Abstract
Object color space is highly structured due to optical constraints (radiant power non-negative, reflectance factors between zero and unity) and ecological context (daylight illuminant). In this setting trichromacy induces a natural geometry through a unique spectral tripartition. Different from null-context colorimetry, one gains two desirable relations: The colorimetric coordinates are coarse-grained spectral reflectance factors and there is a direct link to color experiences, since RGB–coordinates provide ostensive definitions. The framework allows one to deal with subtractive color mixture, source variation, effects of metamerism and relations between scenes and image data in a unified, structured manner. In ecological contexts, colors are effectively object properties. The formal framework is linear algebra and convex geometry. Applications in human biology, computer graphics, design, etc., are immediate.
Highlights
Are colors object properties? Answers depend on the intended ontological roots
The canonical description of the space of object colors is—by way of the maximum volume crate crate[R, G, B]—augmented by the Euclidean geometry to make it into the unit cube. This metric has nothing to do with phenomenology, psychometrics, or eye measure. It derives from colorimetry, physical constraints and a conventional radiant source [E(λ) or average daylight serve fine.] Anyone can repeat this construction on a deserted island, starting from any set of color matching functions and will end up with the same result
Note that there are four distinct types of semichromes. This is most understood by using the slide rule to check when the pass band meets the spectrum limits at either side. These types are the essentially different families of spectral reflectance factors, important qualitative object properties: FIGURE 9 | The “chromaticity diagram” introduced in this figure is a view of the color solid from ∞ along the KW–Hering axis
Summary
Are colors object properties? Answers depend on the intended ontological roots. Instances are “physical colors” (radiant power spectra and spectral reflectance factors), “colorimetric colors” (like red, nominal; RGB[99|00|00], quantitative; Section 4.2) and “phenomenological colors” (Yred, where “Y” stands for experiential quale or ostensive in intersubjective communication, Section 1.1). Answers depend on the intended ontological roots. Instances are “physical colors” (radiant power spectra and spectral reflectance factors), “colorimetric colors” (like red, nominal; RGB[99|00|00], quantitative; Section 4.2) and “phenomenological colors” (Yred, where “Y” stands for experiential quale or ostensive in intersubjective communication, Section 1.1). The first two bridge physics and physiology, the third one physiology and phenomenology. Image science, computer graphics (CG) and ecological biology/psychology involve all. Balanced accounts of such diverse interrelations are rare. We present a minimalist formal account, with various novel developments
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