Methods for optimal color selection

The color characterization of digital cameras often re- quires the use of standard charts containing a fixed number of color samples. The exact choice of such characterization charts—how many (and which) known samples to include—is known to affect characterization performance. This study describes methods to se- lect optimum color samples from a set of 1269 Munsell surface col- ors. The effect of sample selection on characterization performance is evaluated and compared with performance using the standard GretagMacbeth ColorChecker and GretagMacbeth ColorChecker DC colors. The work confirms that the standard charts appear to have been well selected. However, we show that it is possible to select 24 samples from the Munsell set that outperform the Gretag- Macbeth ColorChecker and that this selection can be efficiently de- rived using an algorithm called MAXMINC. It is proposed that this al- gorithm may have general applicability; for example, to the optimal selection of samples constrained to be a subspace Munsell color solid. © 2006 Society for Imaging Science and Technology. DOI: 10.2352/J.ImagingSci.Technol.200650:5481 the ANSI IT8 charts are designed to be used in a color- management process with the aim to allow a system to re- produce colors with acceptable tolerance. These charts are typically checkerboard array targets containing a number of carefully selected and prepared squares or chips in a wide range of achromatic and chromatic colors. Many of these square patches represent the color of certain natural objects of special interest, such as human skin, foliage, and blue sky. 11,12 Primary colors for both additive and subtractive color mixing are also commonly included. A series of ach- romatic patches in the characterization charts provide a con- venient grayscale that may be used for color balance and tone-reproduction purposes. Repeated white, midgray, and black patches around the outer edge of the chart (Gretag- Macbeth ColorChecker DC, for example) allow measure- ments for spatial uniformity of illumination. Special colors, such as glossy surface colors in the GretagMacbeth ColorChecker DC and optional vendor colors in the ANSI IT8 charts, can also be included.

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