Hugh S. Fairman

Handling translucent specimens in an opaque Kubelka–Munk Environment

Computer-color matching usually employs a subset of Kubelka–Munk equations which require that each specimen analyzed be at complete hiding. This set of equations is preferred because they are simpler than their counterpart equations that operate at incomplete hiding. On the other hand, in coatings and plastics very often colorant specimens must be utilized that, either because of their nature or concentration, fail to qualify as being at complete hiding. This communication examines techniques for handling such cases and makes recommendations for obtaining the theoretical opaque reflectance of the specimens from measurements over both black and white. In addition, the article recommends a new relationship that more aptly characterizes the contrast ratios required than previous methods have done.

Leonardo 2000: the softcopy screen book

As part of a larger project that is intended for self-taught color science, we developed a software tool to provide a softcopy simulation of the Munsell Book of Color under varied illuminants and for various observers. This simulation avoids setting up as ideal a particular set of pigments from which to derive spectral reflectances. The color-order database contains a reflectance function for each Munsell aim point. The aim points are the usual ones for Illuminant C and 2° Observer function. For a new illuminant and observer, each reflectance funtion is weighted by appropriate color-matching function and illuminant spectral power distribution, and integrated to produced new X, Y, and Z values. From these values, CIELAB and chromaticity coordinates are computed. Having specified atlast colors in a variety of coordinates, the program next renders them on screen as a color-navigation tool. To illustrate good practice in constructing an atlas of reflectances, the reflectance spectra from a linear series of aim points in Munsell space can be co-plotted to show the requirements for consistency of the series under illuminant and observer change.