bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of metameric reflectances
Authors: Worthey James A.
Published: June 2007

Object‐color metamerism becomes visually apparent if two objects match under one light, but not under a second. In the present article, a method is derived by which metameric object colors can be calculated, given the light under which they are to match, and the light under which they are to mismatch. The method gives practical guidance for avoiding or achieving metamerism. The method is not primarily a matter of trial and error and statistics, but depends on a simple calculation that operates on the spectral power distributions of the two lights, along with a set of three color matching functions. The method can deal as well with “observer metamerism,” meaning the effects of observer differences.
The conceptual NCS: An empirical investigation
Authors: Whitfield T. W. A. , Powell A. S. , O'Connor M. , Wiltshire T. J.
Published: June 2007

Two interesting features of the Natural Color System (NCS) are (a) the clear distinction made between the conceptual and atlas versions of the system and (b) the unique status attributed to the conceptual version. The latter finds expression in the claim that the system can be used without reference to atlas samples. In other words, it is claimed that subjects trained in the NCS perform with a high degree of accuracy in colour identification tasks using only their conceptual model for reference. The study reported here is a replication of experiments cited as support for this claim. Subjects were trained in the NCS using NCS training material and carried out colour‐identification tasks. For comparison, a further subject group was trained in the Munsell system and carried out identical tasks. The results indicated (a) a lower level of accuracy than previously reported for those subjects trained in the NCS and (b) little difference in performance between the NCS‐ and Munsell‐trained groups.
The fry uniform chromaticity scale diagram
Authors: Fry Glenn A.
Published: June 2007

In 1945 I created a uniform chromaticity diagram which was a modification of the 1931 CIE Chromaticity Diagram. At that time I tried to relate it to a modulation theory of color vision which has proved to be untenable. In 1965 I switched to a zone theory of color vision which provides a more acceptable physiological basis for my UCS diagram. In the present article I want to explain how the two are related. I make use of three diagrams. The first (my uv diagram) is a color mixture diagram which deals with responses of the cones. The second (my un vn diagram) deals with the yellow‐blue and red‐cyan signals generated in two separate sets of fibers of the optic nerve. It is this independence which permits the relation between u″ and u on the one hand and between v″ and v on the other to be nonlinear. This is my UCS diagram. It yields better uniformity of discrimination steps across the diagram than is possible with a projective diagram. The second diagram is designed to deal with discrimination at the threshold level. The third diagram (my m n diagram) deals with the suprathreshold spacing of the Munsell colors. It is produced by scissoring the two sets of coordinate lines of the u″ v″ diagram around the standard stimulus C. This is related to the way in which signals in the two sets of fibers mix to produce intermediate colors.
An example of a method for correcting radiance data for Bandpass error
Authors: Stearns E. I. , Stearns R. E.
Published: June 2007

As an example of reduction of bandpass errors, a formula is derived for the estimation of zero bandwidth radiance data from radiances measured with a triangular bandpass and a measurement interval equal to the bandwidth.
Physiological causes of individual variations in color‐matching functions
Authors: Nayatani Yoshinobu , Takahama Kotaro , Sobagaki Hiroaki
Published: June 2007

The present study confirms that the individual variations of Stiles' 20 color‐matching functions are physiologically well predicted by those of eye lens and macular optical densities. The principal‐component analysis of the blue color‐matching functions shows the significance of the two independent spectral components, which are expected to correspond to lens and macular optical densities. The lens and the macular densities for each of Stiles' 20 observers are estimated by using their published data physiologically measured. The estimated densities predict well each of Stiles' 20 color‐matching functions. The singular‐value decomposition of the estimated 20 color‐matching functions provides a good estimate of the standard‐deviate observer derived from the original Stiles 20 color‐matching functions by using the same procedure.
Field trials on color appearance of chromatic colors under various light sources
Authors: Nayatani Yoshinobu , Takahama Kotaro , Sobagaki Hiroaki
Published: June 2007

Field trials of the nonlinear color‐appearance model and the nonlinear chromatic‐adaptation transform were done on the effect of chromatic adaptation between illuminants C and A, and also on the visual estimations by Mori and Fuchida under five fluorescent lamps. The model could give reasonably good predictions to the visual estimations in the above two conditions. In addition, the present study confirmed that the nonlinear color‐appearance model and the nonlinear chromatic‐adaptation transform could better predict the chromatic‐adaptation effect between C and A than the von Kries law.
Influence of chroma and hue on spatial balance of color Pairs
Authors: Morriss Robert H. , Dunlap William P.
Published: June 2007

Earlier research has shown that the relative chroma (saturation) of color pairs affects the relative areas of those colors that appear balanced in a predictable way. Small areas of high chroma balance large areas of low chroma. The present study shows that this chroma effect is independent of the background the colors were viewed against, and relatively independent of the hues involved. In particular, the chroma effect is as strong for hue pairs adjacent or intermediate on the color circle as for complementary hues. Finally, this study compared Munsell's theory of spatial balance to that of Moon and Spencer, finding better agreement with the former.
Calibration of a computer controlled color monitor
Authors: Brainard David H.
Published: June 2007

Because of the large number of stimulus configurations that may be displayed on a computer controlled color monitor, direct measurement of the relation between the digital input values to the frame buffer and the output of the monitor is not possible. To calibrate a monitor, it is necessary to make assumptions about the monitor's performance. These assumptions allow the monitor's output for any set of input values to be predicted from the input values and the results of a feasible number of calibration measurements. This article describes a set of assumptions that are sufficient to render the problem of monitor calibration tractable. These are the assumptions of phosphor constancy, phosphor independence, spatial independence, and the single scale factor assumption. If these assumptions hold, a monitor may be calibrated by measurements of the phosphor spectral power distributions, measurements of the phosphor input‐output relations, and measurements of the spatial scale factor at a number of locations. Violations of these assumptions limit the accuracy of calibration. The results of measurements that test the validity of these assumptions for a Barco 5351 monitor are presented.
Colorimetric principles applied to designing test kits for medical diagnosis
Authors: Norrington F. E.
Published: June 2007

Many diseases involve the introduction into the body of highly specific foreign substances (antigens) to which the body responds by producing complementary antibodies. A test method has been developed whereby several different antigens can be detected simultaneously. One drop of fluid (e.g., blood serum, urine, saliva, etc.) from the patient is mixed with one drop of reagent on a card. Within two minutes a colour change takes place, each colour developed being diagnostic of a particular antigen. This paper describes the test and shows how colorimetric methods were used to optimise its performance, standardise the materials used, and determine the requirements for proposed further development.
A novel method for the determination of color matching functions
Authors: Fairchild Mark D.
Published: June 2007

An instrument was developed for the psychophysical measurement of color matching functions. The instrumental design centers around the use of lasers as the primary light sources. The three (RGB) laser beams are independently controlled with acousto‐optic modulators and projected into a diffuser for color mixing. The instrument was designed to allow for free viewing of the matching fields and versatility in the implementation of the matching fields and surround. To simplify data collection, a model was developed that allows the computation of the full spectral tristimulus functions based on just five visual matches. This model expresses color matching functions as linear transforms of the cone action spectra multiplied by variable transmittances of the lens and macula. The model was tested using the 2° color matching data of Stiles and Burch, and preliminary data were collected and modeled using the new instrument.
Hue shifts in unrelated and related colours
Authors: Hunt R. W. G.
Published: June 2007

Published data on the dependence of hue on luminance (the Bezold‐Brücke effect) is analysed in terms of changes of hue angle instead of changes in wavelength so as to assess their visual importance. For unrelated colours, for a given monochromatic wavelength, the changes in hue caused by altering the luminance vary appreciably according to whether the colours are seen side‐by‐side continuously, or side‐by‐side in flashes, or one‐at‐a‐time in flashes. For related colours, for a given chromaticity, the changes in hue caused by changing the luminance factor are examined in the Munsell and NCS systems; although systematic variations occur, they are different in the two systems, and in neither case is there any similarity to the situation for unrelated colours. Changes in illuminance on related colours do not seem to have any systematic effect on hue for a given chromaticity. It is concluded that the Bezold‐Brücke effect for unrelated colours is not relevant when related colours are considered.
Variance‐based color image quantization for frame buffer display
Authors: Wan S. J. , Prusinkiewicz P. , Wong S. K. M.
Published: June 2007

Color image quantization is a process of representing an image with a small number of well selected colors. In this article an algorithm for multidimensional data clustering (termed the variance‐based algorithm), based on the criterion of minimization of the sum‐of‐squared error, is applied to the problem of reducing the number of colors used to represent a given color image. The suitability of the sum‐of‐squared error criterion for measuring the similarity between the original and quantized images is examined using a digitized image and a computer‐generated image. The experimental results indicate that this error measure is basically consistent with the perceived quality of the quantized image. The performance of the variance‐based algorithm is compared with that of other algorithms for color image quantization in terms of quantization images generated using the colors selected by the variance‐based and the mediancut algorithms are also presented.
Historical development of CIE recommended color difference equations
Authors: Robertson A. R.
Published: June 2007

In 1976 the CIE recommended two colour difference formulae, the CIELAB and CIELUV formulae, to promote uniformity of practice pending the development of a better formula. While some of the arguments in favour of the recommendation were political, there were also sound technical reasons for choosing the two formulae. The discussions leading to the recommendation and the reasons that led the CIE to its decision are reviewed. In particular the reasons for the modification of the 1964 (U*, V*, W*) formula to arrive at the CIELUV formula are given, and the derivation of the constants (116, 16, 500 and 200) in the CIELAB formula is explained. Most of the data presented are taken from CIE Committee minutes and correspondence.
Parametric effects on surface color‐difference evaluation at threshold
Authors: Witt Klaus
Published: June 2007

Experiments on thresholds of perceptible color‐difference at CIE color centers have been extended for the parametric effects of the lightness of an achromatic surround and of a separating gap between a pair of painted specimens. Components of perceived color‐difference (hue, chroma, lightness) approximately could be assigned to geometric elements of threshold ellipsoids and used for component analysis. A study of ellipsoid and city‐block modelling revealed ellipsoid to be slightly better. An increase of total threshold by changed lightness of the achromatic surround was found only in the case of the dark CIE Blue, but in every case a gap increased threshold the darker the CIE color center. The results can be used for a correction in color‐difference evaluation.
Categorical color rendering of four common light sources
Authors: Boynton Robert M. , Fargo Lee , Collins Belinda L.
Published: June 2007

Subjects were asked to sort samples from the Optical Society of America (OSA) Uniform Color Scales set into 33 color categories under four separate illuminants: tungsten‐incandescent, metal halide, high‐pressure sodium, and clear mercury. Sorting required that each color sample be designated as a “good,” “acceptable,” or “poor” example within one of the eleven basic color categories specified by Berlin and Kay. Three indices of the categorical color‐rendering capacity of the sources were developed. Assuming tungsten‐incandescent as the reference illuminant, all three measures rated the color‐rendering quality of the tested illuminants from best to worst in the order listed above, in agreement with the CIE color‐rendering index.
European practices and philosophy in industrial colour‐difference evaluation
Authors: McDonald Roderick
Published: June 2007

A survey has been made of the use and methods of Instrumental colour difference measurement in quality control of colour within Europe. Several colour differnce formulae are in use. The performances of the most used formulae, namely CIELAB, CMC, BFD, M&S, and Datacolor, are compared. The degree of implementation of colour difference measurement in the textile, leather, automobile, and coatings industries is summarised. The use of new computer graphics to ensure continuity of colour from batch to batch and the alternative methods of colour sorting to minimise colour differences between batches are described.
Evaluation of a simple method for color monitor recalibration
Authors: Lucassen Marcel P. , Walraven Jan
Published: June 2007

An algorithm for recalibrating a color monitor's RGB input‐output relations is presented that requires only a single measurement of a properly chosen reference stimulus. For the application under concern, i.e., reproduction of 35 different colored patches that were used as stimuli for psychophysical experiments on color constancy, the reference stimulus was a white (D65) presented at a luminance corresponding to the mean of the test stimuli. Three sets of data were obtained for evaluating the algorithm's error reduction power for a given stimulus configuration. These relate to different ways in which the monitor can get out of calibration. That is, slow, but cummulative changes over time, fast changes dur to gun interaction (resulting from changed stimulus conditions), and error introduced by a different setting of the monitor's brightness control. Additional experiments were performed to evaluate the effect of background intensity and color. The algorithm was found to be quite effective in dealing with the instantaneous changes (gun interaction, brightness control), and also for keeping track of the slow changes that may finally necessitate a full recalibration of the monitor.
A colour notation conversion program
Authors: Smith N. S. , Whitfield T. W. A. , Wiltshire T. J.
Published: June 2007

A computer program has been developed that converts between the notations of the Munsell, OSA‐UCS, NCS, DIN, and Coloroid colour order systems and the CIE, CIELAB, and CIELUV colour specification systems. The intention of this article is to outline the development of this program and its structure. Particular attention is given to the accuracy of the program and its associated databases.
Lightness perception of chromatic object colors
Authors: Nayatani Yoshinobu , Umemura Yoshifumi , Sobagaki Hiroaki , Takahama Kotaro , Hashimoto Kenjiro
Published: June 2007

A hypothesis is proposed to predict the perceived lightness of chromatic object colors, which is well known as the Helmholtz‐Kohlrausch effect or the lightness‐reflectance ratio effect (L/Y effect). The hypothesis is, “When two chromatic object colors with different hues have the same values for each of three attributes (whiteness, blackness, and chromaticness), the two colors have the same perceived lightness, including a chromatic‐component contribution.” The hypothesis is tested by two kinds of experiments: perceivedlightness matching using the NCS Color Atlas, and chromatic tiles determined by Wyszecki. Both results strongly confirm the hypothesis. Further, contour lines of constant L/Y ratios are estimated, and are very similar to those reported previously.
Field trials for assessing the method of observer metamerism adopted by CIE
Authors: Nayatani Y. , Tanaka T. , Sobagaki H. , Takahama K. , Hashimoto K.
Published: June 2007

The following field trials are made for assessing the method of observer metamerism adopted by CIE. (1) The individual variation of metameric match was assessed between a fluorescent‐lamp light and each of three different matching stimuli by the CIE method. The high precision of visual color match was confirmed for the 6‐primary Donaldson colorimeter. The prediction was compared with experimental results for a similar fluorescent lamp. (2) The individual variation predicted by the CIE method was compared with that directly derived by using the Stiles original 20 color‐matching functions. The effectiveness of the CIE method was confirmed. (3) It was clarified that the individual variation of colorimetric values on a single test stimulus corresponds to that for the metameric match between the test stimulus and a mixture of the CIE 10° r, g, b primaries. (4) The actual observer variation found by Stiles and Wyszecki in the field trial on the CIE 1964 color‐matching functions was tested using the CIE method. The method is effective to assess the intrusion of other factors in actual color match, in addition to the individual variation of color‐matching functions.
Hue cycle described by graphs and color names
Authors: Pridmore Ralph W.
Published: June 2007

The color appearance of the hue cycle in equal radiance is described in hue, saturation, and brightness/lightness. The latter does not resemble CIE luminance Y (peaking at 555 nm green), but peaks near 570 nm yellow with minor peaks near 490 nm cyan and 530 c magenta. Saturation per watt peaks near 450, 530, 610 nm (blue, green, red). Newton's choice of seven spectrum colors, and particularly his two bluish colors, is explained as major colors rather than merely different hues.
Revised colour‐appearance model for related and unrelated colours
Authors: Hunt R. W. G.
Published: June 2007

To provide a more realistic balance between the relative contributions from cones and rods to the achromatic signal, at various levels of adaptation, revisions have been made to a previously published model of colour vision. Visual areas denoted as the adapting field, the surround, the background, and the proximal field have also been defined. Several minor changes have also been made to make the model more convenient to use. The steps required in using the model are described, and worked examples are included for both related and unrelated colours. For related colours, the differences between the original and revised models are fairly small in the results obtained for samples viewed on grey, or typical average‐scene, backgrounds, at normal photopic levels of illumination, except for lightness and chroma; but for light and dark backgrounds, more wide‐spread changes occur. For unrelated colours, the revised model includes the Bezold‐Brücke dependence of hue on luminance. The predictions given by the model are compared to physiological and psychophysical experimental data.
A system of mesopic photometry
Authors: Trezona P. W.
Published: June 2007

This paper describes a system of photometry designed to make no unjustifiable assumptions, and to have a strong visual linkage. It spans the photopic, mesopic, and scotopic regions and is based on brightness matching a 10‐degree field, centrally fixated. An intensive investigation was made on the trichromator at the National Physical Laboratory, Great Britain, and an extensive one, using a greater number of observers, on the trichromator at the National Research Council, Canada. A bipartite field allowed equal brightness settings of the aperture colour by each of nine observers. The stimuli tested were both spectral and nonspectral and the data were used to derive formulae which a user could employ. From inserting conventional photometric quantities of a stimulus, which might for example be a light source, the user can obtain its corresponding photometric value whether it be photopic, mesopic, or scotopic.
Discrimination ellipsoids of aperture and simulated surface colors by Matching and paired comparison
Authors: Indow T. , Robertson A. R. , Von Grunau M. , Fielder G. H.
Published: June 2007

Discrimination ellipsoids were constructed in the (x, y, Y) space for six colors so: achromatic, red, yellow, green, blue, and brown. the colors were presented on the surround, either dark (aperture color mode) or bright (simulated surface color mode). Ellipsoids were defined by two methods: matching and paired comparison (an extended form of the method of constant stimuli). Hence, four ellipsoids were obtained with so by each of two observers. For simulated surface colors, except for the yellow color, the two methods gave almost the same ellipsoids. Ellipsoids defined by the fluctuation of matches were almost the same for both aperture and simulated surface colors. Those ellipsoids are similar on the chromaticity diagram to ellipses estimated through MacAdam's colormetric coefficients g's. Paired comparisons were more difficult for aperture colors than for simulated surface colors in the sense that the ellipsoids were larger in size. However, the rates of false discrimination for identical pairs (so, so) were higher for surface colors. In spite of the drastic change of appearance of the brown color, no change was observed between the two modes of appearance for ellipsoids obtained by either method. the study is methodological and detailed statistical analyses of the two data processings are included, one based on matchings and the other based on paired comparisons.
Estimation of luminance factor from cie supplementary standard colorimetric observers
Authors: Ohta N.
Published: June 2007

The luminance or luminance factor is not defined in the large viewing field greater than 4° since the color matching function ȳ10(Λ) is not identical to the spectral luminous efficiency V(Λ). the possible errors are estimated when ȳ10 (Λ) is used in place of V(Λ) for evaluating the luminance factor.
Toward a more accurate and extensible colorimetry. Part Ii. Discussion
Authors: Thornton William A.
Published: June 2007

Technical advances in the forty years since the Stiles‐Burch color‐matching work‐among them the bright split‐field visual colorimeter coupled by quartz light pipe to a spectroradiometer‐allow measurement of an accurate absolute spectral power distribution (SPD) of every viewed light. Furthermore, the ability to measure accurately the power‐content of each spectral constituent of a viewed light has clarified both colorimetric procedures and signficance, for example, of color‐matching functions (CMFs) and tristimulus values. Three disparate sets of three spectral primaries were used throughout the work. This has not been done before, and its use elucidated much of the difficulty (as described by Judd, Stiles, MacAdam, Wyszecki, and others) inherent in traditional colorimetry. Errors in computed chromaticities of sets of 28 visually‐matching lights depend strongly on their spectral content, and are particularly large in the presence of high spectral content in the violet, deep red, and near 500 nm or 580 nm. Peaks of visual efficiency, and minima in chromaticity errors, were found with power in three intermediate spectral regions near 450 nm, 530 nm, and 610 nm. Computed luminance (1964 CIE Standard Observer) and power‐content also depend strongly on spectral content of the visually‐matching white lights. That this is true of luminance is generally unknown. Perceived brightness of single spectral lights in isolation, and of mixtures, was examined at length: As a rule, removing one spectral component from a mixture increases perceived brightness, thus invalidating both luminance and R + G + B as correlates of brightness. Visual tests of the Grassmann proportionality and additivity assumptions, with highly metameric mixtures, tended to confirm them. Nevertheless, numerous tests‐substituting pairs of actual visually‐matching lights from one primary‐set for pairs from another, which is how “transformation of primaries” is (mathematically) carried out‐led to the inescapable conclusion that the normal human visual system does not honor such transformation. At the same time, numerous indications supported a particular set of primaries as an invariant of the visual system, making transformation needless as well as invalid. Chromaticity errors are not the fault of the particular maximum‐saturation CMFs utilized; the observer's own CMFs do no better, whatever the primary‐set. Soundness of traditional construction of the chromaticity diagram is shown to depend on the primary‐set, breakdown occurring for some otherwise legitimate primary‐sets.
Estimation equations for practical use on lightness‐reflectance (L/Y) ratios in the whole chromaticity gamut
Authors: Nayatani Yoshinobu , Ihara Masamori , Sobagaki Hiroaki , Hashimoto Kenjiro
Published: June 2007

A multiple regression analysis is reported to predict L/Y ratios as a function of chromaticity coordinates x, y. the specified variables were selected statistically from the 20 terms of Ψmψn. the quantities Ψ, ψ are the transformed values of x, y, respectively, and 1 ≦ m + n ≦ 5. the contour lines of equal L/Y ratios are estimated in the whole chromaticity gamut including spectral colors by using each of the regression equations with 6, 9, and 20 specified variables. the regression equations with 20 specified variables can satisfactorily predict the corresponding experimental results. In case of regression equations with 6 specified variables, the predicted contour lines are significantly different in shape from those of the corresponding experiments. the same defects are found in the Ware‐Cowan equation only using 4 specified variables recommended by CIE Division 1 for further tests.
NCS and DIN notations for the OSA‐UCS atlas samples
Authors: Smith N. S. , Whitfield T. W. A. , Wiltshire T. J.
Published: June 2007

NCS (C/1931) and DIN (C/1931 and D65/1964) notations of the 558 OSA‐UCS atlas samples are presented in two tables. One table provides the NCS and DIN notations for the 424 regular samples; the other for the 134 near‐neutral (half‐step) samples.
Estimation of film thickness nonuniformity effects on coating optical properties
Authors: Bierwagen Gordon P.
Published: June 2007

Film nonuniformities cause many problems for the coating scientist. One area of coating film performance that they impact directly is optical properties. Measurements and predictions of film optical performance are all made assuming uniform film thickness. Incomplete leveling and other film application problems often yield nonuniform films with significant film thickness fluctuations. These film thickness imperfections can be modeled by a sine wave thickness fluctuation, and this fluctuation can be used to estimate the effects of nonuniformity in thickness on optical properties. This has been done using both approximate equations for scattering, transmission, and reflectance in films (zero absorption) and for the Kubelka‐Munk equations including absorption. the effects of average film thickness and amplitude of fluctuation on measured S, R, and T values are predicted numerically for several cases of [K, S] pairs consistent with wavelength independent situations (white or similar films) over black substrates, and then the calculations are used to consider colored films [considering δE(L*a*b*)] over black substrates. Film thickness fluctuations are shown to have considerable impact on film optical properties, especially in thin highly scattering films. Examples of the types of predictions that can be made are given; how the results depend on the coating optical parameters is also shown.
Techniques for simulating object color under changing illuminant conditions on electronic displays
Authors: Troost Jimmy M. , De Weert Charles M. M.
Published: June 2007

We compare several computational schemes that can be used for the simulation of object colors under changing illuminant conditions on electronic displays. These schemes differ in the assumptions that are made concerning illuminant invariant quantities, and the amount of a priori information that is required. This latter feature is especially important for computer graphics applications and theoretical color constancy research because in many instances information about illuminant and object characteristics is minimal. A large set of tristimulus values of Munsell papers, as defined under CIE Standard Illuminant C, served as input data. Next, illuminant invariant quantities were obtained for each computational scheme that were used to predict x, y chromaticity coordinates and relative luminosity Y under nine different phases of daylight, varying from 4000 K to 20000 K. It was found that the differences between so‐called reflectance models on the one hand, and theoretically less accurate tristimulus ratio models on the other, are small and in most cases within three MacAdam units of color difference ≈1 JND).
Color correction using principal components
Authors: Vrhel M. J. , Trussell H. J.
Published: June 2007

The problem of color correction for changes in illumination is briefly reviewed. A new method using the spectral reflectance distribution in the image is introduced and compared to a white‐point mapping method. The new method is based on principal component analysis and thus is dependent upon the characteristics of the images that are to be viewed. These two methods are compared using chromaticity plots and the CIE L*a*b* ΔE measurement, for test samples which include color copiers, thermal writers, ink‐jet printers, and lithography.
Application of some statistical methods for comparing samples of Hue‐Angle data
Authors: Chronicle Endward , Nimmo‐Smith Ian
Published: June 2007

Several color spaces utilize angular measures of hue:for example, CIE 1976 u, v hue‐angle; CIE 1976 a, b hueangle. Such measures are not amenable to conventional statistical analysis, unless a categorization of hue‐angles has previously been decided upon, in which case nonparametric tests are appropriate. In this article we present two recently established methods that are appropriate for the parametric statistical analysis of hue‐angle data from two or more samples: [i] a test of the equality of angular variances; [ii] a test of the equality of mean angles. These tests may be performed easily on a microcomputer and produce statistics conforming approximately to well known distributions. We envisage that the tests will be of interest to psychologists and others working in the field of color research. © 1992 John Wiley & Sons, Inc.
Numerical methods for colorimetric calculations: Sampling density requirements
Authors: Smith Brent , Spiekermann Charles , Sember Robert
Published: June 2007

This article quantifies errors arising from various integration methods and from sampling density in the numerical estimation of colorimetric integrals, e.g., tristimulus values. Both data sampling density and various numerical integration method errors will be distinguished. A test is presented to quantify sampling interval requirements for accurate colorimetric calculations for various illuminants. © 1992 John Wiley & Sons, Inc.
The primary hue circle
Authors: McCamy C. S.
Published: June 2007

Munsell started to base his color‐order system on measured physical quantities, but it came to represent the order of colors us they ure perceived. The hue circle represents fundamental facts about color vision. The Munsell hue circle has anomalous placement of blue and the use ($five principal hues does not relate to color vision nor applied color science. A reoriented hue circle, labeled with the additive and subtractive primariesblue,green, red, yellow, magentu, and cyan‐but retaining the existing Munsell hue spacing and sectors is proposed.The primury hue circle relates to vision and color‐reproduction processes, so it should exert a unifying influence on color .science. 0 1993 John Wi1ey . & Sons. Inc..
Quantifying colour appearance. part III. Supplementary LUTCHI colour appearance data
Authors: Luo M. Ronnier , Gao X. Wang , Rhodes Peter A. , Xin H. John , Clarke Anthony A. , Scrivener Stephen A. R.
Published: June 2007

The experimental data from this study supplements the LUTCHI Colour Appearance Data as described in Part I of this paper. Two further experiments were carried out: one was to check conflicting results found previously, and another was to extend the range of luminance conditions used earlier. In addition, a brightness attribute was added to the original lightness, colourfulness, and hue scales for colour assessment. Experiment I results verified the uncertainties found previously in the comparison between luminous and nonluminous colours, and between the grey background results with and without a white border. Experiment II results revealed the changes in four perceived attributes under six quite different adapting luminances. The results were then used to test five uniform colour spaces and colour‐appearance models used in Part II of this paper. Hunt's 91 model gave more accurate predictions of the experimental visual results, in comparison with the other spaces and models. Its predictive error for all attributes studied is within the accuracy of the typical observer.
Illuminance dependency of equivalent lightness on chromatic object colors
Authors: Nayatani Yoshinobu , Sobagaki Hiroaki , Hashimoto Kenjiro
Published: June 2007

Study of the equivalent lightness of chromatic object colors was reported by Ikeda et al. and Yujiri from the scotopic to the photopic illuminance range. In the photopic range, the results showed the dependence on the adapting illuminance to the Helmholtz‐Kohlrausch effect [the L/Y (lightness/luminance factor) ratio effect]. The model for predicting the perceived lightness of chromatic object colors proposed by the present authors has been modified to take into account the effect of the change of adapting illuminance. By use of the modified model by the present authors and the method for estimation of the equivalent lightness in the mesopic range by Ikeda et al., the equivalent lightness of object colors with five principal Munsell Hues and with various Munsell Chromas were estimated, for comparison with the results observed by Yujiri from 0.02 to 3000 lx.
Surface color and color constancy
Authors: Petrov A. P.
Published: June 2007

Color constancy is often treated as the tendency of surfaces to stay the same perceived color under changing illumination or context (removing/adding/replacing surrounding objects). But these types of color constancies are not basic ones and there is another kind of color constancy that is fundamental for the explanation of all color constancy phenomena. We experience it when looking at a curved uniformly colored surface or when changing the shape of the surface. A new concept of surface color is developed and the variety of all perceived colors is suggested to be described as a nine‐dimensional set of 3 X 3 matrices corresponding to different surface colors. Examples of color matrices calculated for some colored surfaces being viewed by the standard viewer are presented and arguments supporting the concept are discussed. It is shown that the set of color matrices represents all perceived colors quite adequately.
CRT colorimetry. part I: Theory and practice
Authors: Berns Roy S. , Motta Ricardo J. , Gorzynski Mark E.
Published: June 2007

The relationship was derived for computer‐controlled color CRT displays between spectral radiant exitance emitted and digital counts. The derivation was historical and could be traced to pioneering work in photographic sensitometry, vacuum tube physics, and broadcast television. By performing radiometric measurements relative to a display's maximum exitance, the model simplified to a two‐stage model. The first stage was a nonlinear transformation relating normalized digital‐to‐analog converter values to device‐dependent monitor tristimulus values using model parameters of gain, offset, and γ. The second stage was a linear transformation where the device‐dependent monitor tristimulus values were transformed to device‐independent CIE tristimulus values. By using the model, colorimetric characterization accuracy of better than 0.5 CIELAB color‐difference units for 125 colors sampling the display color gamut was achieved by measuring the CIE tristimulus values of only eight colors. The model had equivalent performance to methods using extensive measurements and table lookup. © 1993 John Wiley & Sons, Inc.
Age‐related changes in the color appearance of broadband surfaces
Authors: Schefrin Brooke E. , Werner John S.
Published: June 2007

Chromatic and achromatic components of 15 broadband surfaces were scaled by 15 younger (mean age = 21.3 yrs) and 15 older (mean age = 71.9 yrs) subjects. Colored surfaces were obtained from the OSA Uniform Color Scales and presented as 2°‐diameter test stimuli that were freely viewed. Stimuli were presented in a grey (L = 0) ganzfeld‐like hemisphere with an illuminant having a correlated color temperature of 6200 K. Five stimuli were presented at three lightness levels (L = −4, 0 and +4). Each lightness level included samples chosen so that one pair plotted approximately along a tritan axis in MacLeod‐Boynton receptor‐excitation space and another pair plotted on an axis of constant S‐cone stimulation. The appearance of each test stimulus was scaled using the hue terms red, green, yellow and blue, and in terms of the proportion of overall chromatic content. The results indicate that hue names were used similarly for the two groups of subjects, however, older subjects perceived all stimuli as having less chromatic content than demonstrated by younger observers. Differences between the two age groups in perceived chromatic content of the test stimuli progressively increased as the lightness and luminance levels of the test stimuli decreased. Results obtained from control experiments suggest that this difference between the two age groups is not due to the influence of senile miosis or lenticular senescence leading to variations in the illuminances and spectral compositions of the test lights reaching the retina. © 1993 John Wiley & Sons, Inc.
Spatial integration properties in vision with chromatic stimuli
Authors: Kawabata Yasuhiro
Published: June 2007

The present study showed that (1) the critical area of spatial integration was larger for equiluminous chromatic stimuli than for luminance stimuli, and that (2) the critical area became smaller as the chromatic saturation of the adaptation field was increased. The latter suggests that the chromatic coding systems, which are assumed to posses poorer spatial resolution or larger spatial integration than the luminance system, could change their spatial integrating organization independently of the luminance system which could also change its own spatial organization. © 1993 John Wiley & Sons, Inc.
Successive‐ganzfeld haploscopic viewing technique for color‐appearance research
Authors: Fairchild Mark D. , Pirrotta Elizabeth , Kim Taek
Published: June 2007

A new experimental technique for color appearance research is described. This technique, successive‐Ganzfeld haploscopic viewing, combines advantages of traditional haploscopic and successive‐haploscopic techniques with modifications that provide a more amenable viewing situation for the observer. This note reviews the need for haploscopic viewing techniques in color appearance research and the pros and cons of traditional techniques. and outlines the implementation of the new technique along with current and potential applications.
Existence of two kinds of representations of the helmholtz‐kohlrausch effect. I. the experimental confirmation
Authors: Nayatani Yoshinobu , Sobagaki Hiroaki , Hashimoto Kenjiro
Published: June 2007

In the representation of the Helmholtz‐Kohlrausch effect, a new method (the VCC method using variable chromatic colors) is proposed in addition to the method used so far (the VAC method using variable achromatic colors). The new VCC method showed a significantly larger Helmholtz‐Kohlrausch effect than the VAC method previously used. For practical applications, the results by the VCC method are more effective than the VAC method. Three kinds of experiments are reported for clarifying the difference in effect between the two methods. © 1994 John Wiley & Sons, Inc.
Existence of two kinds of representations of the helmholtz‐kohlrausch effect. II. the models
Authors: Nayatani Yoshinobu , Sobagaki Hiroaki , Hashimoto Kenjiro
Published: June 2007

A formulation for predicting the Helmholtz‐Kohlrausch (H‐K) effect is given to the new VCC (variable chromatic color) method, which can derive the luminance factors of various chromatic object colors that match in perceived lightness with a fixed achromatic color. By using the formulation, the H‐K effect by the VCC method is predicted within the whole chromaticity gamut including spectral colors. the magnitude of the effect in logarithmic scale by the VCC method is estimated to be twice as large as that by the VAC (variable achromatic color) method previously used. It is also stated that the VCC method is practically more important than the VAC method. the effectiveness of the new formulation is confirmed by comparing its predictions with the observations in two kinds of experiments. © 1994 John Wiley & Sons. Inc.
Some reflections on studying colour combinations
Authors: Sivik Lars , Hård Anders
Published: June 2007

This article opens with a critical discussion of “laws of colour harmony,” which is followed by an examination of the diverse theoretical and empirical foundations for the relatively common concept “complementary colours.” Using the perceptual NCS‐system for colour description as a basis, the authors have outlined a colour combination model, which is described briefly here. © 1994 John Wiley & Sons, Inc.
Luminescent pigments in security applications
Authors: Becidyan A. Nurhan
Published: June 2007

Papers and any printable surface that have value are subject to forgeries. Various methods of security printing are identified and utilizing luminescent pigments as security items are discussed. Problems with classical luminescent pigments because of toxicity and particle size are identified. A new range of luminescent pigments that are either excited by UV or IR are presented and their chemical and physical characteristics defined. Also samples from actual security applications are given. © 1995 John Wiley & Sons. Inc.
Colorimetric evaluation of daylight simulator sources
Authors: Hisdal Bjarne
Published: June 2007

The color shift of a sample due to a change in illuminant can be expressed either in terms of the CIE General Color Rendering Index, Ra, based on the average for eight color samples, or in terms of the CIE Metamerism Index MIvis, the average for five pairs (or couples) of samples. It is shown that, in an ideal case where the eight samples constitute four complementary pairs, the value of the average for eight can be predicted accurately from the average for only four of the eight samples. This is approximately also the case for a prediction based on four of the actual eight CIE samples, but in this case there is some uncertainty in the predicted Ra values. For MIvis, a useful approximation in value can be obtained using only two of the five defined couples. Finally, it is shown that Ra and MIvis evaluate illuminants in largely the same way.
Sensitivity differences in Chroma, Hue, and Lightness from several classical threshold datasets
Authors: Melgosa M. , Hita E. , Pérez M. M. , El Moraghi A.
Published: June 2007

A check of the weighting functions proposed by the CIE Technical Committee 1‐29 (TC1‐29) [Color Res. Appl. 18, 137–139 (1993)] has been carried out using pairs of samples with only a threshold difference in chroma, hue, or lightness. Experimental results with object and aperture colors were used and some parametric factors can be appointed: the dependence of ΔC* on C* appears to be about two times stronger for related color versus the aperture color mode; and the ΔH* dependence on C*, weak but significant for related colors, becomes insignificant for aperture colors. the hue‐angle dependences of ΔH* after correction for C* and the dependences of ΔL* on L* or C* are found not significant for aperture colors. After normalization of the five different datasets employed, the results achieved are in overall good agreement and support the proposal of the CIE TC1‐29.
Determination of constant Hue Loci for a CRT gamut and their predictions using color appearance spaces
Authors: Hung Po‐Chieh , Berns Roy S.
Published: June 2007

A colorimetrically characterized computer‐controlled CRT display was used to determine 24 loci of constant perceived hue for pseudo‐object related stimuli, sampling the display's interior color gamut at constant lightness and the edge of its gamut at variable lightness. Nine observers performed three replications generating matching data at 132 positions. the constant hue loci were used to evaluate the correlation between perceived hue and hue angle of CIELAB, CIELUV, Hunt, and Nayatani color appearance spaces. the CIELAB, CIELUV, and Hunt spaces exhibited large errors in the region of the blue CRT primary, while the Nayatani and CIELUV spaces produced large errors in the region of the red primary for constant lightness stimuli. Along the edge of the CRT's color gamut (variable lightness stimuli), all the spaces had a similar trend, large errors in the cyan region. the differences in performance between the four spaces were not statistically significant for the constant lightness stimuli. For the variable lightness stimuli, CIELAB and CIELUV had statistically superior performance in comparison with the Nayatani space and equal performance in comparison with the Hunt space. It was concluded that for imaging applications, a new color appearance space needs to be developed that will produce small hue error artifacts when used for gamut mapping along loci of constant hue angle. © 1995 John Wiley & Sons, Inc.