Showing papers in "Color Research and Application in 2005"
TL;DR: This article indicates several potential implementation errors that are not uncovered in tests performed using the original sample data published with the recently developed CIEDE2000 color-difference formula.
Abstract: This article and the associated data and programs provided with it are intended to assist color engineers and scientists in correctly implementing the recently developed CIEDE2000 color-difference formula. We indicate several potential implementation errors that are not uncovered in tests performed using the original sample data published with the standard. A supplemental set of data is provided for comprehensive testing of implementations. The test data, Microsoft Excel spreadsheets, and MATLAB scripts for evaluating the CIEDE2000 color difference are made available at the first author's website. Finally, we also point out small mathematical discontinuities in the formula. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 21–30, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20070
1,451 citations
TL;DR: The purpose of this publication is to describe PCA and present examples in its use for colorant estimation, spectral data reduction, and defining multidimensional confidence regions for colorimetric scatter data.
Abstract: Principal component analysis, abbreviated PCA, has been an important and useful mathematical tool in color technology since the 1960s. Its uses have included defining tolerance intervals and ellipsoidal regions, estimating colorant spectral properties from mixtures, deriving CIE daylight, data reduction for large ensembles of spectra, and spectral imaging. Although PCA is a common topic in many engineering disciplines, statistics, and mathematics, many color-technology professionals and color-science students come from disciplines where this technique is not part of their curricula. It is from this perspective that this review publication was written. The purpose of this publication is to describe PCA and present examples in its use for colorant estimation, spectral data reduction, and defining multidimensional confidence regions for colorimetric scatter data. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 84–98, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20086
240 citations
206 citations
TL;DR: In this article, the effects of fiber added to yogurt during fermentation and cold storage were studied, and overall composition, pH, acidity, syneresis, L*, a*, and b* values were determined.
Abstract: Orange fiber obtained from orange juice by-products was added to yogurt. Fiber (0%, 0.6%, 0.8%, and 1% doses and different fiber size: 0.417–0.701 and 0.701–0.991 mm) effects on color during yogurt fermentation and cold storage were studied. Overall composition, pH, acidity, syneresis, L*, a*, and b* values were determined. Sensory evaluation of yogurts was carried out. Fiber addition did not cause changes in yogurt acidification and color during fermentation process, though decreased L* value and increased b* value of the milk. Color evaluation along fermentation is pH dependent (R > 0.870). pH decreased and syneresis increased along cold storage. Because of the acidification process, L* value decreased and a* and b* values increased in all yogurts. Yogurts with 1% fiber were significantly different from the others along cold storage, presenting lower L*, higher a* and b* values, and lower syneresis. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 457–463, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20158
126 citations
TL;DR: The CIELAB color space was found to perform at least as good as or better than the other color spaces tested, and the ability to predict image similarity increased with the number of bins used in the histograms, for up to 512 bins (8 per channel).
Abstract: Colour is the most widely used attribute in image retrieval and object recognition. A technique known as histogram intersection has been widely studied and is con- sidered to be effective for color-image indexing. The key issue of this algorithm is the selection of an appropriate color space and optimal quantization of the selected color space. The goal of this article is to measure the model performance in predicting human judgment in similarity measurement for various images, to explore the capability of the model with a wide set of color spaces, and to find the optimal quantization of the selected color spaces. Six color spaces and twelve quantization levels are involved in eval- uating the performance of histogram intersection. The cat- egorical judgment and rank order experiments were con- ducted to measure image similarity. The CIELAB color space was found to perform at least as good as or better than the other color spaces tested, and the ability to predict image similarity increased with the number of bins used in the histograms, for up to 512 bins (8 per channel). With more than 512 bins, further improvement was negligible for the image datasets used in this study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 265-274, 2005; Published online in Wiley Inter-
71 citations
Journal Article•
71 citations
TL;DR: In this article, the authors show how the simple words can maximize how the impression of this book is uttered directly for the readers, even if they have known about the content of measurement of sensation so much, they can easily do it for better connection.
Abstract: Every word to utter from the writer involves the element of this life. The writer really shows how the simple words can maximize how the impression of this book is uttered directly for the readers. Even you have known about the content of measurement of sensation so much, you can easily do it for your better connection. In delivering the presence of the book concept, you can find out the boo site here.
67 citations
TL;DR: The texture effect on visual colour difference evaluation was investigated in this article, where five colour cen- ters were selected and textured colour pairs were generated using scanned textile woven fabrics and colour-mapping technique.
Abstract: The texture effect on visual colour difference evaluation was investigated in this study. Five colour cen- ters were selected and textured colour pairs were generated using scanned textile woven fabrics and colour-mapping technique. The textured and solid colour pairs were then displayed on a characterized cathode ray tube (CRT) mon- itor for colour difference evaluation. The colour difference values for the pairs with texture patterns are equal to 5.0 CIELAB units in lightness direction. The texture level was represented by the half-width of histogram, which is called texture strength in this study. High correlation was found between texture strength and visual colour difference for textured colour pairs, which indicates that an increasing of 10 units of texture strength in luminance would cause a decreasing of 0.25 units visual difference for the five colour centers. The ratio of visual difference between textured and solid colour pairs also indicates a high parametric effect of texture. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 341-347, 2005; Published online in Wiley InterScience (www.interscience.wiley.
52 citations
TL;DR: In this article, the authors compared visual results to four color-difference equations, CIELAB, CMC, CIE94, and CIEDE2000, and found that CMC most closely represented judgments of average observers.
Abstract: Ninety-six nylon pairs were prepared, including red, yellow, green, and blue standards, each at two lightness levels with CIE94 ΔE units ranging from 0.15 to 4.01. Visual assessments of acceptability were carried out by 21 females. Logistic regression compared visual results to four color-difference equations, CIELAB, CMC, CIE94, and CIEDE2000. It was found that CMC most closely represented judgments of average observers. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 288–294, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20124
42 citations
TL;DR: Visual evaluation experiments of color discrimination threshold and suprathreshold color-difference comparison were carried out using CRT colors based on the psychophysical methods of interleaved staircase and constant stimuli to report the reproducibility of this kind of experiment usingCRT colors and the variations between CRT and surface data.
Abstract: Visual evaluation experiments of color discrimination threshold and suprathreshold color-difference comparison were carried out using CRT colors based on the psychophysical methods of interleaved staircase and constant stimuli, respectively. A large set of experimental data was generated ranged from threshold to large suprathreshold color difference at the five CIE color centers. The visual data were analyzed in detail for every observer at each visual scale to show the effect of color-difference magnitude on the observer precision. The chromaticity ellipses from this study were compared with four previous published data, of CRT colors by Cui and Luo, and of surface colors by RIT-DuPont, Cheung and Rigg, and Guan and Luo, to report the reproducibility of this kind of experiment using CRT colors and the variations between CRT and surface data, respectively. The present threshold data were also compared against the different suprathreshold data to show the effect of color-difference scales. The visual results were further used to test the three advance color-difference formulae, CMC, CIE94, and CIEDE2000, together with the basic CIELAB equation. In their original forms or with optimized KL values, the CIEDE2000 outperformed others, followed by CMC, and with the CIELAB and CIE94 the poorest for predicting the combined dataset of all color centers in the present study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 198–208, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20106
33 citations
TL;DR: In this paper, a survey of Roman paintings in two rooms in a villa at El Ruedo (Almedinilla, Cordoba, Spain) is presented, where different techniques and procedures, such as X-ray diffraction and diffuse reflectance, are used to identify the pigments.
Abstract: In the present survey, we have analyzed Roman paintings in two rooms in a villa at El Ruedo (Almedinilla, Cordoba, Spain). We used different techniques and procedures, such as X-ray diffraction and diffuse reflectance. We established parameters that define colours in every international system. The diffuse reflectance techniques allowed us to identify the pigments, emphasizing that their mixtures are usually based upon a single chromatic pigment. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 448–456, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.
TL;DR: Balasubramanian et al. as mentioned in this paper proposed a 3D look up table (LUT) based color characterization model for the case of an end user who has no direct knowledge of the internal properties of the display device or its device driver.
Abstract: The primary goal of a color characterization model is to establish a mapping from digital input values di (i = R,G,B) to tristimulus values such as XYZ. A good characterization model should be fast, use a small amount of data, and allow for backward mapping from tristimulus to di. The characterization models considered here are for the case of an end user who has no direct knowledge of the internal properties of the display device or its device driver. Three characterization models tested on seven different display devices are presented. The characterization models implemented in this study are a 3D look up table (LUT) (Raja Balasubramanian, Reducing the Cost of Lookup Table Based Color Transformations, Proc IST44:321–327), a linear model (Fairchild MD, Wyble DR. Colorimetric Characterization of the Apple Studio Display (Flat Panel LCD). Munsell Color Science Laboratory Technical Report, 1998), and the masking model (Tamura N, Tsumura N, Miyake. Masking Model for accurate colorimetric characterization of LCD. Proc IST312–316). The devices include two CRT monitors, three LCD monitors, and two LCD projectors. The results of this study indicate that a simple linear model is the most effective and efficient for all devices used in the study. A simple extension to the linear model is presented, and it is demonstrated that this extension improves white prediction without causing significant errors for other colors. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 438–447, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.
TL;DR: In this article, the effect of luminance on ellipse area, axis dimensions (a and b), and a/b ratio on chromaticity discrimination was quantified using four data sets.
Abstract: Four data sets are analyzed to quantify three effects of luminance of samples on chromaticity discrimination: on ellipse area, axis dimensions (a and b), and a/b ratio. Ellipses for aperture, surface, and simulated surface colors in CIE 1931 and 1964 x, y, Y color spaces are shown to reduce axis dimensions with higher luminance by different functions for the major and minor axes. Reduction is greater for major than minor axes, thus improving ellipse circularity. The functions plot straight lines in log-log scale as power law equations, except luminances below 3 cd/m2. We give formulae to predict a and b axes, a/b ratio, and ellipse area for almost any luminance in x, y, Y spaces. Effect of luminance is remarkable on ellipse area, which on average halves with every 3.5 times higher luminance. To illustrate the substantial effects of luminance, RIT-DuPont ellipses are predicted for three levels of equal luminance at 42, 212, and 2120 cd/m2. In the latter, ellipses are much smaller and are nearer circular than in the former. Higher luminance is known to improve color discrimination, so reduced ellipse area is to be expected but does not occur in CIELAB and DIN99 spaces because of lack of luminance-level dependency. We discuss our results' implications on uniform color space. Weber fraction ΔY/Y indicates brightness discrimination decreases with increasing luminance and is thus independent of chromaticity discrimination. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 186–197, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20107
TL;DR: In this paper, the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°.
Abstract: It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125
TL;DR: In this article, the robustness of the forward and reverse modes of the CIECAM-021 color appearance model has been evaluated in the CIE TC8-01.2 standard.
Abstract: CIE TC8-01 has adopted a new color appearance model: CIECAM021 replaces the CIECAM97s.2 The new model consists of a number of refinements and simplifications of the CIECAM97s color appearance model. This article describes further tests to the robustness of the forward and reverse modes.
TL;DR: In this article, the usefulness and importance of chromatic tone concept on object colors is discussed. But the authors focus on the effect of tone on perceived lightness and degree of vividness.
Abstract: The present study describes the usefulness and importance of chromatic tone concept on object colors. It is clarified that the concept of a tone category consists of the same perceived lightness and the same degree of vividness of chromatic object colors in the tone irrespective of hue. Prediction equations are given to color attributes on perceived lightness and degree of vividness. They clearly show different functions on metric lightness and metric chroma on the two color attributes. It is also clarified that the theoretical opponent-colors system by the author (NT system) gives a basis for defining the tone concept, perceived lightness, and degree of vividness. The results of the present study are useful for understanding fundamental color notion “tone,” which is important both in the fields of colorimetry (fundamental color-perception study) and color design (practical application). In addition, attributes of equivalent whiteness–blackness [W-Bk]eq and equivalent chroma Ceq are proposed. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 221–234, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20108
TL;DR: Chromatic adaptation transforms (CATs) have appeared in different forms and the reasons for these forms, and the relationships between them, are described.
Abstract: Chromatic adaptation transforms (CATs) have appeared in different forms. The reasons for these forms, and the relationships between them, are described. The factors governing which type of CAT should be used in different applications are explained. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 69–71, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20085
TL;DR: Significant differences in color coordinates were found between retail displays that mounted identical fluorescent models, proving the important role of uncontrolled environmental factors like daylight or scattered light from the walls and ceiling.
Abstract: The color of beef longissimus dorsi muscle of a homogeneous group of fifteen males of Pirenaica breed in terms of the CIELAB color space was studied using the actual illuminating conditions existing in a representative fraction of retail displays operating in 51 local butcher's shops and supermarkets. All retail displays mounted fluorescent lamps and up to nine fluorescent models with different chromatic characteristics were found. Meat color was analyzed at four different times: immediately after cutting and after 1 day, 5 days, and 7 days of exposure to air. At each measurement day computed a*, b*, C* and hab color coordinates gave significantly higher values than the corresponding D65 values. All fluorescent models enhanced the red color of meat but none of them masked or enhanced meat color differences between samples or between measurement days. Significant differences in color coordinates were found between retail displays that mounted identical fluorescent models, proving the important role of uncontrolled environmental factors like daylight or scattered light from the walls and ceiling. With respect to computed color coordinates, the intrinsic natural variations in the color of meat samples were more important than variations in the illuminating conditions. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 304–311, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20123
TL;DR: The Relative Absorption Model introduced here is an explicit neural network that generates neural correlates of color vision, and makes detailed predictions of known color and neural phenomena, including familiar aspects of color perception.
Abstract: Opponent processing is widely accepted as providing a general framework for the standard model of human color vision. After the cones' responses are transmitted to second stage neurons, however, there is no consensus on exactly how synaptic connections are organized. The Relative Absorption Model introduced here is an explicit neural network that generates neural correlates of color vision. The model makes detailed predictions of known color and neural phenomena, including familiar aspects of color perception. Until now these phenomena have not had an explicit neural explanation. The model's simplicity shows that color does not require complex processing of spectral information. The network receives excitatory and inhibitory input from three classes of spatially proximate photoreceptors with different spectral sensitivities. Four second stage neurons provide symmetric input to four third stage neurons, whose outputs are correlates of red, green, blue, and yellow. These color cells identify which receptor type has the greatest absorption of photons and which has the least. Their response intensities correspond to the differences between those absorptions and the middle absorption. A single second stage neuron computes violet and purple information that is then transmitted through the red and blue channels, the only channels in the network capable of conveying the information. Five additional neurons produce correlates of black and white. The white cell's response intensity measures the smallest of the three absorptions, and the black response measures how far the largest absorption is from full saturation. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 252–264, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20121
TL;DR: In this article, a total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively, each combination was assessed by nine observers using a matching technique.
Abstract: The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074
TL;DR: In this article, a comparison of three color order systems (Munsell, NCS, and Nayatani Theoretical) is made, and the importance of chromatic strength function is clarified in the comparison.
Abstract: Two kinds of color order systems—Type I (Munsell system, its representative) and Type II (Swedish Natural Colour System (NCS), its representative)—are widely used for systematic ordering of object colors. The reasons are clarified why two kinds of systems are necessary. The reasons are (1)the problem caused by the use of the present CIE photometric and colorimetric system and (2)the neglection of chromatic strength (CS) of each hue to perceived color attributes. In addition, a comparison is made between NCS and Nayatani Theoretical (NT) systems, which are in the same category of color order system–Type II. The importance of CS function is clarified in the comparison of the three color order systems studied. Special features of the three color order systems (Munsell, NCS, and NT) are described in detail. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 295–303, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20127
TL;DR: A corollary of Grassman's linearity law is formally derived, and states: if a number of colors have a corresponding color appearance A in different illuminants, then their complementary colors have the same color appearance B.
Abstract: A corollary of Grassman's linearity law is formally derived, and states: If a number of colors have a corresponding color appearance A in different illuminants, then their complementary colors have a corresponding color appearance B. The informal logic is that: (1) a perceived color has only one complementary color; (2) two or more corresponding colors have the same complementary color (given the illuminant whites are a color match); so (3) the complementary colors to corresponding colors will themselves be a set of corresponding colors. A method of predicting corresponding colors is derived theoretically and shown to agree with data. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 371–381, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.
TL;DR: General hypothesis for the definition of chromatic-opponency functions are given in a black-box approach to the problem and a performance of these hypothesis is successfully realized on the OSA-UCS system, for extra macula vision, and on the chromatic discrimination ellipses, for macular vision.
Abstract: General hypothesis for the definition of chromatic-opponency functions are given in a black-box approach to the problem. It is supposed that the color signals in the visual color processing can be factorized into the product of the lightness times a pair of chromatic opponency functions and the whole chromatic processing consists of three independent processes: a linear transformation, a logarithmic compression, and a chromatic opponency actuation. The main chromatic opponency functions, obtainable by very general hypothesis on the symmetry and on the homogeneity degree, are supposed equal to the logarithms of tristimulus-value ratios in a proper reference frame of the tristimulus space. The perceptual chromatic functions, individually with uniform scales, are a linear mixing of the main chromatic opponency functions. The Bezold–Brucke hue shift is not considered. A performance of these hypothesis is successfully realized on the OSA-UCS system, for extra macula vision, and on the chromatic discrimination ellipses, for macular vision. Unique hues are derived from the main chromatic opponency functions of spectral lights. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 31–41, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20072
TL;DR: The investigation of the effects of surrounding brightness on a visual search for three safety colors: red, orange, and yellow implies that the recognition of orange tends to be influenced by the surrounding brightness.
Abstract: The present article reports the investigation of the effects of surrounding brightness on a visual search for three safety colors: red, orange, and yellow. Images of visual stimuli consisting of an array of colored circles placed on a large visual field (a visual angle of 40°) were displayed on an 80-in. screen with a DLP projector. Experiment I examined the search efficiency under three levels of background luminance that were equivalent to the three target luminances. The results showed that the search efficiency for the orange target decreased as the number of distractors increased, under each of the background luminance levels, whereas the efficiency scarcely decreased for the red and yellow targets. Although a reduction in background luminance increased the search efficiency for the orange target, it is suggested that the effect of background luminance is smaller than the effect of the target color in search efficiency. Experiment II examined the search efficiency under three conditions of low levels of incident illuminance, which were matched with a linear regression to the luminance of color chips of safety colors measured twilight conditions. The results showed that the search efficiency for the orange target decreased as the number of distractors increased under each of the different illuminance conditions, whereas the efficiency scarcely decreased for red and yellow targets. Furthermore, as illuminance decreased, the search time for the orange target was more greatly impacted than for red or yellow. These results imply that the recognition of orange tends to be influenced by the surrounding brightness. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 400–409, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20152
TL;DR: In this article, the authors examined changes in Australian residential interior colours over the twentieth century and found that the main variation during the century was in the hue dimension, whereas the variation in each of the NCS colour dimensions was greater in the second half of the century.
Abstract: A question that has received remarkably little empirical attention is whether colour trends reflect the prevailing sociocultural lifestyle conditions of a society. This is exemplified by such assertions as “the austerity of the War years was accompanied by sombre colours.” The presumed existence of order to colour consumption and a causal association between it and sociocultural lifestyle conditions provides the theoretical underpinnings to the work of colour forecasting agencies. The present study investigated this question by examining changes in Australian residential interior colours over the twentieth century. Colour palettes were assembled decade by decade and an analysis was undertaken using the NCS system. The results indicate that the main variation during the century was in the hue dimension. However, variation in each of the NCS colour dimensions was greater in the second half of the century. No evidence was found to support the notion of colour cycles or any tangible order to colour consumption. Although some colour palettes could be partially accounted for by developments in colour/materials technology, such influences were short-lived. The picture that emerges does not support the notion that future colour trends can be predicted on the basis of past colour trends. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 235–242, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col. 20110
TL;DR: Werner Spillmann as discussed by the authors is known as a colour consultant, influential pedagogue, and passionate promoter of colour as a primary design issue, and has successfully introduced color as a basic element of architectural education and also developed a method for using colour in environmental design.
Abstract: Werner Spillmann is known as a colour consultant, influential pedagogue, and passionate promoter of colour as a primary design issue. This article aims to present Spillmann's important contribution to environmental colour design giving special attention to his noteworthy activities in the context of the International Colour Association (AIC). Since 1960, beginning with the period when he became a lecturer and subsequently professor in the Department of Architecture at the Winterthur Polytechnic in Switzerland, Spillmann has successfully introduced colour as a basic element of architectural education and also developed a method for using colour in environmental design. During the initial years of the AIC, Spillmann attended the association's rather sporadic events beginning with its first Congress in 1969. Spillmann's influence on the AIC grew with the association's own consolidation and increasing international importance. He presented his first AIC paper in 1976 and by 1977, when the AIC began to consequently fulfill its constitutional aim of realizing an annual program and had become an internationally renowned organization in the field of colour studies, Spillmann began to play a key role in the leadership of the association. In 1982, Spillmann became a member of the AIC Study Group on Environmental Colour Design. In 1983, he was invited to give a presentation at the AIC Midterm Meeting in Sweden, and, in 1985, he was elected to the AIC Executive Committee for the period 1986–1989. In serving the AIC during this time period, he organized the Interim Meeting on Colour in Environmental Design, which took place in 1988 at the Winterthur Polytechnic. Spillmann's contribution to the AIC represents the crystalization of the theoretical and practical lines of development that he pursued through his own teaching and professional design practice. During this same time period that he was intensely involved in the AIC, his importance and influence as a teacher and design professional increased as well. The intense courses he developed for architects, designers, and planners and taught in Winterthur between 1982 and 1995 were highly successful. As a teacher, Spillmann was acclaimed not only because of his consistent methodological approach and comprehensive content of his courses but especially for his charisma. Spillmann's involvement in the AIC and his teaching and personal professional development demonstrate how his assiduous striving toward a greater appreciation of colour as an imminent element in contemporary architectural design resulted in raising awareness of the psychological, social, and cultural value of colour within the related fields of architectural history and theory, cultural studies, design, and urbanism. Especially Spillmann's special contribution is underscored by his capacity to take up new approaches adapting and testing these through application in architectural education and design practice. Spillmann has published several essays on colour in environmental design and colour order systems. He presently lives in Basel, Switzerland. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 53–65, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20075
TL;DR: In this article, the convergence of the Hawkyard method is examined and the necessary and sufficient condition to achieve convergence, using the method, is given, and the method is then modified to make it an analytical method.
Abstract: An iterative method was developed by Hawkyard in 1993 for generating reflectance functions, based on a given set of tristimulus values. In a recent article by Dupont (Col Res Appl 2002;27:88-99), many methods for generating reflectance functions were compared, and it was shown that the Hawkyard method is one of the best methods. However, one of the weak points of the Hawkyard method is its iterative nature. In addition, one important issue for the Hawkyard method is its convergence, which has not been addressed. In this article, this issue is examined. The necessary and sufficient condition to achieve convergence, using the Hawkyard method, is given. The method is then modified to make it an analytical method.