Chromaticity changes of inorganic pigments in Chinese traditional paintings due to the illumination of frequently‐used light sources in museum

Optical radiation can cause permanent damage to the color of Chinese traditional paintings, which have extremely high responsivity in the museum illumination. In order to obtain quantitative influence laws of artificial illumination on inorganic pigments in Chinese traditional paintings and provide basis for choosing light sources, a long periodic illumination experiment was carried out to examine how prolonged exposure of three light sources (tungsten halogen, metal halide and white light emitting diodes), frequently‐used in museums, affect the chromaticity of five inorganic pigments [azurite (blue), cinnabar (red), orpiment (yellow), ancient graphite (black), clam shell powder (white)], commonly used in Chinese traditional paintings. Through the experiment, we found that the illumination causes a color change to inorganic pigments, and the degree of which is related to the photochemical stability of pigments and the high energy shortwave radiation in the light source spectrum. We also obtain the color change laws of the five pigments and the quantitative relationships of color damage for different painting types. These results can provide data basis for related research on Chinese traditional painting illumination and choice basis for light sources in museum lighting designs.     

“纸绢釉”的研制及其在宋风瓷画创作中的应用

"纸绢釉"是一种经高温烧成能呈现出陈年宣纸或绢布状的棕褐色系泛轻微点状机理的新釉料,烧成后其丰富的机理纹优于单色釉的单一色彩质感,又优于普通颜色釉无法在釉下再做绘画装饰的特性,整体色系质感十分适合表现宋画风格的陶瓷艺术作品,用纸绢釉表现的艺术作品其特点在于融合了对传统宋画的传承和创作者自身的审美素养以及当前时代背景下的文化精神,实现了一种独特的宋风美学样式,也表达了当代艺术创作者对于传统与创新的更深层次的审美理解和艺术追求。     

Daytime colorimetry of retroreflective materials

The daytime color of retroreflective materials is a mixture of sensations caused by diffusely reflected light plus a small amount of retroreflected light, the exact mixture depending on the illumination geometry and the goniophotometric characteristics of the material. The most nearly comparable results of color measurement can be obtained with instruments having 45°/0° geometry instead of sphere geometry. Spectrophotometers or colorimeters can be used. The calibration of these instruments is discussed. Most specifications for the daytime color of retroreflective materials call for the use of CIE standard illuminant D₆₅. However, one can use colorimeters designed to give color coordinates for illuminant C provided that color standards calibrated for D₆₅ are used.     

New method for specifying color‐rendering properties of light sources based on feeling of contrast

“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 R_a 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 R_a, the color‐rendering capability of a light source can be well clarified. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 361–371, 2007     

喷墨打印和喷墨印花用染料和有机颜料的进展

本篇是关于喷墨打印和喷墨印花用染料和有机颜料的综述文章。主要论述了用于纸张打印水性墨水的颜料和染料、纤维素纤维喷墨印花用活性染料、丝绸喷墨印花用酸性染料以及聚酯纤维喷墨印花用分散染料的进展情况。给出了组成各种墨水的典型配方。并预测了未来可能的发展趋势。     

A note about the abnormal hue angle change in CIELAB space

Liu et al. [Color Res Appl 1995;20:245–250] compared the CIELAB hue angles under CIE illuminants D65 and A for quantifying the color appearance changes for gem materials. They found that CIELAB hue angle for some gem materials under illuminant D65 was larger than under A, which is contrary to the perceived blue and purple appearances under daylight and incandescent light sources, respectively. They called this phenomenon as the abnormal hue angle change in the CIELAB space for the gem materials. In this article, we note the proper way to quantify the appearance changes is to use chromatic adaptation transforms (CATs), since we are only concerning the color change of the illumination. At the same time, it is found that the chromatic adaptations in the sharper sensor space and in the cone fundamental space provide different results, the ones related to the latter being in better agreement with current blue‐to‐purple color appearance change. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 322–327, 2013     

Suitability of Printing Materials for Heat-Induced Inkless Eco-Printing

Pyrolysis volatiles and the environmental impact of printing paper, newspaper, and silk were investigated to identify suitable materials for heat-induced eco-printing (HIEP) using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Furthermore, the printing effects of simulated HIEP and the material microstructures were studied using scanning electron microscopy (SEM). The results indicated that the toxicity of pyrolysis volatiles is highest for newspaper, followed by silk and then printing paper, whereas environmental friendliness follows the opposite trend. A high concentration of lignin, the basic structural element of which is phenyl propane, and the presence of halogens in the newspaper led to the generation of more toxic substances during the pyrolysis process. The benzene compounds and heterocyclic compounds in silk also produced high levels of toxic substances. Based on these findings and the higher color permeability of newspaper, printing paper was the most suitable material for HIEP and newspaper was the least suitable. Additionally, silk may still be used in HIEP in small amounts for the production of art, name cards, and clothing tags.     

Fluorescent standards

A number of fluorescent materials have been examined by various organizations and committees with the aim of selecting a suitable set of samples for working standards of fluorescence. The luminescent reference materials (standards) that will best satisfy the industrial requirements are solids prepared for front-surface illumination. These standards, according to the CIE subcommittee on luminescence, preferably should be thin and turbid to simulate products, which are mostly opaque. Since such standards will be used in an industrial environment, they should be rugged, reusable, and very stable to laboratory light and atmosphere. Stability is the most important quality; absolute calibration is not required for industrial use. The needs for the colorimetric and photometric applications of luminescent reference materials appear to be best satisfied by materials used in the front-surface mode and having, as an additional requirement, a measurable diffuse reflectance. This article describes the requirements which should be met, gives the reasons why these standards of fluorescence are needed and by whom, and describes the optical materials considered by various organizations such as the CIE and ISCC.     

Concept of correlated color temperature

The concept of color temperature has been used for many years to characterize the relative spectral distribution of energy from light sources. Since not all sources of light are blackbody radiators, the term “correlated color temperature” was devised to indicate the temperature of the blackbody with chromaticity nearest that of the source. Since the CIE has recently recommended two additional color spaces superseding the existing universally agreed system, it is important to know what effect the new recommendation will have on the correlated color temperature determination. In view of this, it has seemed appropriate to design and carry out some fundamental studies in acceptable color matching among color-normal observers. The isotemperature lines derived from the experimental data described here are within one standard deviation of the isotemperature lines derived from the 1960 UCS diagram. Hence, there is no need to revise the isotemperature lines derived formerly.     

Diffuse reflectance‐factor measurements of rose petals

The diffuse reflectance factor for different colored rose petals is measured as a function of wavelength using a high resolution optical spectrometer. The tristimulus values, the CIE chromaticity coordinates, the dominant wavelength and purity, the CIE whiteness index, the tint index, the CIE 1976 LAB coordinates, as well as CIELAB hue‐angle and chroma are reported. The data on diffuse reflectance factor are presented in the 390?800 nm range at intervals of 10 nm. Using the data, one can generate the perceived color of the roses and the color coordinates in different illuminating light sources and environments. The present data will be useful for the color characterization of flowers, realistic rendering of flowers in computer graphics, color photography, and in the development of filters for color photography. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011     

Colorimetry technique on BaTiO3 and KNbO3 ceramics to determine the phase transition

In this work, colorimetry was used in order to identify the phase transition of BaTiO₃ and KNbO₃ ceramic. The transition of the structure produces a change of color of the ceramic bulks because their optical properties change. The transition phase was detected with a color sensor and reflectance method on ceramic bulks. CIE L*a*b* and CIE L*u*v* color spaces were used to measure the color changes reported. Experimental results showed that the changes of color are suitable for detecting the phase transition in both perovskite structures. The phase transition in the proposed ferroelectric materials was also measured by means of the dielectric constant method and the results obtained were in agreement with the temperatures reported for phase transition changes on BaTiO₃ and KNbO₃. Therefore, the colorimetry technique proposed in this paper proved to be suitable for detecting structure changes as a relationship between color properties and temperature.     

Color rendering of supplementary artificial lighting

Many interiors may be lit by daylight and artificial light; the CIE color rendering index (CRI) of the sources alone is not a characteristic of the complex situation. It is the purpose of this article to derive the general principles leading to the determination of the CRI distribution in such an interior. the CRI is expressed as a function of the proportion α of the combination, for several types of daylight and artificial light. It is shown that the dependence of the CRI on α is linear for supplementary artificial lightings which have the same chromaticity as daylight. Otherwise, nonlinearities are introduced. the time variation of the CRI is also analyzed.     

Did the CIE get it right? A critical test of the CIE color domains for signal lights

Since 1951, the Commission Internationale de L'Eclairage (CIE) has provided influential guidance on the choice of the most suitable colors for colored signal lights. In 1994, the CIE reviewed its 1975 recommendations for signal colors and has recently revised them. These revised recommendations have now been published as a CIE standard. This article reports an experiment designed to test those recommendations and to provide data on the reliability of signal color recognition under a range of conditions. Thirty young subjects (aged 18–28 years) and thirty older subjects (aged 50–64 years) named the colors of lights, the colors of which were located on or close to the color boundaries defined by the CIE for red, yellow, white, green, and blue colors. The angular diameter of the light was one min of arc. In a second experiment, half the subjects named the colors of the lights when the angular diameter was 5 min of arc. Observations were made under both dark and light adaptation. Red signals, especially those located in the CIE Class A domain, were reliably recognized under all conditions. Yellow near the red boundary of the CIE yellow domain tended to be confused with red, especially under dark adapted conditions at low signal illuminances. White was not a reliable signal color and was often confused with yellow, except for a white located near the blue boundary of CIE white. Green colors located near the blue boundary of the CIE color domain for green were less reliably recognized than those of longer dominant wavelength. Blue signal colors located within the CIE Class A blue domain were more reliable than expected, except at very low signal illuminances. There were significant differences in the performance of older compared to younger subjects, some of which can be explained by color shifts occurring as the result of the yellowing of the lens of the eye with age. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 109–122, 2001     

Analysis of the spectral reflectance and color of mineral pigments affected by their particle size

The color of mineral pigments changes obviously with their particle size. However, how the particle size of these mineral pigments affects the color of the mineral pigment color block remains unclear. Based on optical principles and the physical properties of mineral pigment particles, our analysis found that changes in the particle size not only nonlinearly affect the behavior of light at the first surface of the mineral pigment color block, but also affect the interaction of light with the particles within the body of the mineral pigment color block, ultimately changing the spectral reflectance and color of the mineral pigment color block. Finally, we derived a nonlinear monotonically decreasing relationship between the particle size and the spectral reflectance. The experiment conducted in this article selected six kinds of mineral pigments as color block samples and observed the changes in the spectral reflectance and color value with the particle size. These studies are beneficial for color researchers conducting scientific research related to mineral pigments.     

Correlated color temperature as an explicit function of chromaticity coordinates

A simple equation to compute correlated color temperature (CCT) from CIE 1931 chromaticity coordinates x and y is given. Over the range of interest in color science, the errors are negligible. It was derived from the fact that the isotemperature lines for CCTs of principle interest nearly converge toward a point on the chromaticity diagram and the assumption that CCT may be represented by a third-order polynomial function of the reciprocal of the slope of the line from that point to the chromaticity of the light. the equation is useful in designing sources to simulate CIE colorimetric illuminants.     

Color scales in simulated daylight

The pigmentation plan used for production of the color cards made available by the Optical Society of America (OSA) for its Committee on Uniform Color Scales (UCS) was designed in such a manner that the color scales should, within the production tolerances, appear uniform in all phases of daylight. The production specifications were based on D₆₅ of the Commission International de L'Eclairage (CIE) and the CIE supplementary observer (1964) for 10° visual-field subtense. To test for the intended invariance of uniformity of the scales in daylight, for normal observers, the effects on color differences between all nearest neighbors of the OSA colors have been studied for CIE Illuminant C with the 1931 observer, and for a “daylight” fluorescent luminaire (color temperature 6500 K) with both the 1931 and 1964 CIE observers. Although the colorimetric specifications (Y, x, y) of each color card are different for those three illuminant + observer combinations, the color differences computed with the formula of the OSA-UCS committee are, within the production tolerances, unchanged. The purpose of this article is to show how well the aim and expectation is fulfilled—that the uniformity of color differences between nearest neighbors in the scales of the OSA-UCS colors be essentially unchanged for normal observers and for ordinary variations of the quality of natural and artificial daylight. This invariance is found, even for daylight-quality fluorescent-lamp light.     

CIELAB color space boundaries under theoretical spectra and 99 test color samples

A color space is a three-dimensional representation of all the possible color percepts. The CIE 1976 L*a*b* is one of the most widely used object color spaces. In CIELAB, lightness L* is limited between 0 and 100, while a* and b* coordinates have no fixed boundaries. The outer boundaries of CIELAB have been previously calculated using theoretical object spectral reflectance functions and the CIE 1931 and 1964 observers under the CIE standard illuminants D50 and D65. However, natural and manufactured objects reflect light smoothly as opposed to theoretical spectral reflectance functions. Here, data generated from a linear optimization method are analyzed to re-evaluate the outer boundaries of the CIELAB. The color appearance of 99 test color samples under theoretical test spectra has been calculated in the CIELAB using CIE 1931 standard observer. The lightness L* boundary ranged between 6 and 97, redness-greenness a* boundary ranged between −199 and 270, and yellowness-blueness b* boundary ranged between −74 and 161. The boundary in the direction of positive b* (yellowness) was close to the previous findings. While the positive a* (redness) boundary exceeded previously known limits, the negative a* (greenness) and b* (blueness) boundaries were lower than the previously calculated CIELAB boundaries. The boundaries found here are dependent on the color samples used here and the spectral shape of the test light sources. Irregular spectral shapes and more saturated color samples can result in extended boundaries at the expense of computational time and power.     

Chromatographic and colorimetric characterizations of brominated indigoid dyeings

The major indigoids constituting modern and archaeological purple pigments produced from molluskan species include, in varying compositions, indigo, 6-bromoindigo, and 6,6′-dibromoindigo. Though woolen Tyrian Purple dyeings produced from these pigments were the most prized and precious of all dyeings in antiquity, a full chromatographic and colorimetric analysis of multi-fibered textiles dyed with these indigoids has not been previously performed. This current study reports on high-performance liquid chromatographic (HPLC) analyses conducted on the indigoid pigments and on woolen dyeings individually produced from them. In addition, comparative colorimetric analyses via reflectance spectrophotometry were performed on standard multifiber fabric swatches, each consisting of 13 different synthetic and natural fibrous materials. Each swatch was dyed with one of the cited indigoids. These colorimetric properties included the Kubelka-Munk spectral curves, color strengths at the wavelengths of maximum absorptions, color coordinates of the CIE L*a*b* and L*C*h* color spaces, and the color differences. Excellent functional correlations were observed among these properties and these relationships should be applicable to similar dyeings on other fabric materials. The results show that filament triacetate and nylon-66 possess the most remarkable color strengths of all the fiber materials investigated in all the dyeings, and of the natural fibers studied, wool possessed the highest color strength and cotton the poorest with all three dyes. Such chromatographic and colorimetric analyses would further our understanding of the colors produced from ancient, and modern, purple-dyed textiles.     

Deriving instrumental tolerances from pass-fail and colorimetric data

Equations such as CIE94 and CMC are now in common use to set instrumental tolerances for industrial color control. A visual experiment was performed to generate a data set to be used in evaluating typical industrial practices. Twenty-two observers performed a pass-fail color tolerance experiment for a single high-chroma yellow color. Thirty-two glossy samples varying in all three CIE-LAB dimensions were compared with a single standard. A near-neutral anchor pair was used to define the quality of match criterion. The pooled pass data were used to fit a 95% confidence ellipsoid. The chromaticness dimension was well estimated by either CMC or CIE94. The lightness dimension was poorly estimated by either equation. Evaluating the sampling distribution of the 32 test samples via a covariance matrix revealed a poor sampling, particularly in the ΔL*Δb* plane. This sampling may have biased the visual experiment. The visual data were used to optimize various color-difference equations based on CIE94 and CMC, where the l:c and total color difference were adjustable parameters. Several methods of optimization are described including minimizing the number of instrumental wrong decisions and logistic multiple-linear regression. Some methods require only pass response data, while others require both pass and fail data. Because industrial tolerances are usually based on a single observer, ellipsoids were fitted for three observers to demonstrate the large variability between observers in judging color differences. It was concluded that when tolerances need to be set based on a single observer's visual responses of samples not well distributed about the standard, typical industrial occurences, one should only adjust the tolerance magnitude based on a statistically valid equation such as CIE94. One should not change l:c or derive a new ellipsoid. © 1996 John Wiley & Sons, Inc.