Assessing the affective feelings of two‐ and three‐dimensional objects

The aim of this study is to investigate the impact of physical appearance attributes (in terms of color and shape) on our affective feelings of 2D and 3D objects. Twelve colors were studied, each consisting of 12 two‐dimensional and 12 three‐dimensional shapes. This resulted in 144 2D and 144 3D color‐shape combinations. Each color‐shape combination was assessed using 20 emotion scales in a viewing cabinet by a panel of observers with normal color vision. The results show that there are five underlying factors of these 20 scales, i.e., “activity,” “weight,” “heat,” “softness,” and “complexity”. The first three factors were mainly related to color and the other two were linked with shape. © 2008 Wiley Periodicals, Inc. Col Res Appl, 34, 75–83, 2009.     

Color vision assessment‐1: Visual signals that affect the results of the Farnsworth D‐15 test

The Farnsworth D‐15 test (D‐15) is commonly used to screen for moderate to severe congenital color vision deficiency. The aim of this study was to establish reliable D‐15 statistics for normal, deutan and protan subjects, and to investigate the different visual signals one can use to carry out the test, even in dichromats and rod monochromats. Six hundred and seventy‐four subjects were examined using the D‐15, the Colour Assessment and Diagnosis test and the Nagel anomaloscope. A rod monochromat and five dichromats were tested using the standard D‐15 protocol before the caps were separated into two groups and subjects were asked to repeat the task. D‐15 spectral radiance data, measured under D65 illumination, were used to estimate differences in photoreceptor excitations for each of the caps. When no crossings and up to two adjacent transpositions on the D‐15 results diagram are accepted as a pass, 100% of normal trichromats, 54% of deutans and 43% of protans pass the D‐15. A rod monochromat and two protanopes and deuteranopes were able to complete the D‐15 when the caps were separated into two groups, despite severe loss or even complete absence of color vision. When up to two adjacent transpositions are accepted 50% of color deficient subjects, some with severe red/green loss, pass the D‐15. While the D‐15 is normally used to screen for moderate to severe color deficiency, subjects with severe loss can still use combined, residual red/green, yellow/blue and luminance signals to pass.     

Chromatic variation of Ishihara diagnostic plates

Ishihara diagnostic plates of the same design from 10 books (five editions, two books from each) were compared to determine the chromatic and diagnostic variability. The responses of 17 red–green (r‐g) deficient subjects were recorded and compared. Spectrophotometric analysis was also performed on five of these books. The chromaticity coordinates of the colored dots were plotted in the 1931 International Commission on Illumination (CIE) chromaticity diagram in reference to the protan and deutan confusion lines. The relative lightness of the figure compared to the background was calculated as the Weber contrast according to the Smith–Pokorny fundamentals for both protans and deutans. Significant diagnostic variation was found among the r‐g–deficient subjects. The chromaticity coordinates and the relative lightness of the colored dots were also found to have significant variations. We were able to account for many of the diagnostic differences based on the chromaticity and relative lightness variations among the books. Spectrophotometric analysis may provide additional quality control for these plates. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 267–276, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10161     

Detection and modification of confusing color combinations for red‐green dichromats to achieve a color universal design

Color‐vision deficiency is a relatively common genetic condition, which often leads to the obstruction of necessary information in colored images. It is important to minimize such inconvenient effects in communication using colored images from a universal design perspective. The universal design principle stipulates that all environments and products should be usable by all people, regardless of age, physical attributes, and ability. This article proposes a method to detect color combinations in a given image that would confuse color dichromats, and suggests a way in which to modify them to make the image easily distinguishable for both normal and dichromatic observers. Confusing color combinations were detected based on a color‐difference calculation using simulations of how the color would appear to dichromats. The confusing colors were then modified based on the minimization of an evaluation function, which was defined as the sum of the degree of confusion and the degree of color change from the original image. Several colored images obtained by the proposed method were compared with the originals by red–green dichromatic observers who judged them to be clearer, thereby confirming that the proposed method was effective for color rendering for universal design. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 203–211, 2008     

Color appearance and color connotation models for unrelated colors

The purpose of this research is to investigate the color appearance and color connotation of unrelated colors. To investigate color appearance (i.e., brightness, colorfulness, and hue) for unrelated colors, 22 observers have answered their color appearance for 50 unrelated color stimuli using the magnitude estimation method. Perceptual data obtained by the experiment is compared with the color attributes data estimated by unrelated‐color appearance models, CAM97u and CAM02u. It is found that both models perform reasonably well but the performance of CAM02u is better than that of CAM97u. For investigating color connotation for unrelated colors, 32 observers have judged their color connotation for the 50 unrelated color stimuli using the 10 color connotation scales (i.e., “Warm – Cool,” “Heavy – Light,” “Modern – Classical,” “Clean – Dirty,” “Active – Passive,” “Hard – Soft,” Tense – Relaxed,” “Fresh – Stale,” “Masculine – feminine,” and “like – Dislike”), and semantic differential method is used for measurement. It is found that the color connotation models developed for related colors perform poorly for unrelated colors. Experimental results indicate that brightness attribute is confusing to estimate and does not affect color connotation significantly for unrelated colors. Based on the psychophysical data, new models for “Warm‐Cool”, “Heavy‐Light”, “Active‐Passive” and “Hard‐Soft” were proposed using CAM02u hue, brightness, and colorfulness. Color connotations for unrelated colors are classified into three categories, which “Color solidity,” “Color heat,” and “Color purity.” © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 40–49, 2015     

Quantifying variations in personal color spaces: Are there sex differences in color vision?

We report a search for group differences in color experience between male and female subjects, focusing on the relative prominence of the axes of color space. Dissimilarity data were collected in the form of triadic (odd‐one‐out) judgments, made with the caps of the D‐15 color deficiency test, with lighting conditions controlled. Multidimensional scaling reduced these judgments to a small number of dimensional‐weight parameters, describing each subject's sensitivity to color axes, i.e., how much each axis contributes to the inter‐color dissimilarities perceived by each subject. Normal trichromatic subjects in two age bands were examined, teenagers and university students, and in both cases males placed significantly less weight on a ‘red‐green’ axis, and more on ‘lightness’. We consider the implications and possible explanations. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 128–134, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10232     

Light wavelengths of LEDs to improve the color discrimination in Ishihara test and Farnsworth Panel D‐15 test for deutans

This study was performed to determine significant light wavelengths to improve color discrimination ability of subjects with deutan. We conducted both the Ishihara test and the Farnsworth Panel D‐15 test for subjects with deutan and normal color vision. Seven different LED lights from 450 to 660 nm and an additional D65 white lamp were utilized to change the lighting conditions, including the wavelength and intensity. The results of the Ishihara test and D‐15 test showed that color identification of deutans was markedly improved with the longer wavelength LEDs regardless of the intensity of the additional D65 lamp. Notably, the error rates of deutans in the Ishihara test were <25% for LED wavelengths of 630 and 660 nm. In the case of subjects with normal color vision, the D65 lamp abolished the errors in the Ishihara test, regardless of the LED wavelength. Addition of the D65 lamp also decreased the number of crossings in the D‐15 test. These results suggested that illumination by LED light with longer wavelengths, such as 630 and 660 nm, may provide deutans with greater red‐green discrimination ability in both the Ishihara test and the Farnsworth Panel D‐15 test. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 424–430, 2017     

Semantic interpretation of color differences and color‐rendering indices

A series of visual experiments were carried out to rate the similarity of color appearance of two color stimuli on categorical and continuous semantic rating scales. Pairs of color stimuli included two copies of the same colored real or artificial object illuminated by a test light source and a reference light source. A formula was developed to predict a category of color similarity (e.g., “moderate” or “good”) from an instrumentally measured color difference. Given a numeric value of a color difference between the two members of a pair of colors, for example, 2.07, the formula is able to predict a category of color similarity, for example, “good.” Because color‐rendering indices are based on color differences, the formula could be applied to interpret the values of the new color‐rendering index (n‐CRI or CRI2012) in terms of such semantic categories. This semantic interpretation enables nonexpert users of light sources to understand the color‐rendering properties of light sources and the differences on the numeric scale of the color‐rendering index in terms of regular language. For example, a numeric value of 87 can be interpreted as “good.” © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 252–262, 2014; Published online 14 March 2013 in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/col.21798     

Investigating the personality associations evoked by single colors: An exploratory study

Despite the crucial role of color appearance in forming first impressions, it is still not clear how color evokes personality associations—that is, a color‐personality association (CPA). This study aims to propose a method for quantifying the relationships between color attributes and CPAs for single colors. Specifically, we first collected the CPAs of five traits evoked by single colors (i.e., extraverted–introverted, moody–unemotional, agreeable–disagreeable, organized–disorganized, and wide interests–narrow interests) in a carefully controlled experiment. Then, multiple linear regression (MLR) analyses were adopted to predict these CPAs based on three color attributes (lightness, chroma, and hue). Our results showed that (1) the personality associations could be evoked by colors and perceived consistently by observers; (2) the relationships between the color attributes and the CPAs could be well quantified by separately conducting MLR analyses in different regions of hue (i.e., red, green, blue, and yellow regions); and (3) both lightness and chroma were significant predictors in almost all predictive models and they might have different relative importance or directions of effect when predicting the CPAs in different regions of hue, even for the same trait. This study improves the understanding of how color evokes personality associations and takes the first step toward developing the method for predicting the CPAs for multicolor combinations. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 388–396, 2017     

Color associations with different building types: An experimental study on American college students

This study examines individuals' color associations with different building types (i.e., residences, schools, official buildings, hospitals, shopping malls, entertainment buildings, restaurants, hotels, factories, and religious buildings) and the reasons given behind their color choices. Ninety‐eight college students at a public institution in the southeast region of the United States participated in the study. Results indicate that color associations seem to be based on individual and emotional aspects where previous knowledge and experience with a particular building type play an important role. The reasons for color‐building associations are discussed and future research areas are suggested. © 2005 Wiley Periodicals, Inc. Col Res Appl, 31: 67–71, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20174     

Chromatic adaptation by illuminant matrix products: An alternative to sharpened von kries primaries

Previous attempts to predict chromatic‐adaptation correspondence have led to a sharpening dilemma—i.e., Von Kries primaries are chosen that do not include in the positive octant all the realizable (x,y) chromaticities. This leads to paradoxical adaptation predictions for the colors that have negative Von Kries coordinates. A solution is proposed here that expresses the asymmetric‐matching relation of chromatic adaptation as the product of two matrix transformations, given source illuminant 1 and destination illuminant 2: from source tristimulus values via adaptation matrix 1 to the adapted state coordinates, and from the adapted state via the inverse of adaptation matrix 2 to the destination illuminant tristimulus values. To avoid the sharpening instability, the entire spectrum locus must lie within the positive octant of the adapted state tristimulus space. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 275–278, 2014; Published Online 14 March 2013 in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/col.21799     

Interobserver variability and color representation systems

A systematic method of analyzing the colorimetric behavior of a set of observers is proposed. The differences between each observer and a standard one are analyzed with different procedures in two color‐representation systems. It is apparent that these differences strongly depend on the color‐representation system in which they are analyzed. Results obtained in this work indicate that comparison between two observers should be carried out by applying an optimized operator. This operator minimizes the differences between the color‐representation systems associated with the observers that are compared. The proposed method should be applied when color‐matching properties of a set of observers, or when color matching obtained with different colorimetric instruments, are compared. © 2002 Wiley Periodicals, Inc. Col Res Appl, 28, 15–24, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.     

Color vision assessment‐3. An efficient,two‐step,color assessment protocol

Color vision tests and multi‐test protocols in current use often fail to detect small changes in red/green (RG) and yellow/blue (YB) color vision due to poor sensitivity. The tests also have low specificity. In this study, we examine how improved understanding of within‐ and inter‐subject variability in RG and YB color vision and accurate assessment of the differences in color thresholds between the least‐sensitive, age‐matched normal trichromats, and the least‐affected deutans and protans can be used to design an efficient color vision screener (CVS) test. To achieve this objective, we examined two extensive data sets from earlier studies and carried out new experiments to provide better estimates of within‐subject variability in color thresholds and to validate the CVS test. The data sets provide essential information on inter‐subject variability, the effects of normal aging on RG and YB thresholds, and the spread in RG color thresholds in deutan and protan subjects. A statistical model was developed to optimize the parameters of the CVS test and to predict the limits of what can be achieved in color assessment. The efficiency and repeatability of the CVS test were then assessed in 84 subjects. The results match model predictions and reveal close to 100% test efficiency. The test takes between 140 and 160 seconds to complete and has close to 100% repeatability. An efficient, “two‐step” protocol based on the initial use of the CVS test followed by full color assessment in only those who fail the CVS test is also described.     

Color harmony in two‐piece garments

Using a categorical scale of 10 U, we have assessed color harmony in two‐piece garments (jackets‐trousers) considering a vicenarian and a quinquagenarian style. The experiment was performed by a panel of 59 Chinese observers (26 males and 33 females) with normal color vision and ages ranging 20–78 years, considering 300 color combinations for each of the two styles. For a given color combination, comparing results in the vicenarian/quinquagenarian styles for female/male observers, and observers below/above 45 years old, we found generally higher harmony scores for the vicenarian style, male observers, and observers older than 45 years. We found statistically significant differences (Welch two‐sample t test, P < 0.001) between color‐harmony results for the vicenarian and quinquagenarian styles, as well as considering the scores reported both by male/female observers and by observers below/above 45 years old. We propose a very simple lineal model fitting our current results with an average root mean square error (RMSE) of 0.70 U in our 10‐unit scale, which is below the one achieved by other complex models previously proposed, and also below the inter‐ and intra‐observer variability in our experiment. From our total experimental results, each of the five traditional color‐harmony principles (complementary hues and equal lightness, chroma, tone, and hue) was found to be valid at a low percentage (53–58% of the cases). © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 498–511, 2017     

Recovering neugebauer colorant reflectances and Ink‐spreading curves from printed color images

Spectral reflection prediction models, although effective, are impractical for certain industrial applications such as self‐calibrating devices and online monitoring because their calibration requires specific color‐constant calibration patches. Using the CMYK Ink‐Spreading enhanced Yule‐Nielsen‐modified Spectral Neugebauer model (IS‐YNSN), we propose a method to recover the colorant reflectances (Neugebauer primaries), the ink‐spreading curves, and the Yule‐Nielsen n‐value using only tiles extracted from printed color images. There is no prior knowledge about the reproduction device. Thanks to a set of constraints based on principal component analysis and the relationships between composed Neugebauer primaries and the ink transmittances, good approximations of the Neugebauer primaries are achieved. These approximations are then optimized, yielding an accurately calibrated IS‐YNSN model comparable to the one obtained by classical calibrations. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 216–233, 2014; Published online 23 February 2013 in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/col.21800     

Helical structure of complementary colors' relative spectral distribution function

I report a curious double helix in psychophysical data. As recently reported, color complementarism structures at least 40 functional roles in vision including all Red‐, Green‐, Blue‐peaked functions (e.g., color matching functions, Helmholtz–Kohlrausch effect, saturation discrimination, lightness discrimination, and wavelength discrimination). These can be modeled from the relative spectral power distribution (SPD) function of complementary colors (at requisite power ratios to neutralize complements). So, the SPDs three‐dimensional (3D) structure is of interest. Extended to the hue cycle, the SPD is plotted in a rectilinear graph of wavelength versus wavelength with radiance vertical to the plane. In this rectilinear color mixture space, the white locus representing the illuminant chromaticity is not a single point (representing the junction of complementary pairs of wavelengths) but a sinusoidal curve whose 3D structure is a double helix, representing an SPD and its complementary SPD. The structure's purpose is possibly to store and access global complementary colors data across illuminants. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 292–296, 2013     

Optimization of color‐representation systems when comparing different observers

Due to the variability in the sets of color‐matching functions, different real observers have associated different color‐representation systems. This fact darks the true interpretation of the experimental results obtained for different observers. In this work, we propose a transforming operator, which optimizes the mapping of the color‐representation system associated with an arbitrary observer into the system spanned by a standard set of color‐matching functions. When comparing the experimental results for different observers, this transformation allows us to obtain more reliable conclusions. If the the data are analyzed in the systems obtained by applying the optimized operator, the differences between the colorimetric behavior of two real observers are less than when, as usual, the results are compared in the systems spanned by the sets of color‐matching functions of the individual observers. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 416–423, 2000     

Color changes in cyanosis and the significance of congenital dichromasy and lighting

There are anecdotal reports of color vision deficient medical practitioners (particularly deuteranopes) having difficulty in recognizing cyanosis. An understanding of the color changes in oxygenated blood has led to a better understanding of the lighting needs for hospitals. Using the same database, this article investigates the propensity for color vision deficient observers to make mistakes with cyanotic patients. The possibilities for helping the observer with appropriate color of lighting are considered. The spectral reflectances of blood at varying oxygenation levels previously reported were used 7 ; 8 to calculate chromaticity and lightness. The direction of the chromaticity change was compared with the protanopic and deuteranopic confusion lines. An attempt was made to identify sources that enhanced color changes for the color deficient. The color change of blood oxygenation is closely aligned with the confusion lines of congenital dichromats (particularly protanopia) showing the potential for difficulty in making this decision. No source could be demonstrated to solve the problem or even reduce it significantly. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 428–432, 2007     

Theoretical considerations on small color differences ascribed to the standard observer made on the basis of individual color‐matching functions

An analytical method to determine how color‐matching functions influence the perception of chromaticity differences is proposed. We show that, as a consequence of the observer metamerism, a metameric color‐match perceived by one observer may appear to be a significant mismatch to a different observer. It is also shown that, on average, the differences between the color‐matchings made by two different observers can be estimated to be in the order of 2 CIELAB units. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 194–200, 2009     

Chromatic luminance,colorimetric purity,and optimal aperture‐color stimuli

Chromatic luminance (i.e., luminance of a monochromatic color) is the source of all luminance, since achromatic luminance arises only from mixing colors and their chromatic luminances. The ratio of chromatic luminance to total luminance (i.e., chromatic plus achromatic luminance) is known as colorimetric purity, and its measurement has long been problematic for nonspectral hues. Colorimetric purity (p_c) is a luminance metric in contrast to excitation purity, which is a chromaticity‐diagram metric approximating saturation. The CIE definition of p_c contains a fallacy. CIE defines maximum (1.0) p_c for spectral stimuli as monochromatic (i.e., optimal) stimuli, and as the line between spectrum ends for nonspectrals. However, this line has <0.003 lm/W according to CIE colorimetric data and is therefore effectively invisible. It only represents the limit of theoretically attainable colors, and is of no practical use in color reproduction or color appearance. Required is a locus giving optimal rather than invisible nonspectral stimuli. The problem is partly semantic. CIE wisely adopted the term colorimetric purity, rather than the original spectral luminance purity, to permit an equivalent metric for spectrals and nonspectrals, but the parameter of equivalence was never clear. Since 1 p_c denotes optimal aperture‐color stimuli for spectrals, arguably 1 p_c should denote optimal stimuli consistently for all stimuli. The problem reduces to calculating optimal aperture‐color stimuli (“optimal” in energy efficiency in color‐matching) for nonspectrals, shown to comprise 442 + 613 nm in all CIE illuminants. This remedy merely requires redefinition of 1 p_c for nonspectrals as the line 442–613 nm, and gives meaningful p_c values over the hue cycle allowing new research of chromatic luminance relations with color appearance. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 469–476, 2007