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Continuing a discussion by Kuehni, this note examines the problem of fitting as many as possible colors in a 1-JND radius sphere such that each pair of colors is separated by at least 1 JND. Kuehni announced nine. A first estimate yields a maximum of 13, but this is too many because colors populating adjacent spheres will be too close to each other. Accordingly, I derive the maximum number [ABSTRACT FROM AUTHOR]

The CIE defines chromaticity coordinates as the ratio of each of a set of three tristimulus values to their sum. As shown here, for two-equation systems such as 1964 ( u′, v′), there is always a tristimulus coordinate system that allows this definition to work. However, to include systems like that of MacLeod and Boynton in which three equations define chromaticity, an extension of the CIE definition would require a linear transformation that follows the ratio process. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 317-318, 2014; Published Online 20 December 2013 in Wiley Online Library (). DOI 10.1002/col.21863 [ABSTRACT FROM AUTHOR]

We agree with the main point of Rolf Kuehni's letter; time is ripe to improve the standard lightness metric L*. We discuss items he raised: scientific literature supporting both log and power laws of lightness, the relation of math theory and curve fitting, crispening, different models of lightness for different situations, and 'who cares?' © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 105-106, 2014 [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue including one by Robert B. Mann on quantum entanglement in noninertial frames and another by Edward Apgar on generalization of relativity.

Byrne & Hubert (B&H) assert that reflectances embody the reality of color, but metamerism smears the authors' "real" color categories into uselessness. B&H ignore this problem, possibly because they implicitly adopt a sort of subjectivism, whereby an object is defined by the percepts (or more generally by the measurements) it engenders. Subjectivism is unwieldy, and hence prone to such troubles. [ABSTRACT FROM AUTHOR]

Discusses the application of color perception to a photometer, for which calibration is analogous to socialization of humans to agree in color. Definition of isomorphisms based on color perception; Calibration of photometers.

Opinion. Comments on studies on the psychophysics of nontrivial constraints on color categorization. Frailties in color science; Conditioning forces of modern technology; Fragility of the opponent-color framework.

The article reviews the book "The Structure and Properties of Color Spaces and the Representation of Color Images," by By Eric Dubois.

This poem summarizes the fit-first method of camera evaluation described in Jim Worthey's 'Applications of vectorial color.' The algorithm works with the locus of unit monochromats (LUM) in camera and CIE color-matching spaces. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011; [ABSTRACT FROM AUTHOR]

A one-dimensional box is posited with identical point masses synchronously and elastically hitting each other and opposite ends of the box. From a moving frame, special-relativistic kinematics says the center of mass (CM) of the box (exclusive of the point masses) moves uniformly, but momentum conservation says CM moves jerkily. Hence special relativity does not support momentum conservation. [ABSTRACT FROM AUTHOR]

Presents a commentary on an article about the need for linear basis-function spectra in color constancy according to Roger N. Shepard. Discussion of a natural luminant spectrum as terrestrial transformation of the invariant solar source; Examples of color-constancy models; Use of an illuminant-invariant map based on the analysis of single point in space.

The broadband characteristics of the underwater acoustic propagation channel determine both the approach to communicating and the performance which can be achieved. This paper presents a detailed broadband characterization of the channel and uses this characterization to describe approaches to communication. Performance bounds are calculated and compared to channel capacity results. [ABSTRACT FROM AUTHOR]

Extending previous time-spread work by the present authors [J. Acoust. Soc. Am. Suppl. I 73, S11 (1983)], the frequency spreading of an acoustic signal reflecting from an ocean bottom (in the presence of source and receiver motion) is computed using a simple geometric-acoustic model. In that model, a ray reflects specularly from each bottom facet, and arrives at the receiver if and only if the position and slope of the facet provide the requisite specular path. The model provides a connection between the expected power flux into the receiver aperture from a particular facet and the slope distribution of the bottom (assumed constant in depth). For a cw signal, the frequency spread can be computed by histogramming in Q = (f - f0)/f0 the expected relative energy from a grid of bottom facets. (Here, f0 is the frequency emitted at the source, and f is the frequency of the received signal.) The quantity Q depends only on the position of the facet, range, depth, and source and receiver velocities: it does not depend on f0, so long as the ray paths are independent of frequency, as in the present model. In fact, the expression for Q is the time derivative of delay time for a broadband signal, as well as having a narrow-band interpretation. Computed frequency-spread curves are presented for several source/receiver geometries. Because relative energy vs Q is a function of the channel and not of the sent signal, it may help to connect the broadband scattering function with the expected distribution of power in time and frequency from an input power impulse. [ABSTRACT FROM AUTHOR]

In the International Commission on Illumination (CIE) color appearance model CIECAM02, a modified hyperbolic function is used to represent luminance adaptation. The same nonlinear function is also used in the new color appearance model CAM16 [Color Res Appl., 2017;42:703‐718]. Although the modified hyperbolic function seems reasonable based on physiological evidence, it has an infinite slope at the origin, which causes instability for both the forward and inverse modes of the CIECAM02/CAM16 models. In this article, various possible extensions to the nonlinear luminance adaptation function in CIECAM02/CAM16 are reviewed and evaluated. Based on these investigations, the Gill extension to the hyperbolic function that is used to represent luminance adaptation [Proceedings of 16th Color and Imaging Conference, pp. 327‐331, 2008], is recommended at both the lower end (q < qL) and the upper end (q > qU), where q is the appropriate Rc, Gc, Bc (or Rwc, Gwc, Bwc) response. In addition, the new recommended function can be readily inverted for use in the appropriate inverse appearance model. From an extensive analysis using available experimental data sets, we also propose that, for the lower and upper limits of the luminance range in the extended model, the values qL = 0.26 and qU = 150 be used, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Color‐appearance models, CIECAM02 and CAM16, usually include two one‐step chromatic adaptation transforms: a forward (one‐step) transform to convert data from a first illuminant to CIE illuminant E, plus a reverse (one‐step) transform to convert the results from CIE illuminant E to a second illuminant. In practice, however, one‐step chromatic adaptation models, that avoid the use of the intermediate CIE illuminant E, are also employed. Tests using the one‐step CAT16 model indicate failures of both the symmetry and transitivity properties, except in the case where the degree of adaptation D is equal to unity. The magnitude of these failures depends on the specific illuminants selected, and increases as the degree of adaptation decreases. From four possible two‐step CAT16 models, we have identified two that obey the symmetry and transitivity properties, one with slightly better predictions of the experimental corresponding‐color datasets available in the literature, and more consistent with the one‐step CAT16 model. The findings of this article confirm that, for incomplete adaptation, the use of the one‐step CAT is incorrect, and we propose that the use of a two‐step CAT16 model be mandatory for future applications. [ABSTRACT FROM AUTHOR]

The CIECAM02 color-appearance model enjoys popularity in scientific research and industrial applications since it was recommended by the CIE in 2002. However, it has been found that computational failures can occur in certain cases such as during the image processing of cross-media color reproduction applications. Some proposals have been developed to repair the CIECAM02 model. However, all the proposals developed have the same structure as the original CIECAM02 model and solve the problems concerned at the expense of losing accuracy of predicted visual data compared with the original model. In this article, the structure of the CIECAM02 model is changed and the color and luminance adaptations to the illuminant are completed in the same space rather than in two different spaces, as in the original CIECAM02 model. It has been found that the new model (named CAM16) not only overcomes the previous problems, but also the performance in predicting the visual results is as good as if not better than that of the original CIECAM02 model. Furthermore the new CAM16 model is simpler than the original CIECAM02 model. In addition, if considering only chromatic adaptation, a new transformation, CAT16, is proposed to replace the previous CAT02 transformation. Finally, the new CAM16-UCS uniform color space is proposed to replace the previous CAM02-UCS space. A new complete solution for color-appearance prediction and color-difference evaluation can now be offered. [ABSTRACT FROM AUTHOR]

Metrics of color-difference formula improvement (i.e., standardized residual sum of squares and Pearson product moment correlation) are shown to convey the same information. Furthermore, each metric has two computational forms that assume different linear data models, specifically, with or without an ordinate intercept. It is essential to choose a computational form that matches the data model. We recommend explicitly declaring whether or not the data have been centered, i.e., by subtracting the mean value from each datum, to match the intercept-free data model. Statistical testing of the metrics assumes independent, normally distributed randomness of residuals from the data model, and homogeneous variance. Procedures consistent with these assumptions include robust statistical tests, homogenizing data transformations, and meta-analysis.