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In a preceding study we measured human color constancy in experimental conditions in which simulated illuminants and surface colors were varied in the chromatic domain only. Both illumination level and sample reflectance were fixed in that study. In the present study we focus on the achromatic dimension, both with respect to luminance contrast (Experiment 1) and overall illumination (Experiment 2). Sample‐to‐background contrast was varied over a two log unit range that covered both luminance decrements and increments. Illumination level was varied either for the short‐wave‐sensitive (S) cones only or for all three cone types simultaneously. Data predictions on the basis of a cone‐specific response function, derived in our preceding study, indicate that this model has difficulty in accommodating the results obtained with varying luminance contrast. However, a modified version of the response function, incorporating separate processing of color and luminance contrast, correctly predicts the data from both the present and the previous study. We also show that over a limited stimulus range our earlier response function is mathematically equivalent to Jameson and Hurvich's model of brightness contrast. The latter model, cast into a trichromatic format, performs equally well or better than our original response function, but is less accurate than our modified model. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 172–185, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20105 相似文献
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Over time, much work has been carried out to ascertain the validity of Grassmann's laws, Abney's law, CIE standard color‐matching functions and, up to now, no definitive answer has been given. Some of the phenomena subject of this debate are considered. An apparatus for color matching in 1.8° visual field has been realized with two sets of primary lights with broad spectral bands. This kind of primaries is the great difference with respect to other laboratories because it allows an indirect check of the Grassmann additivity law on the basis of the spectra and individual color‐matching functions by evaluating: (1) the tristimulus values of the primary lights; (2) the transformation matrices between the two reference frames defined by the two primary sets; and (3) the tristimulus values associated to all the pairs of matching lights in the bipartite field produced in the evaluation of the two sets of color‐matching function. The discrepancies of the data resulting in the check (1) and (2) are all compatible with the range defined by the uncertainty propagation of the individual color‐matching functions. In the check (3) fifteen tristimulus values over 18 have a discrepancy lower than one standard uncertainty. Grassmann's proportionality law is checked directly by reducing the matching lights with a neutral filter and holds true. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 271–281, 2008. 相似文献
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Robert Sève 《Color research and application》2018,43(5):726-735
This publication describes a work related to the French language, for assigning a color name to an object whose colorimetric characteristics have been measured. This is the subject of a recently published book. The work is the result of an old publication by Afnor, the French standardization organization, work unfortunately obsolete by its colorimetric part. This publication describes the work that has been done to update it and make it convenient to use. The present text, by publishing some of the tables and graphs of the French book, presents the work done in French by a method that differs from that used by Kelly and Judd years ago. 相似文献
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Kenjiro Hashimoto Tadashi Yano Masanori Shimizu Yoshinobu Nayatani 《Color research and application》2007,32(5):361-371
“Visual clarity” or “feeling of contrast” of object colors under illumination is affected significantly by changing color‐rendering property of light source used. Though the feeling of contrast is considered one of the most important characteristics on color‐rendering properties of light sources, it cannot be estimated adequately by using the present Ra method. The new index FCI is proposed for estimating the effect of feeling of contrast quantitatively under any light sources. The FCI is derived using a simple transformation of the gamut area, which is constituted by a specially selected four‐color combination in CIE LAB color space. The FCI correlates well with the illuminance ratio for equal feeling of contrast (or equal visual clarity) on various light sources reported so far. Using the FCI together with the present CIE Ra, the color‐rendering capability of a light source can be well clarified. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 361–371, 2007 相似文献
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The nonlinear relationship between luminance and DAC count could be characterized with the simplified model, if optimum brightness level is set. In this study, we propose a technique to set the optimum level of brightness, in which offsets for RGB channels can be assumed to zero, and determine the gamma coefficients from log–log data without nonlinear optimization. The optimum brightness level could be found by measuring a few tones of neutral for the combination of 3 levels of brightness and 2 levels of contrast. This technique has two advantages. It does not require measurements for 0 DAC count, and does not require nonlinear optimization in finding the gamma coefficient of the display system. Two CRT monitors by different manufacturers have been tested. As the result, all monitors could be set to their optimum state with a different combination of brightness and contrast. In that state, the gamma coefficient for each channel could be determined from two measuring data and the tone reproduction characteristics of the RGB channel could be characterized with the simplified equation, neglecting offset and gain. The accuracy of characterization was better than 0.5 ΔE*ab for 125 colors for a monitor having good channel independence. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 408–415, 2000 相似文献
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This study looks at the perceived quality of light‐emitting diode (LED)‐based lighting of various colors. The objective was to find out whether LEDs could provide better (i.e., more relevant and acceptable) lighting than that which is obtained with standard halogen or fluorescent sources. The perception of objects was assessed under different lighting schemes. Subjects were invited to add red, cyan and/or amber to white LED‐based light to match the halogen and fluorescence rendering on specific targets: a color chart and a painting. They were also asked to rate the difference between the two, and to express their preference. The results obtained for the perception of LED‐based lighting were quite positive. Color blendings of LED light were found to provide illuminated situations similar to halogens or fluorescent sources. These blendings were well accepted, and indeed often preferred, although the color rendering index (CRI) was always low. This indicates that the CRI as it stands is inadequate to characterize the color rendering of solid‐state light sources, and needs to be updated. LED‐based lighting systems seem to have considerable potential for use in shops and display units, where they may well outperform existing lighting systems. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 310–320, 2009 相似文献
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The use of colorimetry within industry has grown extensively in the last few decades. Central to many of today's instruments is the CIE system, established in 1931. Many have questioned the validity of the assumptions made by Wright1 and Guild,2 some suggesting that the 1931 color‐matching functions are not the best representation of the human visual system's cone responses. A computational analysis was performed using metameric data to evaluate the CIE 1931 color‐matching functions as compared to with other responsivity functions. The underlying assumption was that an optimal set of responsivity functions would yield minimal color‐difference error between pairs of visually matched metamers. The difference of average color differences found in the six chosen sets of responsivity functions was small. The CIE 1931 2° color‐matching functions on average yielded the largest color difference, 4.56 ΔE. The best performance came from the CIE 1964 10° color‐matching functions, which yielded an average color difference of 4.02 ΔE. An optimization was then performed to derive a new set of color‐matching functions that were visually matched using metameric pairs of spectral data. If all pairs were to be optimized to globally minimize the average color difference, it is expected that this would produce an optimal set of responsivity functions. The optimum solution was to use a weighted combination of each set of responsivity functions. The optimized set, called the Shaw and Fairchild responsivity functions, was able to reduce the average color difference to 3.92 ΔE. In the final part of this study a computer‐based simulation of the color differences between the sets of responsivity functions was built. This simulation allowed a user to load a spectral radiance or a spectral reflectance data file and display the tristimulus match predicted by each of the seven sets of responsivity functions. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 316–329, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10077 相似文献
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In this research we compare the colorimetric behavior of several observers. For color centers recommended by CIE we have produced large sets of spectral distributions, which are metameric for the CIE 1931 standard observer. For each one of the color centers, we compare the clouds of chromaticity coordinates with the chromaticity thresholds. We define a parameter that provides a quantitative measure of the interobserver variability. This parameter is used to arrange the observers by their degree of likeness. A similar procedure has been used to compare two real observers. It is shown how there is no reciprocity between the colorimetric behavior of two real observers. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 262–269, 2001 相似文献
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In a text dating between 1259 and 1277, the Persian scholar al‐Tusi presented a systematic arrangement of 26 color terms. We propose a reconstruction of all color terms from al‐Tusi's scheme, in terms of preferred translation, mean CIEL*a*b* coordinates and digital representation. This reconstruction is based on a visual experiment with 30 subjects, who identified the Munsell chip best representing each color term. Persian words for which the meaning changed since the time of al‐Tusi were substituted by direct translations. The results show considerable interobserver variability in the colors selected when identifying color terms. This relatively large variation was shown to be a characteristic for memory matching experiments in general. Several specific color terms for which the resulting color variation was particularly large are discussed in more detail, and possible explanations for these variations are proposed. The proposed reconstruction suggests that al‐Tusi's list is largely consistent in modern colorimetric terms, although some large hue shifts are observed for color terms corresponding to green. We found no evidence for blue‐green (“grue”) confusion. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 206–216, 2016 相似文献
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Maria E. Nadal Edward A. Early Will Weber Robert Bousquet 《Color research and application》2008,33(2):94-99
The NIST 0:45 reflectometer measures the spectral reflectance factor at an influx angle of 0° and an efflux angle of 45° of colored, nonfluorescent specimens at room temperature, with widths ranging from 3 to 10 cm and heights from 3 to 20 cm and with an uncertainty of less than 0.5 in color difference units. Published in 2008 by John Wiley & Sons, Inc. Col Res Appl, 33, 94–99, 2008 相似文献
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In CRT monitor characterization accuracy is largely affected by the brightness setting on the monitor. At the optimum brightness level, which adjusts the offsets of RGB channels to nearly zero, CRT monitors have a simple relationship between DAC count and luminance so characterization can be achieved accurately. However, since the optimum brightness levels of CRT monitors are different from one another monitor users, have to make adjustments to the monitor themselves. In this study, a simple device named, brightness optimizer, is fabricated to determine the optimum brightness level objectively. This method uses change of curvature in tone reproduction curves plotted in log‐log scale, according to the changes of brightness level. In this article, the configuration of the brightness optimizer and the measurement processes are described. The repeatability and the accuracy in the measurement of the optimum brightness level for three different CRT monitors are also evaluated. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 468–472, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10199 相似文献
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A new method was used to characterize computer‐controlled liquid crystal displays (LCDs). The characterization, which was performed to enable colorimetric image display, included channel independence, spatial independence, screen uniformity, and colorimetry. The colorimetric model consisted of three one‐dimensional look‐up tables (LUTs) describing each channel's optoelectronic transfer function and a 3 × 4 matrix transformation that included black‐level flare. The matrix coefficients were estimated statistically by minimizing the average CIEDE2000 color difference for a data set sampling the display's colorimetric gamut. The LUTs were recreated dynamically throughout the optimization of the matrix coefficients. The characterization was implemented with three different instruments to evaluate the robustness of the method with respect to measurement uncertainty. The average performance ranged between 0.1 and 0.4 ΔE00 and was well correlated with instrument precision. The optimization approach improved performance by a factor of two compared with direct measurements. Despite differences in instrument design, the chromaticities of each primary following optimization and black‐level flare compensation were very similar. This excellent performance was a result of the display's optoelectronic properties well matching the model assumptions. The technique was also used to characterize three additional LCD displays ranging in their matching of the model assumptions. In this case, performance worsened. For one display, more complex models would be required for colorimetric characterization. Finally, a colorimetric characterization based on measurements at the center of the display and perpendicular to the face was used to predict measurements at the edges and at different angles. The results indicated that characterizations would be required at multiple positions and angles in order to achieve sufficient accuracy. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 365–373, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20046 相似文献
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Accurate colorimetry starts with accurate color matching functions (CMFs). Due to changes in the macular pigment and cone pigment optical densities at different retinal locations, different CMFs are required for different stimulus field sizes. To characterize the accuracy of the CIE recommendation for the use of 2° and 10° standard CMFs and the field-size dependent CIEPO06 model, in this study, a series of achromatic matching experiments were performed with 2°, 4°, 6°, 8°, and 10° bipartite fields using spectrally narrowband primaries. Using the CIEPO06 model, optimal field sizes were estimated that minimize the chromaticity differences between the spectrally narrowband observer matches and the spectrally broadband achromatic target. It was found that the optimal field size estimated using the CIEPO06 model is close to half the actual bipartite field size in most cases, except for the 2° field. The discrepancy between the 10° bipartite field in Stiles & Burch's experiments and our optimal field size (6.54°) was assumed to be due to different individual color comparison strategies. However, the results of experiments requiring specific observer gaze positions did not support this assumption and the reason for the discrepancy remains unclear. Confirming our earlier results, the primary set (636, 521, 447 nm) was again found to be largely insensitive to changes in CMFs and to provide the most accurate matches under various fields of view. The inter- and intra-observer variability ellipses for 2° matches are larger than those for 10°, consistent with Brown's finding for color discrimination ellipses. The magnitude of the intraobserver variability was similar for all field sizes, except for 2° field size, where matching errors were larger for some primary sets. 相似文献
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A CIELAB anomaly, in which smaller spectrophotometric errors at all wavelengths lead to larger CIELAB differences, is identified. It is shown that the reversal can occur throughout tristimulus space and is colorimetrically important during calibration procedures. Three numerical examples of the reversal, using data from the BCRA tiles, are given. The reversal cannot be attributed entirely to metamerism, which itself may cause large spectrophotometric error leading to small CIELAB difference. The effect is compounded by the nonlinearity of CIELAB relative to tristimulus coordinates. A recommendation for avoiding the reversal is offered. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 66–68, 2005; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/col.20076 相似文献
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Sets of color tiles are available from the National Institute of Standards and Technology calibrated using the NIST 0:45 Reflectometer. The uncertainties associated with the measured values for the color tiles are an indispensable component of the calibration report that accompanies these tiles. A systematic, analytical approach developed previously was applied to the particular case of the reference instrument and color tile set, taking into account the operation and characteristics of the instrument and the spectral properties of the set. The primary sources of uncertainty were identified, and the resulting uncertainties in the color space values L*, a*, and b* were determined. In general, the uncertainties are lowest for those color tiles whose reflectance factors are nearly constant with wavelength. Published in 2008 by John Wiley & Sons, Inc. Col Res Appl, 33, 100–107, 2008 相似文献
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The primary goal of a color characterization model is to establish a mapping from digital input values di (i = R,G,B) to tristimulus values such as XYZ. A good characterization model should be fast, use a small amount of data, and allow for backward mapping from tristimulus to di. The characterization models considered here are for the case of an end user who has no direct knowledge of the internal properties of the display device or its device driver. Three characterization models tested on seven different display devices are presented. The characterization models implemented in this study are a 3D look up table (LUT) (Raja Balasubramanian, Reducing the Cost of Lookup Table Based Color Transformations, Proc IS&T/SID 7th Color Imaging Conference 1 ), a linear model (Fairchild MD, Wyble DR. Colorimetric Characterization of the Apple Studio Display (Flat Panel LCD). Munsell Color Science Laboratory Technical Report, 1998), and the masking model (Tamura N, Tsumura N, Miyake. Masking Model for accurate colorimetric characterization of LCD. Proc IS&T/SID 10th Color Imaging Conference 3 ). The devices include two CRT monitors, three LCD monitors, and two LCD projectors. The results of this study indicate that a simple linear model is the most effective and efficient for all devices used in the study. A simple extension to the linear model is presented, and it is demonstrated that this extension improves white prediction without causing significant errors for other colors. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 438–447, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col. 相似文献