and FCM), and ellipsoids were optimized to the visual data. No fundamental differences were found between the results of the perceptibility judgments and the acceptability judgments. Higher correlations than reported for earlier comparable experiments were obtained between visual and calculated color differences.

In a statistical study of the variability of instrumental color-measurement data, two instruments (a Kollmorgen KCS-40 colorimeter-abridged spectrophotometer and a General Electric Recording Spectrophotometer equipped with a Davidson and Hemmendinger digital tristimulus integrator) provided three modes of measurement. Ten samples were measured 48 times in each mode. Frequency distributions were constructed for several colorimetric quantities, including tristimulus values, chromaticity coordinates, and color differences from the mean. To allow study of the error involved in the measurement of color-difference pairs, three such pairs were included in the ten samples. The beneficial effects of averaging were quantified.

Inc. Col Res Appl, 22, 72-87, 1997 duction of multi-angle measuring spectrophotometers to characterize metallic and pearlescent colors and very Key words: color formulation; radiative transfer theory; powerful personal computers, there is a renewed interest surface corrections; Kubelka-Munk theory in the radiative transfer approach to computer color matching.

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A study of the agreement between a visual assessment and the measurement of the reflectivity of printed metallic inks was performed. A psychophysical property for this percept was identified as visual brilliance. The visual judgments of a series of printed panels were compared with measurements from various types of specular reflectance instruments. The results showed that gloss does not linearly follow the appearance of highly reflective specular surfaces. It was observed that the visual assessment of brilliance was highly correlated to the normalized hemispherical diffuse reflectance factor difference. Further, visual brilliance could be mapped to a logarithmic function of the luminous specular reflectance factor and the measurement scale of log(Y) agreed with the scale of hemispherical diffuse reflectance. It was, thus, concluded that either of these measures may be utilized to establish aims and tolerances for production control of the reproduction of foil-like prints.

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