Showing papers in "Color Research and Application in 1997"

How the CIE 1931 color-matching functions were derived from Wright-Guild data

Abstract: The principles that guided the founders of the CIE 1931 system for colorimetry are examined. The principles are applied to the Wright-Guild experimental determinations of the color mixture data to show in detail how and why each step in the development of the CIE 1931 system for colorimetry came about. These steps are examined in the light of 65 years advanced knowledge of colorimetry. The necessity for each of these principles in the modern world is examined critically to determine whether one might hold to the same principles if the system were being freshly formulated today. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 11–23, 1997.

Chroma variations and perceived quality of color images of natural scenes

Abstract: Transformations of natural images in the per- ulated with respect to luminance and chromaticity in order ceptually uniform CIELUV color space have been investi- to improve the display of color. Usually, some implicit gated with respect to perceptual image quality. To this assumptions are made to limit the almost infinite number end, digitized color images of four natural scenes were of possible manipulations. One of these assumptions is described on the basis of their color point distributions that only global changes need to be considered. This stems in the CIELUV color space. A new set of images was from the notion that images are coherent in the sense that created by varying the chroma value of each pixel while different parts of the same image share luminance and the lightness and hue angle were kept constant. The spectral properties due to the fact that they belong to the chroma was changed in two different ways: (1) through same object or are illuminated by the same light source. the addition or subtraction of the same amount of chroma This assumption underlies global reproduction techniques to or from the chroma value of each pixel; (2) through in which the same color operation is applied to all pixels, multiplication of the chroma value of each pixel by a irrespective of the content of the image. 1,2 Another as- constant. In three experiments, subjects judged the per- sumption is that the optimum image equals the original ceptual quality, colorfulness, and naturalness of the im- ( real-life ) scene. Hence, all efforts should be directed ages on a ten-point numerical category scale. The results towards finding ways of approaching this equality as indicate that colorfulness is the main perceptual attribute closely as possible. underlying image quality when chroma varies. Colorful- In this article, a different constraint on color reproduc- ness itself was found to depend on both the average tion is proposed, namely, the experienced naturalness of chroma and its variability. In general, the subjects pre- an image. This choice is motivated by the argument that ferred slightly more colorful images to the original ones. constraints should be formulated not in the physical, but The perceptual quality of the images was found to be in the psychological domain, the reason being that image closely related to the naturalness of the images.q 1997 quality judgments are based on a comparison between the

Impact of Three Interior Color Schemes on Worker Mood and Performance Relative to Individual Environmental Sensitivity

Abstract: Effects of three office color schemes (red, blue- made environment has been meeting our basic shelter needs for centuries. Today, buildings serve other pur- green, and white) were examined for 90 workers' mood and productivity, taking into account individual differ- poses, such as education, entertainment, and work activi- ties. Even with an affinity for nature, it has become in- ences in environmental sensitivity (high screeners vs. low screeners). Matched on relevant variables, subjects were creasingly important to realize that individuals exist within enclosed structures for most of their lives. There- assigned to one of three offices. Workers performed office tasks for 4 consecutive workdays. Workers in the red fore, understanding how spaces affect individuals is nec- office reported more dysphoria than workers in the blue- essary for personal well-being. Perhaps, most important green office. Low screeners reported more dysphoria in are the effects of the work environment, the place where the red and white offices than high screeners. High individuals spend most of their waking hours. screeners performed better on office tasks in the red office This research was begun with the hope of being able to and poorer in the blue-green office than low screeners. understand more fully how color within the work environ- The results for performance are discussed as an extension ment affects worker mood and performance. The purpose of the Yerkes-Dodson principle, while the results for was to determine the effects of three different interior color mood tended to support previous findings. q 1997 John schemes on mood, speed, and accuracy on proofreading

Suprathreshold color‐difference ellipsoids for surface colors

Abstract: The RIT-DuPont visual color-difference data [Color Res. Appl. 16, 297–316 (1991)] have been used to estimate contours of equal color-differences (ellipsoids) at 19 color centers, in CIELAB and x, y, Y/100 color spaces. The ellipsoid fits are better in the CIELAB space than in x, y, Y/100, since the design of the RIT-DuPont experiment emphasized directional balance in CIELAB. The ellipsoids estimated are hardly tilted with respect to L* or Y/100, and they appear to be in overall good agreement with those reported for object colors in recent publications. From the characteristics and accuracy of the RIT-DuPont experiment, the current ellipsoids can be considered highly reliable and representative of color discrimination under the observational conditions employed, these closely following the “reference conditions” recently suggested by the CIE for industrial color-difference evaluation [Color Res. Appl. 20, 399–403 (1995)]. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 148–155, 1997

Simple estimation methods for the Helmholtz—Kohlrausch effect

Abstract: Four kinds of simple estimation equations are proposed for the Helmholtz—Kohlrausch effect. Two of them can be used for luminous colors, and the other two for object colors. In each of luminous and object colors, the two estimation equations are given to each of the Variable-Achromatic-Color (VAC) and the Variable-Chromatic-Color (VCC) methods. All the equations are similar in type to the Ware—Cowan equation. They give the ratio between luminance (or metric lightness) of test color stimulus and its equivalent luminance (or equivalent lightness) directly. Though their computations are simple, they can apply to various H—K effects including their adapting luminance dependency. The applicable fields of the proposed equations are wider than those of the Ware—Cowan equation. The proposed equations can be applied to predict the H—K effect within the whole chromaticity gamut including spectral colors, spectral luminosity functions based on direct color matching from 0.01 Td to 100 000 Td using the photopic and the scotopic spectral luminosity functions specified by CIE, equivalent lightness values of NCS colors, and others. © 1997 John Wiley & Sons, Inc. Col Res Appl. 22, 385–401, 1997

Color meaning and context : comparisons of semantic ratings of colors on samples and objects

Abstract: This article reports the results of a study comparing semantic ratings of color samples (chips) with those of the same colors applied to a variety of familiar objects. Subjects rated a set of 13 color chips and 5 sets of objects, each appearing in the same 13 colors, against 5 bipolar, 7-step semantic differential scales. The scales consisted of beautiful-ugly, elegant-vulgar, loud-discreet, masculine-feminine, and warm-cold. Analyses performed on the data indicated that generally few significant differences existed between chip and object ratings for the same color; when such differences existed, the chip was always rated more beautiful, elegant, discreet, feminine, and warm than the object; and differences between chip and object ratings were confined primarily to a limited number of colors, objects, and semantic scales. The results of this study have implications for the use of color chips in color planning and for the generality of results of earlier color meaning research. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 40–50, 1997.

Observer variability in metameric color matches using color reproduction media

Abstract: Standard color-matching functions are de

Error propagation analysis in color measurement and imaging

Abstract: We apply multivariate error-propagation analysis to color-signal transformations. Results are given that indicate how linear, matrix, and nonlinear transformations influence the mean, variance, and covariance of color-measurements and color-images. Since many signal processing paths include these steps, the analysis is applicable to color-measurement and imaging systems. Expressions are given that allow image noise or error propagation for a spectrophotometer, colorimeter, or digital camera. In a computed example, error statistics are propagated from tristimulus values to CIELAB coordinates. The resulting signal covariance is interpreted in terms of CIELAB error ellipsoids and the mean value of color-difference measures, and . The application of this analysis to system design is also illustrated by relating a tolerance to equivalent tristimulus-value error statistics. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 280–289, 1997

A generic approach to color modeling

Abstract: Color modeling defines the relationships between colorants, their mixtures, and their resulting spectral and colorimetric properties. A “colorant” can refer to a dye, pigment, or ink, as well as chromatic lights used in various display technologies. Computer colorant formulation systems are an embodiment of the color modeling of materials such as textiles, plastics, and paint. Color management systems for imaging applications exploit color models of CRT displays, photographic materials, and printers. The literature on modeling material and imaging systems tends to be segregated. In the process of teaching color modeling, common methodologies and theories have emerged leading to a “generic” approach. All of these systems can be modeled using two basic stages. The first stage consists of defining a spectral description where colorants and their mixtures can be described using linear algebra. The second stage defines the relationship between “user controls” and the scalars associated with the linear description of each colorant where the user control may be digital counts, volumetric or gravimetric concentration. The commonalities between characterizing the colorimetry of computer-controlled CRT displays and computer colorant formulation are presented. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 318–325, 1997

Calculation of color gamuts based on the Neugebauer model

Abstract: The calculation of color gamuts is often based on transforming the colorant boundaries to color space. This method works for “well behaved” processes, but in some cases it is necessary to take into account not only these physical boundaries, but also other kinds of boundary surfaces. These additional boundaries are introduced here for 3-ink and 4-ink processes and are called natural and hybrid boundaries. Examples of print processes for which these different kinds of boundaries should be taken into account are given for the Neugebauer and localized Neugebauer model. Finally, an analytical approach is presented for the calculation of color gamuts of “well behaved” processes based on the Neugebauer model. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 365–374, 1997

Some aspects of the visual scaling of large colour differences

Abstract: The formulation of a metric to provide numbers that correlate with visually perceived colour differences has proved a very difficult task. Most early experimental work was concerned with just-perceptible colour differences. Later the concept of perceptibility was expanded to acceptability, it being argued that many industrial tolerances were larger than just-perceptible. This led naturally to the concept of large colour differences and the question as to whether the current CIE colour-difference formulae, specified as appropriate for just-perceptible differences, can be applied to larger differences than those concerned with, for instance, colour matches experienced in the fabric dyeing industry. This article investigates the application of four colour-difference formulae to visual scaling of large colour differences between photographically prepared reflection colour samples at approximately constant lightness. It is shown that the scaling of colour differences depends on the directions of hue and chroma differences of a test sample when compared with a reference. It is also shown that, of the four candidate colour-difference metrics, the modified CIE 1976 L*a*b* colour difference, referred to as CIE1994 or , correlates best with visual scaling. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 298–307, 1997

Testing five color‐appearance models for changes in viewing conditions

Abstract: Five color-appearance transformations were compared in a series of psychophysical experiments under a variety of viewing conditions. These transformations included the Hunt model, the Nayatani model, RLAB, CIELAB color space, and von Kries chromatic adaptation. Observers compared original printed images viewed under one set of viewing conditions to reproductions viewed on a monitor with differing conditions. These conditions varied in white point, luminance level, background reflectance, and surround. Reproductions were produced using the various color-appearance models and observers decided which reproduction was the closest match to the original. RLAB was found to produce the most acceptable reproductions, except for changes in surround. CIELAB and von Kries adaptation also performed well. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 165–173, 1997.

Gamut mapping from below: Finding minimum perceptual distances for colors outside the gamut volume

Abstract: A colorimetrically characterized computer-controlled CRT display was used to determine closest perceptual color matches of 25 colors when an exact match was not allowed. An artificial but realistic color gamut was created by intersecting the display gamut with a gamut of a Xerox 4920 color laser printer. Each of 21 observers performed color matches between out-of-gamut colors and those on the artificial gamut's edge. Each observer made color matches on 4 different images. The images represented some of the categories that business graphic images can fall into. Between the different image types, there were no multidimensional (MANOVA) statistically significant differences at the 10% confidence level in any of the 25 colors tested. The mapping vectors showed that (1) observers don't make simple matches as assumed by most gamut-mapping experiments done to date, (2) the influence of image content for simple graphical images tested does not have a large effect when the task is to make closest perceptual color matches, and (3) CIELAB hue angle is not uniform enough, especially in blue and cyan regions, to make adequate gamut-mapping transforms. A simple model for clipping type gamut mapping is proposed. Results are compared to predictions of a new gamut-mapping technique that minimizes weighted color difference between the target color and the gamut boundary. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 402–413, 1997

Preference for Japanese complexion color under illumination

Abstract: To find the chromaticity coordinates of the “Preferred Complexion of Japanese Woman” under illumination, subjective estimation experiments were conducted on the complexions of 3 female models under each of 40 colors of illumination. The chromaticity coordinates of “Preferred Complexion” for each model were about the same together. The average chromaticity coordinates of 3 female models were (u′, v′) = (0.2425, 0.4895) under the standard illuminant D65. The “Preferred Complexion of Japanese Woman” in this experiment was compared with the “Preferred Complexion of Caucasian Woman” studied by Sanders. The “Preferred Complexion of Japanese Woman” was shifted to a slightly higher saturation and reddish in hue, compared with the actual complexion of “Japanese Woman.” On the other hand, the “Preferred Complexion of Caucasian Woman” was orange in hue, the same as the actual complexion of “Caucasian Woman.” The color shift of saturation of the “Caucasian Woman” was 3.5 times as large as that of the “Japanese Woman.” © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 269–274, 1997

An abridged technique to diagnose spectrophotometric errors

Abstract: The effect on colorimetric accuracy of spectrophotometric errors (±0.5 and ±1% reference white, ±0.25 and ±0.5% reference black, and ±0.5 and ±1 nm wavelength) was simulated for the BCRA Series II tile set by using previously investigated models for these errors. ΔE*94 color differences of up to 5.2 could result. Because the errors are linearly related to CIELAB differences for each tile, a technique was derived that enabled ΔL*, Δa*, and Δb* coordinates between a calibrated tile and its measured value to be transformed into estimates of reference white, reference black, and wavelength error. The cyan tile was identified as the most effective tile for this technique. “Universal” equations are included for 45/Normal and Normal/Total geometries traceable to the National Institute of Standards and Technology (NIST), and Normal/45, Normal/Total, and Normal/Diffuse geometries traceable to the National Physical Laboratory (NPL). Measuring the cyan tile on a regular basis and transforming its colorimetric coordinates into spectrophotometric error metrics provides a useful method to validate the accuracy and reproducibility of a color-measurement instrument. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 51–60, 1997.

A simple estimation method for effective adaptation coefficient

Abstract: A method was proposed in a previous article (CRA, 22, 240–258, 1997) to estimate the state of incomplete adaptation by using the effective chromatic adaptation coefficient αmin The method could be applied to any experiment on chromatic adaptation using object-color or luminous-color stimuli, but its computational procedure was rather tedious For this reason, the two simple methods, Methods I and II, are proposed to give the approximate estimates of αmin Method I uses the corresponding reference color under reference illuminant to a test achromatic color under test illuminant Method II uses the two kinds of relation equations between test adapting luminance and αmin The estimates of αmin by each of the two methods agree fairly well with those given in the previous article to the three experiments studied © 1997 John Wiley & Sons, Inc Col Res Appl, 22, 259–268, 1997

Prediction of absorbance from reflectance for an absorbing-scattering fabric

Abstract: Beer's law of light absorption and the Kubelka-Munk analysis are applied to absorbing-scattering fabric. A relation between the Kubelka-Munk function F(R) and the absorbance of dyed fibers is proposed. The relation is used to predict the absorbance of a colorant from the reflectance of a substrate dyed with it. Samples of polyester fibers dyed with different colorants are used. The predicted absorbances of these samples agree fairly well with those measured directly on the spectrophotometer. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 32–39, 1997.

Color changes in the surface of granitic materials by consolidated and/or water repellent treatments

Abstract: Color is one of the parameters to be monitored when determining the suitability of a protective or conservative treatment of stone. Application of a given treatment product should elicit the least possible effect in this parameter. Changes in color of five varieties of granite of highly varying characteristics due to their origin are studied in the present work. All the granites studied are widely used in buildings of historical interest in Avila (Spain). Some varieties are from unaltered facies (grey granites of different grain size), and have a very low degree of porosity, while other are from facies that have undergone strong natural weathering processes, and that display important mineralogical and physical changes. In this sense, the ochre variety of granite contains clays (smectite and some kaolinite); the white variety contains kaolinite and opal, and the red variety contains kaolinite, opal, and iron oxihydroxides. Fresh cut and artificially aged (with 25 cycles of freezing/thawing and cold/heat treatment) samples were treated with consolidant (RC80 or RC70) and/or water repellent (H224) agents. After the corresponding statistical treatment of data obtained, significant changes in ΔE were observed with the treatments given; such changes are more pronounced in unaged samples. Changes in ΔL (lightness), however, despite being noticeable, seem to have only a minor effect on ΔE, which seem to be more dependent on changes in Δa and Δb. This was more pronounced when the stone was treated with RC80 and then with H224. © 1997 John Wiley & Sons, Inc. Cal Res Appl, 22, 133–141, 1997

Basic Mandarin color terms

Abstract: In comparative studies of basic color terms of various ethnic groups, Berlin and Kay found that the number of basic color terms used is greater, the more highly developed a culture becomes and vice-versa (Berlin and Kay 1969: 16). According to their thesis, peoples possessing the most highly developed cultures use 11 basic color terms, or the equivalents of white, black, red, yellow, green, blue, brown, orange, purple, pink, and gray. These 11 color terms are found in Japanese, Korean, and Cantonese. However, as only six are found in Mandarin, Mandarin was assigned to a lower stage of cultural development. This is incorrect. In an effort to prove this assertion, this author has conducted numerous studies. Based on research of Mandarin color terms and mapping response, this study attempts to prove that Mandarin has long contained the 11 basic color terms noted by Berlin and Kay. However, after conducting a mapping response study, it was discovered that the Berlin-Kay color set (i.e., the Berlin-Kay-MacLaury Munsell set) is inadequate for examining low saturation basic color terms such as he (Br) and cang (grayish BG), the representative colors of which are difficult to fully ascertain. During this study, this author discovered a certain degree of difficulty hindering mutual understanding between Eastern and Western cultures. Consequently, this study seeks to promote a degree of such understanding. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 4–10, 1997.

Traffic signal light detection through sunglare filters of different q factors

Abstract: Recent guides for use of sunglare protection filters have introduced the concept of Q factors as a measure of colour appearance distortion in viewing traffic signal lights. The adoption of Q factor values was apparently arbitrary and not firmly based on experimental data. The manner in which changes in Q factor affect colour perception and detection of signal lights has been measured and shows that detection thresholds vary with the Q factor in a manner that can only partly be explained, but that is not independent of the colour of the signal as assumed in the guides. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 24–31, 1997.