C. S. McCamy’s scientific contributions

Color order systems must be distinguished from colorant order systems and other systematic ways of relating colored objects. Abstract systems require definition of dimensions and scales. A concrete system is a collection of specimens exhibiting properties specified by the dimensions and scales of an abstract system. The accurate production of such specimens requires a complete written definition of the system, including the specification of all pertinent observing and measuring conditions. The choice of materials requires consideration of the spectral and geometric aspects of the optical nature, some aspects of the mechanical nature, stability, durability, availability, acceptability to users, and cost. The value of color standards depends on the precision and accuracy with which they are produced. Efficient production and long-term reproducibility depend on well-standardized methods of color measurement.

Examination of the receptive field structure of the retina suggested looking at small graphic figures of special forms. The luminance distribution called the “Mexican hat function” was approximated by a black dot with a small white dot at its center, called a “tip,” and the inverse function was approximated by a white dot with a small black dot at its center, called a “pit.” Such figures were given the generic name “tippit.” On a dark-blue ground, tips looked yellow, and on a bright-yellow ground, pits looked blue. Similarly, a black line with a white center, on a blue ground, and a white line with a black center, on a yellow ground, elicited these effects. On yellow and blue grounds, simple, small colored dots looked more like the color of the ground than when seen as large spots on a neutral gray ground, an effect here called “microspreading.” This effect may be attributable to scattering and blurring, but these processes do not account for the tippit effects. The visual system exaggerates contrast between a large spot and ground, and diminishes contrast between a small dot and ground, but exhibits neither effect on a figure of some intermediate size. Chromatic pit lines exhibit effects obeying laws of additive mixture. It appears that perceptions of these effects are normally repressed. No causal link was sought or established between receptive field theory and the observed effects. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 242–250, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10159

Standard sets of metamers are used to test daylight simulators intended for visual appraisal or measurement of color. A new set is proposed and a method is given for evaluating the sensitivity of test metamers to various spectral defects in the visible spectrum. Ideal illuminant spectra were perturbed in specified ways to find the amount of defect tolerated without exceeding a given standard quality category. The amount of perturbation was compared to that tolerated by existing standard metamers, to assure that new metamers grade simulators on the same internationally accepted scale of quality. The method was used to validate metamers designed to assess simulators of CIE Illuminant D50, over the spectral range 400–700 nm, and new metamers designed to assess simulators of CIE Illuminants D50, D55, D65, and D75, over the spectral range 380–780 nm. © 1999 John Wiley & Sons, Inc. Col Res Appl, 24, 322–330, 1999

Part I of this article dealt with the appearance of metallic materials observed at a distance of a few meters. This part deals with the appearance at reading distance. Metallic materials exhibit various appearance attributes, including glitter, glints, depth, coherence glitter, binocular luster, binocular glitter, and binocular mottle. Color disparity is proposed as a measure of binocular luster. Metallic materials resemble grainy photographs, so the method used in photography to quantify graininess by measuring blending distance is introduced. Objective measures of granularity are proposed as correlates of graininess. The term “subsurface” is applied to the apparent “surface” lying beneath the glossy surface. Methods of optical image analysis, such as point spread function, edge spread function, Wiener spectrum, modulation transfer function, and image correlation are proposed to characterize the appearance of metallic surfaces. Polarization and cylindrical presentation may aid measurements. Binocular attributes of appearance introduced here require analysis of the disparity between two points of view. New kinds of pigments may require new methods of measurement. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23: 362–373, 1998

The use and characterization of metallic paints and plastics have been important, particularly in the automotive industry, throughout the last half of this century. The scientific concepts and terminology of this field are still evolving. The principal appearance characteristics of these materials, when viewed at a distance, are luster and goniochromism. Methods of characterizing and measuring metallic surfaces are being standardized by a committee of the American Society for Testing and Materials. New instrumentation has been developed to provide controlled viewing conditions for judging these materials. Modern portable multi-angle measuring instruments are easy to operate and take measurements very quickly. © 1996 John Wiley & Sons, Inc.

For convenience and reproducibility, daylight is artificially simulated for viewing and measuring colors. Daylight has been standardized in a way that is impractical. the evaluation of fluorescent materials requires simulation of the ultraviolet component of daylight or daylight through a window. Sources for viewing are assessed by spectroradiometry and standard computations. Sources for spectrophotometry may be tested the same way or by measuring radiance factors of fluorescent standards. Better manufacturing methods have improved glass filters. A new filter design method takes account of the spatiospectral nature of the source and affords many degrees of freedom.

Munsell started to base his color-order system on measured physical quantities, but it came to represent the order of colors us they ure perceived. The hue circle represents fundamental facts about color vision. The Munsell hue circle has anomalous placement of blue and the use ($five principal hues does not relate to color vision nor applied color science. A reoriented hue circle, labeled with the additive and subtractive primariesblue,green, red, yellow, magentu, and cyan-but retaining the existing Munsell hue spacing and sectors is proposed.The primury hue circle relates to vision and color-reproduction processes, so it should exert a unifying influence on color .science. 0 1993 John Wi1ey . & Sons. Inc..

Equations are given to compute Munsell value from a CIE luminance factor Y. The equations are a very accurate, though not mathematically exact, inversion of the fifth-order equation adopted by the Optical Society of America as the practical definition of Munsell value. The maximum error in Munsell value is 0.0035. The equations have been employed by the Committee on Appearance of the American Society for Testing and Materials.

A simple equation to compute correlated color temperature (CCT) from CIE 1931 chromaticity coordinates x and y is given. Over the range of interest in color science, the errors are negligible. It was derived from the fact that the isotemperature lines for CCTs of principle interest nearly converge toward a point on the chromaticity diagram and the assumption that CCT may be represented by a third-order polynomial function of the reciprocal of the slope of the line from that point to the chromaticity of the light. the equation is useful in designing sources to simulate CIE colorimetric illuminants.