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Color Research & Application

Wiley Online Library : Color Research & Application

Published: 2017-10-01T00:00:00-05:00


Application of the nondestructive second derivative spectrophotometry to eliminate the effect of substrate in identification of madder used in Persian carpets


The handmade Persian carpet is famous worldwide not only for its elegant design and artistic structure, but also for its brilliant color harmony and incomparable raw materials. Various natural dyes accompanied by different mordants are used on various woolen yarns to obtain a wide range of unrepeatable shades for carpet. In this article, as a first step, the diversity of the undyed woolen yarns used in Persian carpets was statistically investigated by implementation of the Principle Component Analysis. Then the second derivative of Kubelka-Munk function of samples dyed with madder was considered to reach a pattern for identifying madder. The results show that, although the spectral reflectance of different selected woolen yarns has at least 3 dimensions, all derivative curves are qualitatively very similar with the same minimum and maximum peaks at 510 and 605 nm, respectively. The findings are confirmed when various types of madder were used in the dyeing process. As a result, it is shown that the nondestructive derivative spectrophotometry is able to identify madder on alum mordanted woolen yarns used in Persian carpets and to eliminate the effect of substrate. It is a useful technique for preservation, conservation, and dissemination of the Persian carpet.

Handling translucent specimens in an opaque Kubelka–Munk Environment


Computer-color matching usually employs a subset of Kubelka–Munk equations which require that each specimen analyzed be at complete hiding. This set of equations is preferred because they are simpler than their counterpart equations that operate at incomplete hiding. On the other hand, in coatings and plastics very often colorant specimens must be utilized that, either because of their nature or concentration, fail to qualify as being at complete hiding. This communication examines techniques for handling such cases and makes recommendations for obtaining the theoretical opaque reflectance of the specimens from measurements over both black and white. In addition, the article recommends a new relationship that more aptly characterizes the contrast ratios required than previous methods have done.

Cognitive performance and emotion are indifferent to ambient color


Folklore has it that ambient color has the power to relax or arouse the observer and enhance performance when executing cognitive tasks. We picked a number of commercially available colors that allegedly have the power to alter cognitive performance and the emotional state, and exposed subjects to them while solving a battery of cognitive tasks. The colors were “Cool Down Pink”, which is said to produce relaxing effects and reduce effort, “Energy Red”, allegedly enhancing performance via increased arousal, “Relaxing Blue”, which is said to enhance attention and concentration, as well as white as a control. In a between-subjects design, a total of 170 high school students carried out five tasks (number series completion, mental rotation, and memory for word categories, word pairs, and geometrical figures) while exposed to one of the four colors. The emotional state of the subjects was measured before the beginning and at the end of the experiment. The ambient colors did not have the predicted effects, neither on cognitive performance nor on the emotional state of the participants.

Multi-wavelength excitation method for measuring FWA-treated paper


Colorimetric properties of fluorescent materials depend on the SPD of the illumination. That is why most standards for evaluating them specify the illuminations, which are often hard-to-realize daylight illuminants. The presented method using commercially available LEDs enables accurate enough colorimetric measurements of FWA-treated papers or prints on them illuminated by the specified illuminant. The total spectral radiance factor of a fluorescent specimen, from which most colorimetric values are derived, consists of the luminescent spectral radiance factor and the spectral reflectance factor. This method separately estimates those of FWA-treated paper to add up to the total spectral radiance factor. The luminescent spectral radiance factor is obtained by estimating the SPD of luminescence excited by the specified illuminant as the weighted sum of the multiple SPDs of luminescence excited by the respective narrow band LED emissions at different wavelengths. The LEDs and their weights are determined optimally for generally used papers. The spectral reflectance factor is derived from the estimated SPD of the radiation with fluorescence excluded from the paper illuminated by visible illumination. The method was applied with five different illumination systems each using two or three narrow band LEDs in the excitation range. They were evaluated by measuring the total spectral radiance factors by D50 of seven FWA-treated papers and CMYK prints on four papers. The derived colorimetric values were compared to the respective references by the ideal D50.

Correspondence analysis of color–emotion associations


Emotions are often associated with colors, but what mediates color–emotion associations is not fully understood. This study examined associations between colors and emotions using correspondence analysis. The hypothesis that emotions are associated with colors through the correspondence between the hue circle and the circumplex model of emotion/affect was tested. Participants viewed 40 colors and reported a word that expressed an emotion that they associated with or felt in response to each color. Participants' responses were aggregated into a contingency table of colors and emotion words, and a correspondence analysis was conducted. An eight-dimensional biplot was obtained. The first and second dimensions were related to hue, and the hue configuration was similar to colors' spectral trajectory in the CIE xy space or the CIELAB a*b* color space. The configuration of emotions was not consistent with the circumplex model of emotion, which rejected the above hypothesis. The associations in dimensions 1 and 2 appeared to be mediated by the perceived temperature of colors and emotions. In dimensions 3–6, dimensions that seemed to reflect secondary associations based on cultural convention or personal experiences (such as white with emotionless and purity and blue with depression) were obtained. These results also demonstrated the usefulness of correspondence analysis for analyzing color–emotion associations due to its ability to reveal the underlying statistical structure of associations.

Digitally reconstructing van Gogh's Field with Irises near Arles part 2: Pigment concentration maps


Colors in many paintings of great art historical value have changed over time, due to the combined effects of natural ageing, accumulated surface grime, and materials added during later conservation treatments. The physical restoration of the colors in such paintings is not possible. This article describes one part of work done to digitally restore the colors of van Gogh's painting Field with Irises near Arles, dating from May 1888. We have used multispectral reflectance data to estimate absorption K and backscattering S parameters of Kubelka-Munk 2-constant theory. This was done for all 13 pigments known to have been used by van Gogh in this painting, and based on this the concentration maps for each of these pigments were calculated. We validated the calculated concentration maps in several ways. For some pigments, we were able to predict spots on the painting where the pigment is expected to occur in unmixed form based on visual examination. For several other pigments, the concentration maps could be shown to agree with XRF data. Finally, for some other pigments the concentration maps were supported by additional evidence from microscopic examinations, remarks in van Gogh's letters and from early color reproductions. For the 1.7 million pixels for which multispectral data is available, the average color difference between the calculated and measured spectral reflectance curves is CIEDE2000 = 1.05. This further confirms that the Kubelka-Munk calculations are well suited to describe the variety of spectral reflectance on the painting.

Digitally reconstructing Van Gogh's Field with Irises near Arles. Part 1: Varnish


Varnish layers applied to paintings often discolor as they age, upsetting the original colour relationships intended by the artist. The removal of aged varnish layers using physical and chemical means is a highly skilled and often time-consuming operation, which is not lightly undertaken. There are many aspects under consideration before embarking upon such treatment, including the visual result inferred by spot cleaning tests. In this article, we develop a technique for digital removal of discolored varnish that can help to envisage how a painting will look following cleaning treatment. The digital technique was applied to Vincent van Gogh's painting Field with Irises near Arles (May 1888), in parallel to the painting actually being cleaned, which allowed direct validation of the method developed. In the new method, we utilized not only hyperspectral data from parts of the painting with and without the varnish, but also experts' identification of spots on the painting where unmixed white pigment has been applied. The physical model that we use is based on Kubelka-Munk two-constant theory, commonly used to model the optical properties of paint. We show that with this model it is possible to determine the transmittance and reflectance of the varnish layer as function of wavelength. Results from previous studies confirm the calculated values. With the new method, we created a high-resolution digital image of the painting, as it would look after varnish removal, at a moment when the actual varnish was still present on the painting. The new method may help conservators and others involved in decisions made regarding issues of varnish removal from paintings, or may help to visualize the colors of a painting without discolored varnish in cases where its physical removal cannot be safely accomplished and so is not an option.

Red color in flags: a signal for competition*


The color-in-context theory and ecological valence theory suggest that color preference depends on the context and ecological object that define the psychological meanings of colors. The present study was conducted to identify the preference for the color red in national flags across the world. We explored 192 national flags across the world and found that red was the most frequently used color. Through a systemic examination of symbolic meanings behind use of the color red in flags, it was also found that the color red was often attached with an aggressive connotation. In contrast, the flags of the selected international collaborative organizations did not appear to prefer red. These results support the hypothesis of “red flag preference” in real-world competitive contexts. Limitations and future research directions are also discussed.

Colour meaning and consumer expectations


Deciding a colour for a product is a significant task for designers to attract consumer attention and communicate brand messages. It requires an initial analysis that explores consumer expectations within the sector, and this information is then used to inform development of a product design. This article discusses the application of the product colour development process during the initial phase of product design. Using a case study approach, one particular product category—a dishwashing liquid product was selected based on the suggestion from a leading U.K. consumer goods manufacturing company that colour is a major design factor for this product category. In the first phase of the study, interviews and an online survey were carried out with consumers (to explore what elements are important when they purchase a washing-up liquid product). In the second phase of the study, a colour meaning experiment was conducted to explore possible colours for dishwashing liquid packaging using a semantic differential method. The results show that yellowish and bluish green colours evoke positive responses while saturated and dark green colours are perceived more negatively.

Three-dimensional color prediction modeling of single- and double-layered woven fabrics


In this research, the three-dimensional structural and colorimetric modeling of three-dimensional woven fabrics was conducted for accurate color predictions. One-hundred forty single- and double-layered woven samples in a wide range of colors were produced. With the consideration of their three-dimensional structural parameters, three-dimensional color prediction models, K/S-, R-, and L*a*b*-based models, were developed through the optimization of previous two-dimensional models which have been reported to be the three most accurate models for single-layered woven structures. The accuracy of the new three-dimensional models was evaluated by calculating the color differences ΔL*, ΔC*, Δh°, and ΔECMC(2:1) between the measured and the predicted colors of the samples, and then the error values were compared to those of the two-dimensional models. As a result, there has been an overall improvement in color predictions of all models with a decrease in ΔECMC(2:1) from 10.30 to 5.25 units on average after the three-dimensional modeling.

Similarities and differences between male and female novice designers on color-concept associations for warnings, action required, and signs and equipment status messages


This research examined the male and female novice designers toward color associations for the concepts used for ‘warnings’, ‘action required’, and ‘signs and equipment status’ through a questionnaire-based study. A total of 178 Hong Kong Chinese final year undergraduate design students (89 males and 89 females) participated in the study. The test used required the participants to indicate their choice of one of nine colors to associations with each of 38 concepts in a color-concept table, so that any one color could be associated with any one of the concepts. For both male and female groups of novice designers, chi-square tests revealed a strong color association for each concept tested in this study (P < .05). The results showed males and females agreed on some color-concept association stereotypes which were therefore gender neutral. The male and female novice designers had the same color associations and similar levels of stereotype strengths for 21 concepts. The nine strongest and therefore most useful color-concept association stereotypes for both male and female novice designers were: red-danger, red-fire, red-hot, red-stop, red-emergency, red-error, blue-cold, blue-male, and green-exit. However, the male and female novice designers had different color association stereotypes for the standby (green vs. yellow), emergency exit (green vs. red), and toxic (purple vs. black) concepts, and the strengths of the 14 remaining associations for both groups were not at equivalent levels. Overall, it is anticipated that the findings of this study will act as a useful reference for novice designers and other design practitioners to optimize color coding in the design of ‘warnings’, ‘action required’, and ‘signs and equipment status’ messages.

An intelligent skin-color capture method based on fuzzy C-means with applications


Consumer behavior is complicated. In the cosmetic market, personal intuition and fashion trends for color selection are guidelines for consumers. A systematic method for female facial skin-color classification and an application in the makeup market are proposed in this study. In this article, face recognition with a large number of images is first discussed. Then, an innovative method to capture color at selected points is presented and complexion-aggregated analysis is performed. This innovative method is an extension of face-recognition theory. Images in RGB format are converted to CIELAB format during data collection and then Fuzzy C-means theory is used to cluster and group the data. The results are classified and grouped in Lab value and RGB index. Two programs are created. The first program, “FaceRGB,” captures color automatically from images. The second program, “ColorFCM,” clusters and groups the skin-color information. The results can be used to assist an expert system in the selection of customized colors during makeup and new-product development.

The “C test” for tritan discrimination


Background The aim of this study was to develop and evaluate a clinical standard capable of generating ordinal measures of monocular tritan discrimination. Design A novel pseudoisochromatic plate test was developed, called the “C test.” It contains 10 progressively desaturated plates arranged in perceptually distinct steps that provide a standard for analyzing the threshold for tritan discrimination. The most difficult plate that can be detected is the “C score.” Relevant diagnostic findings including the C score, Logmar acuity, Pelli-Robson score, and LOCS III lens grading were prospectively recorded in 568 eyes. Methods A total of 355 normal eyes were selected for statistical analysis. Main outcome measures The correlations between C score, Logmar acuity, and Pelli-Robson score with LOCS III grading were analyzed with Spearman rank analysis. Results The strongest correlations were between the Logmar acuity with posterior subcapsular cataract (PSC) (0.68), the C score with nuclear colour (NC) (–0.58), and the Logmar acuity with NC (0.57). The lower normal limit for the C score was 9 in pseudophakes and phakic eyes with NC < 3, 7 for eyes with NC = 3, but undetermined for eyes with NC > 3. A comparison of C score distribution between three distinct age ranges of pseudophakic eyes (n = 136) showed no significant variation (P = .486). The Spearman rank correlation between C score and Logmar acuity was 0.028, and between C score and Pelli-Robson score was 0.012. Conclusion The normal limit for the C score used under 800 Lux is 9 when NC < 3 and 7 when NC = 3 in all age groups.

Spectrophotometric measurement of human skin colour


This article focuses on human skin colour. Three different colour measuring instruments were used: a tele-spectroradiometer, a de:8° and a 45°:0° spectrophotometers. They were used to measure 47 subjects who were divided into four skin groups: Chinese, Caucasian, South-Asian, and Dark. Eight locations for each subject were measured. The spectral reflectance results were first compared. They all showed the “W” shape between the 550 nm and 580 nm as found by the other studies. Those from the tele-spectroradiometer had an increase from 600 nm while the others were flatter. The colorimetric data calculated from the spectral measurements revealed similar patterns to describe the colour distribution of each skin group. It was found that two scales: whiteness-depth, and blackness-vividness could well describe these distributions. The results also showed systematic differences between the four ethnic groups, between eight body locations, between two genders, and between the measurements from the three instruments.

Camera characterization for improving color archaeological documentation


Determining the correct color is essential for proper cultural heritage documentation and cataloging. However, the methodology used in most cases limits the results since it is based either on perceptual procedures or on the application of color profiles in digital processing software. The objective of this study is to establish a rigorous procedure, from the colorimetric point of view, for the characterization of cameras, following different polynomial models. Once the camera is characterized, users obtain output images in the sRGB space that is independent of the sensor of the camera. In this article we report on pyColorimetry software that was developed and tested taking into account the recommendations of the Commission Internationale de l'Éclairage (CIE). This software allows users to control the entire digital image processing and the colorimetric data workflow, including the rigorous processing of raw data. We applied the methodology on a picture targeting Levantine rock art motifs in Remigia Cave (Spain) that is considered part of a UNESCO World Heritage Site. Three polynomial models were tested for the transformation between color spaces. The outcomes obtained were satisfactory and promising, especially with RAW files. The best results were obtained with a second-order polynomial model, achieving residuals below three CIELAB units. We highlight several factors that must be taken into account, such as the geometry of the shot and the light conditions, which are determining factors for the correct characterization of a digital camera.

Predicting personality associations evoked by multicolored appearance of virtual agents: an exploratory study


Designing agents' color appearance that can evoke desired color-personality associations (CPAs) is still a challenge. To respond to the challenge, this study proposed a multicolor personality index (MCPI) model to predict the CPAs evoked by agents using the color-personality indices for single colors together with the histogram of agents' image. Specifically, the color personality index for each bin of an agent's histogram was first calculated based on the color-personality indices for single colors; then, the predicted values of CPAs were obtained by calculating the weighted average of color-personality indices of all bins in the histogram. To improve the MCPI model, a simple color-attention index model was proposed to evaluate the effects of color on attention and the effects were introduced into the MCPI model, that is, the multi-color personality index based on color attention (MCPI-CA) model. To validate the two models, an experiment was conducted to collect the CPAs of five traits (i.e., extraverted-introverted, moody-unemotional, agreeable-disagreeable, organized-disorganized, and wide interests-narrow interests) evoked by the multi-colored appearance of agents. The results showed that (a) observers in general perceived the CPAs evoked by color appearance in similar way; (b) for most agents, the CPAs evoked by multi-colored appearance could be predicted well by the MCPI model; and (c) the MCPI-CA model usually had better performance than the MCPI model due to the inclusion of the effects of color attributes on attention. In addition, the limitations of the proposed models and their implications for designers were also discussed.

Long-term changes in Japanese women's facial skin color


It has been suggested that skin color changes not only with advancing age but also with the times. The purpose of this study was to investigate changes in Japanese women's facial skin color over 25 years, as well as the changes in skin pigmentation that affect skin color. First, skin color changes in terms of Munsell color values were investigated. A total of 3181 Japanese women residing in the greater Tokyo area were enrolled, and datasets were collected using spectrophotometers, designated as the 1991, 2001, 2005, and 2015 data. The mean Munsell hue, value, and chroma were calculated for each measurement year. Next, the concentrations of melanin and hemoglobin were calculated from spectral data, to investigate changes in skin pigmentations. Finally, Monte Carlo simulations were performed to verify that the suggested changes in skin pigmentations brought about skin color changes. As a result, skin color significantly changed toward high lightness, low saturation, and high yellowness from the 1991 data to the 2001 data. From the 2005 to 2015 data, the skin color distribution shifted toward lower saturation and increased redness. In addition, the concentration of hemoglobin decreased significantly from the 1991 data to the 2001 data, while the melanin concentration decreased significantly from the 2005 data to the 2015 data.

Improving color reproduction accuracy of an OLED-based mobile display


For improving color reproduction accuracy of mobile displays, we recently developed a generic model for device-specific display characterization model that also accounts for the influence of illuminance from ambient light. In the present article, this MDCIM model (Mobile Display Characterization and Illumination Model) is applied to a Samsung Galaxy S4 display, representing OLED displays. The performance of the model was tested by determining the values of all model parameters using publicly available technical data only. We organized visual tests under various ambient illuminance levels from 600 to 3000 lux. Seven observers compared the color of displayed images with the color of physical samples. With the MDCIM method, the quality of the color match was shown to improve considerably as compared to using only device-independent encoding color space. On a five-point scale to quantify color reproduction accuracy, the MDCIM resulted in more than 1 unit improvement at 1000 lux illuminance. At lower and higher illuminance, the improvement was even larger. Color reproduction accuracy was found to be at least reasonable, according to the subjective assessment of visual observers, for more than 75% of the samples when using the MDCIM method, but only 20% or less when using the common device-independent encoding color space.

Impact of spectral power distribution of daylight simulators on whiteness specification for surface colors


The impact of spectral power distribution of daylight simulators (ie, D65 simulators) on surface whiteness specification was investigated by focusing on how CIE whiteness and tint values of 8 whiteness samples with fluorescent whitening agents (FWAs) vary under different D65 simulators. Large variations in both whiteness (∼16 points) and tint (∼1.6 points) are observed under the D65 simulators above BB grade, as characterized using the CIE metamerism index. However, it is found the variations of the whiteness and tint values are smaller under the D65 simulators whose radiant power in the UVA band (ie, 300-340 nm) was within ±30% in comparison to CIE standard D65 illuminant, as defined in BS 950, which may be a better alternative for evaluating the quality of a D65 simulator for surface white specification using CIE whiteness and tint formulas. The findings also suggest the necessity to fine-tune or revise the CIE whiteness and tint formulas to characterize the surface whiteness under nonperfect D65 simulators or arbitrary light sources.

Comprehensive color solutions: CAM16, CAT16, and CAM16-UCS


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

Do red prices also work online?: An extension of Puccinelli et al. (2013)


In a recent article, Puccinelli et al. examine the effect of the color in which prices appear in print flyers on consumers' perceived savings. Puccinelli et al. find that the effect is moderated by gender: unlike female consumers, men think they are being offered a better deal when prices are presented in red than when they are presented in black. The advertisements with prices in red also put men in a more positive state. This note replicates Puccinelli et al.'s main experiment in a different context (online vs. print) and in a different cultural setting (Belgium vs. the USA). In line with Puccinelli et al., we find that men perceive the online store with red prices as offering better value. But, intriguingly, it does not appear to make men feel more positively. One possible explanation is that red prices work differently online.

Pigments & dyes in a collection of medieval illuminations (14th–16th century)


The Marcadé Collection (Bordeaux Cathedral treasury) consists among other objects of 42 illuminations (14th to the 16th century) from five origins (France, Italy, Germany, the Netherlands, and Spain). For better knowledge of these miniatures, the pigments and dyes have been analyzed in ten illuminations chosen in order to represent the diversity of the collection. The aim of this study is to establish a panorama of the pigments and techniques used in medieval miniatures through the study of a set of manuscripts and to discuss the potentialities of the analytical techniques in order to reach this objective. Hyperspectral imaging is a rapid, mobile and noninvasive technique. It gives reflectance spectra for each pixel of the image. The datacube obtained was treated in order to visualize images and reflectance spectra. The software allows the mapping of the pigments by comparing spectra with those of our database. As some interpretation difficulties can appear for dyes or mixtures, to confirm the identification, point techniques such as Raman, X-ray spectroscopy, and Fiber Optic Reflectance Spectroscopy in the Near Infrared range were used. Analyses allowed access to the palette for each illumination and showed the colours diversity and pigments treatment. They increase knowledge about the materials used and the evolution of them during the time period: the use of dyes and shell gold became more important at the end of the period. The analytical choice respects the fragility and preciousness of these artworks and helps the fast data acquisition for the materials identification.

A statistical analysis for correlation approach to compensate the measured CIELAB colorimetric data for temperature alterations


The main focus of this work was to elucidate the further question of whether the color change correlated linearly with the surface temperature alteration or not. We selected and grouped the colored samples, which were in the form of textile, ceramic, plastic, paint, and ink. Those samples were first measured by IR Thermometer to record exact surface temperature, followed by an immediate color measurement using a spectrophotometer. The color variations of these samples were recorded from about 20°C to 60°C. The trend of CIELAB color coordinates was plotted against surface temperature. The dependency between each CIE colorimetric coordinate and the object's surface temperature was statistically evaluated using Pearson's r, R value, and R-square analysis. A very strong correlation was observed for ceramic, paint, and ink samples tested, while the textile and plastic sample also exhibited a strong trend. The results added new information about the potential correlation between colorimetric data and temperature. Implications for the future research are discussed.

Multivariate Gaussian subspatial regression applied to predict the effect of phosphate crystallization aging on the color in silicious conglomerates


A new methodology has been applied to the experimental data obtained about a white siliceous conglomerate from Zamora (Spain), which was subjected to 25 cycles of 2 types of aging [freezing/thawing with cooling/heating (T1) and freezing/thawing with cooling/heating + phosphate crystallization (T2)]. Our model (multivariate Gaussian subspatial regression) allows the behavior and prediction of the chromatic coordinates (L*,a*,b*), including more than 25 cycles, to be analyzed. This model is much more flexible than classical models as it allows multiple variable combinations to be predicted in a dynamic way. The final result showed that the conglomerate experiences darkening, yellowing, and reddening, as the number of cycles increase and that the darkening is much less pronounced in T2 due to phosphate crystallization.

Image color adjustment for harmony with a target color


Although a number of methods have been developed for image adjustment in various applications, very little work has been done in the context of visual design. In this regard, this article introduces a novel and practical context of image color adjustment and develops a method to adjust an image for harmony with a target color. The experiment with designers revealed that designers made significant changes in hue dimension, and preferred to promote color similarity between the image and the target color. Based on insights from designers, we proposed a method to achieve a harmonious combination of an image and a color element by increasing the hue similarity between them. The result of a user test revealed that our method is particularly useful for images with nonliving objects but less effective for images involving human skin, foods, and so on. It is expected that the practical context investigated in this study can promote a variety of related studies that satisfy the tangible needs of industries and academia.

Performance of the Ishihara, D-15, and City University colour vision test as a function of intraocular straylight


Three colour vision tests, the Ishihara test, the City University Test (CUT), and the D-15 test were studied as a function of induced intraocular straylight, using a commercially available light-scattering filter. Thirty young individuals (aged 17-28 years) with no ocular abnormalities and normal colour vision participated in the study. Intraocular straylight was estimated in all individuals using a psychophysical compensation method with the C-Quant straylight meter, with and without the light-scattering filter which caused an increase in intraocular straylight typical of that found for cataract. Under normal viewing conditions all the subjects passed each of the 3 tests with no errors. When viewing the Ishihara test plates through the filter, 10 out of the 30 observers made at least 1 error. Three subjects also made errors on the desaturated CUT test plates, but all subjects still passed the D-15 test with the filter. The errors in the Ishihara test correlated with the amount of intraocular straylight, as measured with the C-Quant. This study indicates that interpretation of the Ishihara test in a clinical environment will be made more difficult in individuals with higher levels of straylight.

Multiple roles of color information in the perception of icon-type images


Despite the ubiquity of icons in computing and mobile devices, the role of color in icon-based interface design has yet to be fully elucidated. This study began by conducting a card sorting experiment to determine the importance of color in the perception of commercial icons, as opposed to the simpler icons typically used in a laboratory setting. The study also sought to ascertain the importance of color when considered alongside other visual attributes in the general perception of icons. Participants were then asked to answer preset questions as a means of determining the relationship between the known color properties (e.g., hue, saturation, and brightness) of icons and their functional meaning, effectiveness in conveying meaning, and visual attractiveness. Finally, the speed and accuracy was assessed by which participants recognized well-known icons rendered using familiar and unfamiliar colors. The empirical results identified color as an important attribute in the process of sorting icons, far exceeding other visual attributes including shape, complexity, pictorial style, and orientation. Nonetheless, it appears that color is not necessarily dominant in the initial stages of sorting. The results also revealed that color is closely related to visual attractiveness but largely irrelevant to effectiveness in the conveyance of meaning. The study also confirmed that correct color information is crucial to naming accuracy and the speed at which icons are recognized. Finally, the results indicate that icons lacking a unique symbol as a cue to recognition rely heavily on their signature color for identification. This study opens up several avenues of research by which to enhance our understanding of the functional role of color in icon perception.

Color characteristic of Castle District built on the hill


In this article the used of the colordynamic planning method is described and applied as an example to the façade of a building in Buda. The method of colordynamic planning consists of 3 essential parts. In the first part we decide on the limits of the color range to be used, based upon the requirements of the subject of planning. The decision on these limits is closely linked to the coordinates of the Coloroid system. In the second part the planner creates harmonic color scales from the previously selected color range. In this work he is helped by rules of the Coloroid system, based on harmony thresholds. In the third part the planner selects the color harmony combinations considered suitable by him. Following that, he finalizes the Coloroid coordinates of the proposed colors most suitable for the project. For the presentation of the colordynamic planning method, based on the Coloroid system, we use a real database of a colordynamic plan, which was awarded the first prize in an international competition.

Influence of vehicle on historical pigments colour


The colour of a paint layer is determined by the pigments mixed with a vehicle and painted on a support. According to their chemical nature, the vehicles are substances that, after drying or hardening, produce an uniform and homogeneous layer. With the aim of quantifying the influence of the medium on the specification of the painting colour, we realized samples of paintings. We considered pigments and dyes of the artist's hues using the vehicles typical of ancient times: oils (especially linseed and poppy oils), casein and egg yolk, mixed according to old recipes. Measurements were performed by reflectance spectrophotometry observing the Spectral Reflectance Factor (%SRF) trend and calculating colour changes. The colorimetric study was carried out in the CIELAB colour space related to the CIE 1964 standard observer and with the D65 illuminant. The results were evaluated also on the basis of the distribution of pigment particles on paint layers observed by scanning electron microscopy.

Physical indices for judging appearance harmony of materials


In visual design, harmony refers to the similarity among objects and the components of these objects that appear as if they belong together. Harmony is related to the body, mind, and emotions as we relate to our living space, which means that the harmony of real objects is an important characteristic. Although the appearance harmony in specific materials has been investigated, harmony among different materials has not received adequate attention. In a previous study, we investigated the appearance harmony among various materials by psychophysical experiments. In this study, we correlated the psychophysical evaluations obtained from the experiments and the physical properties of the materials. By analyzing the relationship between psychophysical evaluations and the physical measurements for each material pairs based on cluster analysis, we found that the property of texture represented by the anisotropy histogram and that of reflectance obtained from the data of the bidirectional reflectance distribution function are important indices that can be used to judge the harmony of materials. In particular, the texture properties were more effective in judging the appearance harmony of material pairs in the fixed condition for illumination and viewing angles, and the reflectance properties were superior for the material pairs in the variable condition for illumination and viewing angles.

Progression of color decision making in introductory design education


Color comprises both subjective and objective aspects within its contextual nature. Research on color design tends to explore this seemingly contradictory concerns from theoretical point of view, as well as architectural and design practice. The aim of this study was to observe subjective, intuitive or heuristic and objective, knowledge-based or analytical attitudes toward color in design education. In the study 84 introductory design students were surveyed progressively to understand their color decision criteria after completion of three 2-dimensional colored exercises, specific in terms of color education. Students' responses to open-ended questions were coded according to the 5 categories, under 2 decision making processes derived from the literature; heuristic approach: preferential and symbolic criteria, and analytic reasoning: formal, thematic, and systematic criteria. A distinction between associative and emotional aspects of symbolic criteria was also revealed by the data analysis. The findings showed a shift from heuristic responses to analytic reasoning, as expected. Additionally, it is also investigated that students not only used heuristic approaches but also analytical components (formal and systematic) of color decision making in varying degrees as well, even before any color subjects covered. Thematic color decisions became a major part of the students' design considerations upon completion of color subjects. The observed increase in the number of color criteria interrelated by the students' among almost all categories explicated a complex decision making process particularly in color design and education. These findings were expected to lead to some further understanding in color decision making in design.

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Performance of advanced color difference and CAM02-based formulas in prediction of the Crispening effect for reflective samples


The Crispening effect is defined as an increase in the perceived color difference of the two stimuli, when their color (chromaticity or luminance) is close to the background on which the two stimuli are compared. In this study, the amount of the Crispening effect for three achromatic backgrounds and also the performance of six different color difference formulas (CDFs) for prediction of this effect have been investigated, by preparing 85 sample pairs in 9 CIE's recommended color centers. Regarding the results, the maximum (50%) and the minimum (4%) amount of the Crispening effect belong to the gray and the purple centers, respectively. According to the results of a comparative test, the Crispening intensifies when two stimuli have just lightness difference instead of just chromaticity difference. The highest variation was for the gray samples, in which the amount of the Crispening effect increased from 35% to 65%. By using PF/3 and STRESS index, it is also concluded that CMC and CIEDE2000 perform better than CAM02-SCD and CAM02-UCS in prediction of the Crispening effect on the dark gray and gray backgrounds. According to the results, the significant differences between the performances of the CDFs disappear when the luminance of the background increases. Huang's power functions also do not improve these results significantly. Furthermore, the results indicate that the traditional L* equation used in CIELAB performs similar to the Whittle's formula in prediction of the Crispening effect for reflective samples, and no significant difference was obtained.

New colour appearance scales for describing saturation, vividness, blackness, and whiteness


This article describes the development of new models for predicting four colour appearance attributes: saturation, vividness, blackness, and whiteness. The new models were developed on the basis of experimental data accumulated in the authors' previous study, in which the four colour appearance attributes were scaled by 64 Korean and 68 British observers using the categorical judgment method. Two types of models were developed: the ellipsoid-based and the hue-based. For the former, the perceived saturation, vividness, blackness, and whiteness were modeled in the form of colour-difference formulae between the test colour and a reference colour. For the latter, blackness, whiteness, and chromaticness scales were modeled by estimating hue-dependent lightness and chroma values for the “full colour” in the framework of Adams' equation. The new models were tested using NCS data and were found to outperform some of the existing colour appearance models.

Evaluation of uncertainties for CIELAB color coordinates


CIELAB color coordinates are characteristics of visible object's spectra widely used in color science, and a reliable evaluation of the uncertainty associated with measured color coordinates is desirable. The calculation of CIELAB color coordinates requires the application of a nonlinear transformation. We consider two ways to calculate the uncertainty of CIELAB color coordinates that originates from the uncertainty of the observed spectrum. The first approach is based on a linearization of the nonlinear transformation and a propagation of variances and covariances. The second approach is a Monte Carlo procedure that completely accounts for the nonlinearity of the transformation. While the approach based on linearization results in analytical formulas, the adequacy of linearization ought to be checked and the proposed Monte Carlo method can serve as a reference method for this purpose. We illustrate such proceeding in a large range of scenarios and explore those cases for which the method based on linearization may safely be applied.

Chromatic adaptation to illumination investigated with adapting and adapted color


The state of chromatic adaptation was investigated by using the two-room technique. This technique involves a subject in a room who looks a white board in a separate test room through a window and judges the color of the window using the elementary color naming method. When the subject room is illuminated with a colored light and the test room with a white light, the window appears to be a very vivid color, for which the apparent hue depends on the color of the subject room. The color is referred to as the adapted color. The subject also evaluated the appearance of the illumination color of the subject room, which is called the adapting color. Two types of illuminating light in the subject room, fluorescent lamps with 7 colors and LED lamps with 19 colors, were employed. The adapting and the adapted colors were plotted on a polar diagram that was used in the opponent color theory, from which the hue angles were obtained. The hue angle difference between the two colors did not appear to be 180° except for one pair of adapting and the adapted colors, which implies that chromatic adaptation does not follow the opponent color concept. An improvement was achieved to explain the results by introducing complementary colors relation between the adapting and adapted color.

Color breakup visibility thresholds for 2-field sequential colors


Nowadays local primary desaturation has been proved to be an effective method to suppress the color breakup for field-sequential-color (FSC) displays. However, little attention has been focused on the interaction between various subfield colors and the color breakup visibility. In this article, a perception experiment was conducted with the help of a 120 Hz 2-field FSC display to investigate the thresholds of color breakup visibility along different hue directions with a constant white point in the standard color space. The experimental results show that the color breakup visibility is various when using different subfield colors for temporal combination. A relative high threshold value or low sensitivity of color breakup visibility can be observed when subfield colors are chosen along the blue-yellow direction while becoming perceptible easily along magenta-cyan direction. The results and analysis of our experiments are promising to optimize the performance of local primary desaturation. Meanwhile, other applications using the temporal color fusion such as tunable lighting can also benefit from the conclusion of our work to suppress the color breakup effect.

The effect of unit k/s calculation and spectral overlapping on the performance of color matching


There are several approaches to dyeing recipe formulation in the textile industry, because the accuracy of computer recipe prediction is not very high. There are several theories such as colorimetric and spectrophotometeric appraches on color reception. This work addressed the effect of the calibration method as the calculation of unit k/s and spectral overlapping of the components of the mixture on the accuracy of recipe prediction in dyeing nylon with acid dye. To this aim, the unit k/s was calculated using single and binary mixture samples. Two types unit k/s were used for the recipe prediction of ternary mixture dyed samples with low and high overlapping reflectance spectra. The obtained results indicated that the unit k/s of single component differed from the unit k/s of bicomponent mixture. The accuracy of recipe prediction using unit k/s of single component was less than that of the binary mixture. However, the performance of the recipe prediction of high level overlapping was found to be more than that of the low level overlapping mixture. Subsequently, the accuracy of color matching depended on the reflectance spectra similarity (spectral overlapping) of the components of the mixture.

Using principal component analysis technique in the instrumental shade sorting of textile fabrics


In the present study, the CCC shade sorting method was employed with CMC(2:1) color difference formula on the colorimetric data (CIEL*a* b*) of 37 fabric color sets. The k-means non-hierarchical clustering technique was also combined with the CCC shade sorting method to increase its efficiency. The results of this combined method showed a slightly better performance, as compared with the CCC method. Also, a new proposed shade sorting method by the application of principal components analysis (PCA) technique was used to identify and remove the outliers in each of the color sets. The results of separating the outliers showed that although the diameter of group criterion was improved significantly, the number of groups, the number of singleton groups, and the number of groups with low samples were increased considerably. Finally, in a second new proposed shade sorting method, PCA was used as a data reduction tool on the colorimetric data of the 37 color sets. Then, the two first principal components in combination with a k-means clustering technique were used for the clustering of the samples in each color set. The results of this second new proposed method were found to be similar to the CCC method considering number of group and fabric consumption criteria. The second new proposed method revealed a moderately worse result, with regard to the diameter of group criterion, than the CCC method.

Research on the detection of fabric color difference based on T-S fuzzy neural network


T-S fuzzy neural network algorithm is used to establish the mapping relationship from the RGB space to the L*a*b* space, which avoids the complex process of color space conversion. Meanwhile, the block method is adopted to detect color difference of dyed fabric that is wide format and wide viewing angle. Color differences in different regions can be calculated with Color Measurement Committee color difference formula based on T-S fuzzy neural network. Experimental results are in accordance with the spectrophotometer measurement, which proves that T-S fuzzy neural network algorithm used in real-time color detection process is effective and feasible. Workers can make corresponding adjustment on-line according to the deviation to ensure the quality of fabric color and reduce the loss.

Perceptual and emotional effects of light and color in a simulated retail space


This article aims to address two aspects of lighting often treated intuitively by designers in charge of creating retail atmospheres, that is, the impact of color and light distribution, as design variables. The study comprised a controlled experiment with a repeated measure design with three directions of lighting (front, overhead, and wallwasher), as the within-subject factor and four color combinations of the walls (yellow-blue, magenta, gray, and green-magenta), as the between-group variable. The perceptual (visually) and emotional responses of 184 participants revealed the interplay between light and color on these psychological outcomes. Specifically, the results showed that the overhead direction of lighting improves the appearance of the less favored color conditions, either in terms of lack of visual complexity (monochromatic) or color itself (gray). In turn, the wallwasher lighting emphasized these attributes, differing according to visual or emotional aspects. In retailing, emotional dimensions such as activation and evaluation are desired, and they were confirmed across all the lighting and color conditions of this study. The results provide designers with certain perceptual cues regarding colors and their lighting mode to create desirable impressions and affect in retail spaces.

Color-emotion associations, designing color schemes for urban environment-architectural settings


Color in urban design has become an important issue, each city may present different colors which help to define and describe its architectural features. In the study, color in urban design with architectural setting is studied, façade colors are analyzed with a specific emphasis on the following research questions; “Can color schemes be designed in respect to color-emotion associations?” and “Are color-emotion associations affective while designing architectural setting-urban environment?.” Non-color experts, 170 people, from different European and non-European countries were asked to match the most appropriate adjectives with the given street views in accordance to their color schemes. In the first step, the effect of color is identified in relation to architectural environment-urban setting, second the relative effect of color is studied as a component of the material. A categorical specification on color cognition and linguistic level of representation is attempted. The results can be a starting point to highlight the importance of preparing color schemes in regard to color-emotion associations. Abstract color schemes may also provide us an idea about image setting, especially at design process stage. In the study, keywords are linked as environment-response pairs; such as quiet, calming, lively, exclusive, reserved, and natural. Human psychophysical structure such as “warm-cool,” “heavy-light” in regard to visualizing certain colors are evaluated and described in terms of building materials.

Color loci placemaking: The urban color between needs of continuity and renewal


The article presents the theoretical framework and the operational concepts of a research, finalized to explore and verify the prerequisites of an approach to urban color that, while recognizing to color the flexible as well as transient capacity to respond to the successive and multiple demands that characterize the urban space, sees a possible way of coexisting between the needs of continuity and renewal. Searching to understand the modalities and possibilities through which colour can intervene in the processes of transformation of the city to support both the needs of resignification and reappropriation and those of conservation and enhancement of the vital identity of each single place, the research looked on one side to the experiences gained within the colour plans and Lenclos' geography of colour and on the other side to the different and diversified experiences developed within the idea and practice of placemaking, aimed at the recognition and enhancement of the collective and plural creative dimension that colour seems effectively able to interpret. The term “color loci placemaking” was introduced to summarize this mode/possibility of understanding and approaching urban color, characterized especially by the attention for the specificity of each single place and the human factor underpinning place-experience.

A comparison between wishes and status: Gray is not the preference for residents while the city shows neutral colors


Urban color has become one of the hot topics in China since 2000. To provide suggestions for making the urban color plan for Changzhou of about 253 square kilometers in 2011, the research group evaluated the visual quality of the present architectural color in real urban space and investigated the residential attitude for the present and the future ones. Open-ended questionnaire of 1065 was taken effectively face to face accompanied with NCS Cascade 980 to understand the residents' attitude about the present architectural color in Changzhou city, and the expectations for the future. At the same time, an overall survey and evaluation on the present architectural color was conducted from the aspects of materials, functions, environmental and color relationship as well as the color code itself. Data reveal the residents' attitude to color preferences is more tolerant in hue with no special color bias, and inclined to those with obvious chroma and clear color predisposition, not very vivid, nor very dark. While the site survey shows the present color focuses mostly in high or middle-high brightness, neutral ones. In site evaluation and analysis, architecture obtained good scores are those have obviously color predisposition. Colors that are inclined to good scores still have obvious color tendency but is lighter than that of good ones and mostly concentrate in the middle high and high brightness. Although still shows warm colors the most, the color tendency was not so obvious and the proportion of grayish ones increased. As to colors inclined to bad, very large proportion of grayish color existed. Actually, the most insurance color people usually thought, if has no good façade form supporting, is difficult to obtain a pleasant visual effect. Also, if the material is not in agreement with the color, the visual effect will be even worse.

An aesthetic measurement method for matching colours in product design


Since it is important to know how to evaluate human emotions reflected in the image of a product during the process of product design precisely, a means of evaluating the aesthetic measurement of the image of a product with colour matching is proposed in this article. This method entails a solid visual angle of the subject, the distribution of colour-area ratios, and colour images as experimental samples for colour matching. The evaluation was conducted based on a formula of the aesthetic measurement of the coloured area. To ensure that the entire practical colour co-ordinate system was covered, 111 coloured chips were distributed throughout the implementation procedure. The aesthetic measure of colour harmony in this study was calculated based on aesthetic measure theory; moreover, each of the three given images received three symbolic colour combinations before using the fuzzy theory to determine the relationship between the image and the colour combinations of the products. Observers' evaluations of the fuzzy theory and the aesthetic measurement model were then compared, and the results showed that the proposed method succeeded in obtaining a high degree of satisfaction for the top 2 ranked samples in the aesthetic measurement model evaluation and human evaluation. Although only 2 product designs were used as examples for performing the evaluation procedure, the procedure can also be applied to other products.

Color specification of two new resin composites and influence of stratification on their chromatic perception


Accurate color reproduction in conservative dentistry is fundamental to the aesthetic success of the restorations. The need to specify the color objectively has been known for some years, and this article aims to make a contribution to this field. This work is part of a multidisciplinary research project, and it has a double aim. The first purpose was to measure the color differences between the two new composite resin restorative materials and the most used dental color scale. Measurements show some differences from color shades indicated by the manufacturers and those obtained from experimental data. The influence of different order of enamel and dentin layers on color perception was also investigated to evaluate clinical strategies useful to obtain desired result. Relevant differences are observed in the stratification of dentin and enamel discs especially for one of the two studied composites.