bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence theory for color constancy models
Authors: Stine Wm. Wren , Sparrow John E.
Published: June 2007

The problem that color constancy models address is one of recovering the reflectances of a surface under different illuminants and spatial configurations. As models of the human visual system, they should recover surface reflectances when the human visual system recovers those reflectances and fail when the human visual system fails to recover those reflectances. Unfortunately, it is difficult to determine just when these models will recover surface reflectances and when they will fail. We introduce a theory of influence that quantifies the degree to which the lightness calculated for a given surface element is influenced by the receptor responses to other elements. Influence theory is shown to be a very useful tool for highlighting testable predictions that can discriminate among color constancy models without having to determine directly when they will recover surface reflectances. This technique for generating empirical predictions is demonstrated by studying the effects of choosing different normalizing functions on an asymptotic retinex algorithm.
Artificial daylight for measurement of optical properties of materials
Authors: Terstiege Heinz
Published: June 2007

Radiometric properties of materials for lighting and building have to be known in the UV, visible, and IR regions of the spectrum. Radiometric and photometric properties can be measured with spectrometers independent of the spectral power distribution of the irradiating source used for measurement provided there is sufficient radiant energy available at all measured wavelengths. However, for luminescent materials a precise simulation of the reference illuminant has to be used for measurement, otherwise the measured characteristics are meaningless.
An evaluation of methods for producing desired colors on CRT monitors
Authors: Post David L. , Calhoun Christopher S.
Published: June 2007

Three experiments were performed to evaluate methods for generating colors having desired CIE chromaticity coordinates and luminances on CRT monitors. Methods based on piecewise linear interpolation were found to yield better accuracy than others based on linear regression. Comparisons between two monitors revealed no substantial differences in accuracy, but the monitor's state of adjustment was found to have important effects. Evidence was also obtained concerning the number of CRT measurement points needed to obtain maximum accuracy from the interpolation‐based methods. The methods' accuracies are characterized and avenues for improvement are suggested.
A planar‐vector based color space for graphic arts color analysis and reproduction
Authors: Huntsman James R.
Published: June 2007

A new color space is developed, based on a model of a trigonally symmetric, planar arrangement of three response vectors, which first separates a visual stimulus via tristimulus values into achromatic and chromatic components and then recombines them. Because three visual response vectors are mutually opposed, the model is called the mutually opposed, trichromatic response (MOTR) model. The MOTR model does not introduce any new visual concepts but rather uses established concepts in an empirically different way. The MOTR model directly represents a color as a combination of two chromatic primaries and one achromatic primary. It is, therefore, particularly useful for halftone color reproduction based on two primary colors plus black, sometimes referred to as 100% GCR (gray component replacement). It is useful also because of its linearity properties between lightness and the chromatic and achromatic contents. The MOTR model's color space is applicable to existing color‐order systems and provides a graphic representation often better than CIELAB and CIELUV do. The MOTR model is also consistent with many known visual characteristics such as unique hues, illuminant adaptation, wavelength discrimination, and defective color vision. The model as described herein is limited to the comparison of related colors under a given photopic luminance.
Color in the hands of the artist and eyes of the beholder
Authors: Jameson Dorothea
Published: June 2007

The perceptual effects that inform a series of paintings are analyzed and described using the tools of the visual psychologist and psychophysiologist.
Unique hue loci and implications
Authors: Ikeda M. , Uehira I.
Published: June 2007

Unique hue loci of red, yellow, green, and blue were obtained for lights of 0.5 and 2 cd. m‐2 from five normal color vision subjects. Most loci curved on the chromaticity diagram. This result excludes linear equations of colormatching functions as candidates for spectral sensitivity functions of opponent color systems, (r/g)λ and (y/b)λ. The chromatic valence curves of two opponent color systems obtained by the so‐called cancellation experiment were analyzed in relation to the unique hue loci and it was shown that the appearance of the valence curves can be manipulated at will by choosing the cancellation light at various points on the chromaticity diagram. A similar manipulation was also demonstrated for the additivity property of chromatic valence and it was made clear that no unique solution is obtainable.
R/G and Y/B opponent‐color mechanisms revealed in temporal integration for bichromatically mixed lights
Authors: Kawabata Yasuhiro , Aiba Thomas Satoru
Published: June 2007

In the present study, the critical durations for temporal integration at theshold were obtained for bichromatically mixed (red/green and yellow/blue) test lights presented against darkness and achromatic backgrounds of different intensities. Critical durations crucially depended on the mixing ratio of the red and green components: it was shortest when red and green components were balanced in intensity canceling chromaticness of both components, and longer for red and green monochromatic lights. This trend was pronounced with backgrounds of higher intensities but was not obvious with dim backgrounds. The results of yellow/blue condition showed that critical durations were shorter when yellow component was dominant, as well as when yellow and blue components were balanced in intensity canceling chromaticness of both components, but when blue monochromatic light was dominant, it was longer than in other mixture conditions and changed less with the elevation of the background intensity. The results were interpreted as demonstraing the red/green and yellow/blue opponet‐color mechanism's participation.
Color notation by visual interpolation in colour order systems: How accurate is it?
Authors: Döring Günter
Published: June 2007

Systematic collections of colour samples from colour order systems are used in many cases, e.g., in architecture and in design. Usually, the colour that a designer has in mind is not found as a colour sample within the collection at hand, but has to be determined by visual interpolation between the available samples. However, because the colour coordinates of the available samples deviate from those of the aim points, these deviations give rise to uncertainties during visual interpolation.

I have investigated the influence of the colorimetric accuracy of the colour samples in the collection used on the precision of colour notation by visual interpolation. This research shows that the accuracy of notation by visual interpolation is not influenced by the colorimetric precision of the colour collection alone, but also by the magnitude of the colour differences between adjacent colour samples in the respective colour collection and by the directions of the colour differences from the aim points.
Coexisting or mingling: The visual aspect of the problem in the urban context
Authors: Tosca Theano Fanny
Published: June 2007

The residents of a working‐class settlement in the north of Greece were the subjects of a three‐stage study to determine the degree of satisfaction these people found in their surroundings. The ultimative objective was to take a highly disparate group of individuals and unify them both as a community and with the surrounding Greek population by designing an environment that blends the individuals' colour tastes. The main aspects of the investigation were (a) the residents' use of public spaces, (b) their evaluation of them from functional, psychological, visual, and aesthetic points of view, and (c) their colour preferences (colour palette and combinatory principle) for building exteriors. The second and third stages of the research focussed on, respectively, semantic differentiation and an analysis of a sample building facade by colour elements. The main difficulties in this research resulted from the very disparateness of the population (refugees of various origin), the indifference of the authorities, and the bissection of the area by a highway. In the coloration proposals resulting from the research, the accomplishment of the main objective on the level of the visual and psychological reaction of the users to an organic coloration of their building facades was attempted. Social, semantic, synthetic, and technical factors were taken into account.
Analysis of white point and phosphor set differences of CRT displays
Authors: Engeldrum Peter G. , Ingraham John L.
Published: June 2007

There are a variety of CRT phosphor sets used to display color information. In addition, the white point, achieved when the red, green, and blue phosphors are excited by beam currents corresponding to the maximum digital count for each primary, is not standardized. Displaying a file containing RGB digital values on unlike monitors, with different phosphors and/or white points, would produce different colors. Computer stimulations were conducted to compute the colors for CRTs with different phosphor sets and constant white points and for different white points with contant phosphor sets. Test results demonstrated that CIE‐LAB color differences were larger when the phosphor sets were different. Smaller color differences resulted from differences in white point, assuming a constant phosphor set. Overall average color differences were reasonably represented by a linear relationship to the average color difference between the phosphors. A linear relation was also found between the average color differences and the color differences between the white points. It was concluded that phosphor differences contribute more to color differences, and therefore standardization efforts should focus first on adopting a color phosphor set, and secondly on a white point.
ASTM standards on color‐difference measurements
Authors: Billmeyer Fred W. , Hammond Harry K.
Published: June 2007

For some time, the only documentary standard on color‐difference measurements within the American Society for Testing and Materials (ASTM) has been D 2244, “Method for Calculation of Color Differences from Instrumentally Measured Color Coordinates.” It was developed by ASTM Committee D–1 on Paint and Related Coatings and Materials, and currently includes only the three color–difference equations of particular interest in the paint industry, namely CIELAB, Hunter Lab, and FMC‐2. ASTM Committee E‐12 on Appearance plans to prepare a comprehensive standard, probably a Guide to the Selection and Use of Color‐Difference Equations. It will contain not only the three equations mentioned above but also a number of others. The Guide will also include tutorial discussion on the selection of equations for various color‐difference evaluation purposes. This article documents the history of color‐difference standards within ASTM. It also invites readers to contribute suggestions for material to be included in the proposed Guide.
Color‐appearance model and chromatic‐adaptation transform
Authors: Nayatani Y. , Takahama K. , Sobagaki H. , Hashimoto K.
Published: June 2007

A nonlinear color‐appearance model was extended to apply to white and light‐gray background. Based on this extended model, two kinds of chromatic‐adaptation transforms were derived, which correspond to lightness‐chroma match and brightness‐colorfulness match. The chromatic‐adaptation transform for lightness‐chroma match is also an extension of the transform proposed by CIE for further testing. The differences between the two transforms were confirmed by visual observations. The usefulness of a combination of a color‐appearance model and its corresponding chromatic adaptation transform is discussed. In addition, the practical importance of brightness and colorfulness is discussed.
Comparison of color‐appearance models
Authors: Nayatani Yoshinobu , Mori Toshinori , Hashimoto Kenjiro , Takahama Kotaro , Sobagaki Hiroaki
Published: June 2007

The color‐appearance models developed by R. W. G. Hunt (model H) and Y. Nayatoni and his collaborators (model N) are compared. The following color perceptions are analyzed: (1) colorfulness under illuminant C for NCS samples, (2) colorfulness change by changing illuminant C to illuminant A, (3) colorfulness change by changing adaptign illuminance, (4) Helson‐Judd effect on achromatic colors under saturated chromatic illuminants, and (5) brightness and lightness. Special features of each model are made clear. In addition, a deatailed discussion is given on the mechanism introbucing the Helson‐Judd effect and on the model formulations, especially in model H.
Test for a correlation between VΛ and the + y opponent‐channel sensitivity
Authors: Ingling Carl R. , Martinez‐Uriegas Eugenio , Grigsby Scott S.
Published: June 2007

Rushtion and Baker have shown that the ratio of R to G cones varies between observers. We use this variability to ask if observers, say, who are rich in R‐cone input to the flicker (VΛ) channel, are also likely to be rich in R‐cone input to the long‐wavelength half of the y‐b channel. For the 8 observers tested, there is no correlation between cone inputs to +y and VΛ.
Comparison of the munsell, NCS, DIN, and coloroid colour order systems using the OSA‐UCS model
Authors: Smith N. S. , Whitfield T. W. A. , Wiltshire T. J.
Published: June 2007

An earlier article described the use of a colour notation conversion program to measure the accuracy of the NCS, DIN and OSA‐UCS color atlases. This article describes the application of the same program to compare the perceptual scaling of the Munsell, NCS, DIN, and Coloroid systems with that of the OSA‐UCS system. Five OSA‐UCS cleavage planes were selected which represent a varied but systematic sampling of OSA‐UCS colour space. The samples contained on these planes were converted onto the colour spaces of the Munsell, NCS, DIN and Coloroid systems. The converted points have been displayed graphically for ease of comparison.
The purkinje effect: Some considerations on the interplay of receptoral and postreceptoral mechanisms
Authors: Ronchi Lucia R.
Published: June 2007

A heterochromatic brightness or lightness match, established at photopic levels, is not expected to hold at lower adapting luminances. This applies, in particular, to the Purkinje Effect, concerning the red‐blue comparison. The fact that a “blue” stimulus mainly involves the shorter wavelengths favors the interpretation in terms of rod intrusion, coming gradually into play as the eye, pre‐adapted to a photopic level, is becoming adapted to a mesopic or scotopic one. The two experiments described in this paper aim to put into evidence some effects that are likely to be due to postreceptoral mechanisms, and which may confuse the student faced with a practical demonstration of the Purkinje Effect. In particular, we consider the blue lightness enhancement after an abrupt decrease in adapting luminance, and the decay of lightness‐luminance discrepancy of narrow‐band stimuli during the recovery period.
Comparison of reference‐white standards for video display units
Authors: Brill Michael H. , Derefeldt Gunilla
Published: June 2007

There are two common chromaticity standards for video‐display‐unit reference white, one standard at 6500 K correlated color temperature (CCT), called D65 for short, and the other, an industrial standard, at 9300 K CCT. The choice of D65 evolved from the NTSC specification for television receivers based on Illuminant C—an average daylight at 6800 K CCT. Although originally the studio illumination was much redder than D65, modern television cameras operate in daylight, so a daylight white standard is most likely to allow exact color reproduction at the receiver. Hence average daylight is the most natural white point. However, many manufacturers chose 9300 K because the chromatic efficiency of the prevailing blue phosphors was greater than that of red or green phosphors, because viewers did not object to a blue color bias, and because 9300 K was bluer than any of the prevailing ambient illuminations. In the years since the adoption of the 9300‐K standard, these facts underwent some change, and also VDUs came to be used for graphics as well as for television. This paper outlines the reference‐white problem, and suggests a reevaluation of the 9300‐K standard.
Construction of discrimination ellipsoids for surface colors by the method of constant stimuli
Authors: Indow Tarow , Morrison Melvin L.
Published: June 2007

First, methods to define the region of colors indistinguishable from a standard color are reviewed, both for aperture and surface colors. Then, an algorithm to define discrimination ellipsoids for surface colors in (x,y,l) space is described, where 1 is a function of Y. The data are a set of Pi, the proportion that a comparison stimulus si is judged discriminable from a standard stimulus So (the method of constant stimuli). An ellipsoid is defined around So such that, if the distance between So and si is evaluated by the radius of the ellipsoid in that direction, then that distance is related to Pi in the form of a sigmoid curve (the cumulative normal distribution). The third axis of the ellipsoid is defined to be parallel with the Y axis and hence there are four free parameters. These parameters are estimated using the principles of either chi‐square minimum or maximum likelihood estimation. The algorithm was applied to the data obtained from, respectively, R.M. Rich, D.C. Rich, and Witt and Döring. Results by the present method were compared with their results, which were obtained using different procedures. The method was also applied to the data of Bartleson to test the possibility that the domain of colors called “brown” is ellipsoidal in form; the result was negative. A theoretical discussion on the naure of the sigmoid curve is included.
Structural correspondence between music and color
Authors: Sebba Rachel
Published: June 2007

The article outlines the features that are typical of the attempts to bridge between music and color on the artistic and scientific levels. It emphasizes the importance of clarifying the factors common to color and sound both for the purpose of understanding the communication codes of arts as well as for the development of syntax for expression in colors. The article adopts Gombreich's approach to investigate the connection between music and color through comparison of the relationships between the elements and not through comparison of the elements themselves. The article presents an experiment that examines how the organization of the sounds in a musical piece is expressed in color design: (1) How the overall impression of a piece of music is expressed in the choice of colors and in their reciprocal relationships; (2) What are the characteristics of color scales that were shaped according to a musical scale; and (3) What is the visual effect of a color scheme that was built according to the formation of notes of the musical piece.
Quantifying colour appearance. Part I. Lutchi colour appearance data
Authors: Luo M. Ronnier , Clarke Anthony A. , Rhodes Peter A. , Schappo André , Scrivener Stephen A. R. , Tait Chris J.
Published: June 2007

The work described here forms part of a research project entitled Predictive Perceptual Colour Models. The aim of this project is to develop a colour appearance model capable of predicting changes of colour appearance under various different viewing conditions. This will provide industry with a quantitative measure for assessing the quality of colour reproduction and enable more rapid and accurate proofing simulations in the graphic art industry. A large‐scale experiment has been carried out in which colour appearance was assessed under a wide range of viewing conditions. The parameters studied were (1) D65, D50, white fluorescent, and tungsten light sources, (2) luminance levels of about 40 and 240 cd/m2, (3) five background conditions: white, grey, black, grey with white border, and grey with black border, and (4) two media: luminous colours (displayed on a high‐resolution colour monitor) and nonluminous colours (presented in a viewing cabinet). Each colour was assessed by a panel of six or seven observers using a magnitude estimation method. In total, 43,332 estimations were made, and these form the LUTCHI Colour Appearance Data. Data analysis has been carried out to examine the reliability of the experimental results and to understand the effects of the various viewing parameters studied. (Part II of this article describes how the LUTCHI Colour Appearance Data has been used to test the performance of various colour spaces and models.
Angular reflectance distributions for coloured newsprint
Authors: Gardner James L. , Shaw John E. , Bonham James S.
Published: June 2007

Angular distributions of light reflected from coloured paper surfaces have been measured at three wavelengths in the red, green, and blue regions of the spectrum. These distributions are fitted as the sum of cosine and high‐order cosine terms to describe the diffuse and specular components, respectively. The fitted distributions are used to estimate colour errors for various angular separations of illuminating and viewing beams, and are qualitatively described in terms of scattering and absorption in the paper.
Color harmony attributes
Authors: Burchett Kenneth E.
Published: June 2007

A content analysis of nine books on color is used to confirm the multifarious nature of color harmony. Different meanings of the harmony concept are distributed over twelve attributes. Results are condensed into six unique domains to encompass all meanings of color harmony.
Visual determination of suprathreshold color‐difference tolerances using probit analysis
Authors: Berns Roy S. , Alman David H. , Reniff Lisa , Snyder Gregory D. , Balonon‐Rosen Mitchell R.
Published: June 2007

As part of a research program to improve the relationship between visual and numerical color‐difference evaluation for industrial colorimetry, a color‐difference tolerance data set for fitting and testing of color‐difference metrics has been extended to include 156 individual color‐tolerance determinations. These tolerances were designed to sample 19 color centers over a surface color gamut with balanced sampling of lightness and chromaticness differences. The tolerance determination procedures emphasized accurate estimation of population visual color‐difference response and rigorous estimation of tolerance precision. Tolerance accuracy was confirmed by excellent agreement of these results and the majority of previous experiments on five color centers selected for CIE color‐difference evaluations. The average uncertainty of the tolerance determinations was ± 11% of the tolerance value at a 2 ó level (95% confidence interval). The completed data set is suitable for estimating the parameters of color‐difference metrics or testing the performance of such metrics. The color tolerances indicated the systematic lack of uniformity of the CIELAB space, in general agreement with previous experiments. A simple modification of the CIELAB color‐difference metric was shown to account for much of the systematic lack of uniformity.
An evaluation of some tristimulus weights
Authors: Stearns E. I.
Published: June 2007

Tristimulus values were calculated for the 1964 observer and illuminant D65 for four theoretical specimens, with radiance factor data of 1‐nm bandpass width, by the CIE recommended procedure and used as accurate references. Tristimulus values were then calculated for the same four theoretical specimens with six sets of published weights, with radiance factors assumed to have a bandwidth equal to the measurement interval and the bandpass profile to be triangular. The difference of the wide bandwidth calculated tristimulus values from the reference tristimulus values was considered to be an error and was expressed as CIE L*a*b* color difference.
The chroma sensor® CS‐5: A tradition of improved performance
Authors: Rich Danny C.
Published: June 2007

In a previous article [R. Stanziola, B. Momiroff, H. Hemmendinger, Color Res. Appl. 4, 157–163 (1979)], a new generation of scanning spectrophotometer was described. The new generation instrument contained many improvements to the recording spectrophotometer designed by A. C. Hardy. This article describes the progeny of that generation. Continued improvements in both optics and electronics have been implemented so that the routine performance of the CS‐5 now far exceeds the ability to make and judge colored specimens.
Recommended terminology for matrix R and metamerism
Authors: Fairman Hugh S.
Published: June 2007

In recent years new terminology for metamerism and related phenomena has been put forth. Terms associated with these phenomena are presented in the form of recommendations from ISCC Committee #27: Indices of Metamerism. The terms are given with a definition and where appropriate a symbol is recommended. A subject closely allied to metamerism is Cohen and Kappauf's spectral decomposition theory, often referred to as Matrix R theory. Terms, symbols, and definitions associated with this subject are additionally recommended. The recommendations are made in the interest of uniformity of future practice on the part of writers and users.
Back to Helmholtz
Authors: Vos J. J. , Walraven P. L.
Published: June 2007

The coincidence of the attribution of the Deane B. Judd AIC Award with the centennial of Helmholtz's line element for color metrics was an incentive to rewalk our own pathway through color science and show it to come back, after some detours, to Helmoltz.
Predicting the lightness of chromatic object colors using CIELAB
Authors: Fairchild Mark D. , Pirrotta Elizabeth
Published: June 2007

A metric of perceive lightness of object colors, L**, is derived and evaluated. This metric, based on CIELAB parameters, is designed to predict the Helmhltz‐Kohlrausch effect whereby chromatic object colors appear lighter than achromatic object of the some luminance factor. Models were fitted to published data and then tested with results from a new lightness‐matching experiment that is described in this article. The L** metric predicts perceived lightness to within the interobserver variability and provides a simple, practical measure of this appearance attribute.
Toward a more accurate and extensible colorimetry. Part I. Introduction. the visual colorimeter‐spectroradiometer. Experimental results
Authors: Thornton William A.
Published: June 2007

A bright ten‐degree split‐field colorimeter is used to study pairs of visually‐matching lights. This colorimeter is coupled by quartz light pipe to a spectroradiometer, and yields accurate absolute spectral power distributions of every viewed light. Six normal human observers use three disparate sets of spectral primaries. In Part I of the article thorough descriptions of the instrument, its calibration, and experimental results are presented. (1) By the Maxwell method, sets of 28 three‐band lights, each light matching a broadband reference‐white light, are obtained. From these sets are found strong and unexpected dependence of perceived brightness per watt on spectral content, and large systematic errors in computed chromaticity (1964 CIE Observer). (2) From sets of white two‐band lights, each matching the broadband reference light, large differences in wavelength of the visually complementary spectral lights, from those indicated by the 1964 CIE chromaticity diagram are found. (3) Sets of Maxwell‐method and maximum‐saturation‐method color matching functions are obtained for each primary‐set and for each observer. (4) Study, at the colorimeter, of perceived brightness of spectral lights in isolation yields three‐component perceived‐brightness‐per‐watt curves like those of Stiles and Crawford of 1933. (5) Perceived brightness of 3‐band white mixtures always increased upon removal of any one of the three spectral components, in agreement with MacAdam's findings of 1950. (6) Visual tests were made of Grassmann's additivity assumption, and of Maxwell spot phenomena. Part II includes discussion of chromaticity and brightness errors and of other aspects of colorimetry problems‐transformation of primaries, structure and shape of the chromaticity diagram, and normalization of color matching functions. Part III gives avenues of possible improvement and general comment.
Perceived lightness of chromatic object colors including highly saturated colors
Authors: Nayatani Yoshinobu , Gomi Yutaka , Kamei Masaaki , Sobagaki Hiroaki , Hashimoto Kenjiro
Published: June 2007

A model was formulated for predicting the Helmholtz‐Kohlrausch effect or the Y tristimulus values for chromatic object colors with the same perceived lightness (L/Y ratios). the model was extended from the previous one in Color Res. Appl. 16, 16‐25 (1991), making it possible to estimate the Helmholtz‐Kohlrausch effect on chromatic object colors with any Munsell Value. By analyzing the two experiments by Wyszecki and by Sanders and Wyszecki using the extended model, the model parameters were estimated for each experiment. By using each of the two estimated equations, L/Y ratios for Y = 20.0 were predicted in the whole chromaticity gamut corresponding to the two kinds of experimental results. the derived contour lines for equal L/Y ratios correlated well with those estimated directly from each experimental data. In addition, extrapolated L/Y ratios for spectral colors with Y = 20.0 showed very good agreement with the luminance ratios for equally bright spectral stimuli, so‐called brightness/luminance (B/L) ratios, derived from the luminous efficiency functions Vb,2(Λ) by CIE TC 1‐02 and Vjudd(Λ) proposed by D. B. Judd.
Munsell value as explicit functions of CIE luminance factor
Authors: McCamy C. S.
Published: June 2007

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.
Discrimination of colours presented against different coloured backgrounds
Authors: McFadden Sharon
Published: June 2007

Colour electronic displays are being used increasingly for information presentation in a wide range of applications. A prerequisite to the effective use of colour coding is that the colours be discriminable under all of the conditions in which the display will be used. For applications such as radar, medical imaging, or electronic charts, different coloured areas may be juxtaposed and coloured symbols superimposed on a multicoloured background. Under such conditions, the colours in the display may affect the appearance and discriminability of each other. the present article examines the extent to which a set of colours that is clearly distinguishable when presented against a uniform background might be confused when the members are presented against differently coloured backgrounds. This was achieved by measuring the range of chromaticities, presented against a grey background, that would be confused with each of the test colours when they were presented against different chromatic surrounds. the findings were used to derive the characteristics of sets of colours that should be discriminable in a complex display.
Numerical methods for colorimetric calculations: A comparison of integration methods
Authors: Smith Brent , Spiekermann Charles , Sember Robert
Published: June 2007

Numerical methods for estimating colorimetric integrals using various data intervals are reviewed. Accuracy of Newton‐Cotes and Gaussian numerical integration algorithms are compared. Tables of calorimetric data for performing Gauss‐Legendre integration are presented. Appropriate numerical examples are presented and applicability to general and special cases is discussed. the B‐spline method of integration is presented. Errors of integration are quantified and discussed. © 1992 John Wiley & Sons, Inc.
A colour notation conversion program revisited
Authors: Smith N. S.
Published: June 2007

Details of an expanded and improved computer program for the interconversion of colour notations are presented. This article describes the inclusion of the Colorcurve, SCA 2541, and HunterLab systems, expansion of the DIN and RAL implements, extension of the NCS aim point database, improvements to the OSA‐UCS and Coloroid conversion algorithms, a direct spectral curve input facility, and the inclusion of CIELAB, CIELUV, HunterLab, CMC[1:1], FMC‐1, and FMC‐2 colourdifference formulas. © 1992 John Wiley & Sons, Inc.
Colour‐difference measurement: The sensitivity of various instruments compared
Authors: Raggi Andrea , Barbiroli Giancarlo
Published: June 2007

Because of the progress in electronic technology and the increasing importance of colour quality control in various branches of industry, over the last decades several colour‐measuring instruments have been developed, each one with its own design features; the lack of standardization among them might be an obstacle to the spread of colour quality control as a means for product qualification. Colour‐difference measurements taken with 11 different models of spectrophotometers [four with 45 (circumferential)/0 geometry and the others with diffuse geometry] were compared with the aim of analyzing their correlation and dispersion. In order to cover different colour‐space regions, measurements were taken on test panels painted with four saturated basic hue (red, yellow, green, and blue) acrylic products gradually modified by adding white or black paint. Basic statistical analyses made on colour‐difference values (ΔE*ab, ΔL*, Δa*, and Δb*) resulted in a high correlation among the examined instruments, but a certain variability, particularly as far as certain hues are concerned.
Extension of dominant wavelength scale to the full hue cycle and evidence of fundamental color symmetry
Authors: Pridmore Ralph W.
Published: June 2007

Dominant wavelength is a psychophysical scale presently limited to the spectrum. It is extended into the nonspectrals to designate the hue cycle in a continuous wavelength‐based scale. To omit the fading spectrum ends, the extended scale is based on the limited spectrum of optimum color stimuli (442–613 nm). The hue cycle interval is found by many methods in agreement, e.g., from the spacing of the ideal primaries (additive and subtractive). These were recently defined as the complementary maxima and minima of several visual functions (e.g., saturation/W, spectral sensitivity, λ discrimination, complementary efficiency). Five of these six primaries are spectral, uniformly spaced at (40 ± 4) nm intervals. Interpolating the sixth (531 c magenta) as similarly spaced between adjacent primaries (blue 447 nm and red 607 nm) gives it the dual designation 407/647 as both ends of the cycle, an interval equivalent to 240 nm. Nonspectral hues are numbered serially with wavelength by interpolating green–purple complementary pairs as sinusoidallike spectral pairs. Applying the extended scale to a color circle, the six primaries reveal a sextuple symmetry of (60 ± 2)°. Only these three pairs are both complements and opposites. In a graph (hue cycles as x and y axes) of x + y color‐mixture, loci of constant λ center symmetrically on the RGB primaries near 607, 531, 447 nm. © 1993 John Wiley & Sons, Inc.
The CIE 1931 standard colorimetric observer: Mandatory retirement at age 65?
Authors: Fairchild Mark D.
Published: June 2007

The CIE system of colorimetry has been stretched to applications in industries and technologies that were not even envisioned when it was established in 1931. In general the standard observer has made this stretch gracefully. However, there has been a rash of recent articles in this and other journals suggesting that perhaps it is time to force the standard observer to retire. Often the apparent failings of colorimetry are due to its improper application or unrealistic expectations. This Color Forum reviews the status of the CIE standard observer and suggests that, while improvements are certainly possible, retirement would be premature.
Measuring color‐matching functions. Part II. New data for assessing observer metamerism
Authors: North Amy D. , Fairchild Mark D.
Published: June 2007

The Munsell Color Science Laboratory model and visual colorimeter for collecting color‐matching‐function data were described in Part I of this article. The model and instrument have demonstrated results that correlate well with data collected using the National Research Council of Canada's Trichromator. Color‐matching‐function data for 18 observers and 20 repetitions on a single observer have been obtained using the Munsell Color Science Laboratory visual colorimeter. The variability for the single observer for 20 repetitions over a month's time was found to be similar to the uncertainty of matching within a single measurement session. The variability of the 18 observers was found to be much larger. The results were compared with the CIE Standard Deviate Observer. The variability of the CIE Standard Deviate Observer was on the order of the single observer variability while the multiple observer variability was significantly larger.
Sensitivity loss and adaptation within the short‐wavelength cone pathway
Authors: Finkelstein Marcia A.
Published: June 2007

Two‐color increment threshold data are used to develop a model of sensitivity control in short‐wavelength detection. The model includes two sites of compressive nonlinearity. The first site has the characteristics of the S cones. Their output combines antagonistically with signals from the L and M cones at a second (blue/yellow opponent) stage. The response nonlinearities were examined by measuring thresholds for a 420‐nm probe presented at the onset of flashed fields of 420‐nm, 520‐nm, and 580‐nm light. Adaptive mechanisms of multiplication and subtraction were identified by presenting probe and flash on steady backgrounds of varying intensity. Adaptation partially restores the sensitivity lost to response compression.
Fast algorithm for computing color gamuts
Authors: Inui Masao
Published: June 2007

A fast and accurate algorithm for computing color gamuts has been developed. In the form presented here for illustration, color gamuts are computed from the dye amounts of subtractive color mixtures. Based on the one‐to‐one correspondence between dye amount space and color space, the simple four‐step algorithm performs a boundary search in dye amount space and a map over to color space. Application to block dyes and commercial reversal film dyes on a desktop computer demonstrates the algorithm's validity, accuracy, applicability, and exceptional speed. © 1993 John Wiley & Sons, Inc.
Measuring the whiteness of human teeth
Authors: García J. A. , Rubiņo M. , Romero J. , Hita E.
Published: June 2007

This work attempts to determine the best index for measuring the whiteness of human teeth. For this the classifications obtained from various whiteness indices have been compared, using Spearman's correlation coefficient, with the responses of 20 observers judging a group of 20 samples of porcelain teeth. The index which gives the best results is that proposed by the CIE, WIC, although the Z% and the CIELAB color difference ΔE are also adequate for measuring the whiteness of human teeth. © 1993 John Wiley & Sons, Inc.
The “alexandrite effect” in gemstones
Authors: Liu Yan , Shigley James , Fritsch Emmanuel , Hemphill Scott
Published: June 2007

The term “alexandrite effect” is used in gemology to describe a distinct change of color appearance when a gemstone is switched from daylight to incandescent light. Gemstones that exhibit the alexandrite effect can actually be divided into four categories based upon the value of the calculated absolute hue‐angle change of the material under different pairs of illuminants. the alexandrite effect is a non‐color‐constancy phenomenon. It can be explained by a combination of both chromaticity adaptations to the different light sources, and vision system responses to the spectral distribution of the light emitted by alexandrite effect gemstones when they are illuminated alternatively by the different light sources.
On the conditions affecting the contribution of color to brightness perception
Authors: Stalmeier Peep F. M. , de Weert Charles M. M.
Published: June 2007

Colored stimuli appear to be brighter than an achromatic stimulus of the same luminance as the colored stimuli. We have studied this effect using similarity judgments in a triadic scaling task. Several instructions and stimulus configurations were used. the color sets contained colors at three luminance levels. When subjects are instructed to attend to brightness differences, the contribution of the brightness axis is strongly increased relative to the contribution of the color channels. Moreover, a correction to the color input is necessary when subjects are instructed to attend to brightness similarities between saturated colors. For a fixed adaptation level, the chromatic input is relatively stronger for the lower luminance levels. This correction is absent in all other investigated conditions. the correction found here confirms an earlier report by Fairchild and Pirotta (1991).
Transferring the 45/0 spectral reflectance factor scale
Authors: Reniff Lisa
Published: June 2007

The accuracy of spectrophotometric measurements is limited by the standards that are used to calibrate the instrument. Therefore, the procedure used in transferring the spectral reflectance factor scale from one material to another for use in calibration must induce the minimum amount of error. the Munsell Color Science Laboratory has been transferring the spectral reflectance factor scale to calibration materials using a statistical method to correct for the most pervasive systematic errors in the measurement process. This method is based on a statistical procedure in which a set of systematic spectrophotometric errors are estimated based on the measurement of seven NIST primary standards and corrected in subsequent measurements. the optimization of the spectral reflectance factor scale to NIST standards minimizes the induced error. the average reflectance factor error consistently found between the corrected measurements of the NIST standards and their certificate values have been 0.0006 and the average δab has been on the order of 0.2.
Appearance [Cesia]: Construction of scales by means of spinning disks
Authors: Caivano Jose Luis
Published: June 2007

The name cesia has been proposed for the aspect of appearance that deals with the sensations aroused by differences in the spatial distribution of light. In a previous article, a system ofcesias was presented. This included u notation system and a solid with three dimensions or variables in which the sensations were organized. The aim ofthis article is to report the development of scales of cesia, constructed with the aid ofrotatory disks holding percentages of materials producing the stimuling for the,five primary sensations of cesia. These primary sensations are: transparence, specular reflection, translucence, difuse reflection, and absorption [black]. Different geometries of observation were needed to evaluate the scales. Numerically, they were built using a power function belween the magnitudes of the sensations and the magnitudes of the stimuli. This research refutes the assumptions that the geometric attributes of appearance cannot be organized in a coordinate system and that synthetic stimuli cannot be produced for these attributes just as they are produced for color by the mixture of three lights. © 1994 John Wiley & Sons, Inc.
Metrology, documentary standards, and color specifications for fluorescent materials
Authors: Billmeyer Fred W.
Published: June 2007

Some aspects of the metrology of fluorescence are reviewed. ASTM Committee E‐12 on Appearance has written two documentary standards on the instrumental measurement of fluorescent colors. Test Method E 1247 provides two procedures for detecting small amounts of fluorescence that might affect the measurement or use of nominally nonfluorescent materials. Practice E 991 deals with the measurement of specimens meant to be viewed under standard natural daylight, and that, therefore, must be illuminated by a good instrument daylight simulator. Two procedures are given for assessing the suitability of the simulator, and the required instrument geometry is specified. A future ASTM standard is under consideration that would describe methods for correcting the data obtained with another instrument source to the data that would have been obtained with standard daylight illumination. Two groups of standard specifications exist for fluorescent colors used for signaling or safety enhancement. One defines suitable chromaticities for both red and orange colors [among others], but ignores the fact that these colors cannot always be obtained with good lightfastness by use of existing pigments. the other group provides instead a red‐orange specification for which specimens with good lightfastness can be obtained. the relative merits of the two groups are discussed.
Problems in measurement of fluorescent materials
Authors: Gundlach Dietrich , Terstiege Heinz
Published: June 2007

Fluorescent materials become increasingly important for signalling and warning purposes. Measurement facilities, however, are still very poor. This article reviews the radiometric aspects of fluorescent materials and the measurement of their radiometric and colorimetric characteristics. the precision of colorimeters and one‐monochromator instruments can be improved by applying luminescent reflectance standards, calibrated with a two‐monochromator system. Problems of radiation feedback with sphere geometry and a way to solve this problem with a two‐monochromator system are discussed.
Simulation of daylight for viewing and measuring color
Authors: McCamy C. S.
Published: June 2007

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.