Metamerism Index Research Articles

Optimal design of colour formulation prediction for cotton fabrics based on NSGA‐II and TOPSIS

AbstractThe prediction of colour formulation is an important step in reproducing the target colour. At present, there are relatively few researches on multi‐objective colour formulation problem, and the colour matching accuracy needs to be improved. In this research, a multi‐objective evolutionary meta‐heuristic method based on the Fast and Elitist Multi‐objective Genetic Algorithm (NSGA‐II) was proposed to predict the target colour recipes. The method used dye concentration as a variable and included three objective functions: (1) minimising the CMC (Colour Measurement Committee) colour difference between the formulation colour and the target colour, (2) minimising the metamerism index, and (3) minimising the cost of the formulation. The algorithm could obtain the Pareto optimal solution set after iteration. On this basis, the best combination of formulations was selected from the optimal solution set by combining the Expert Scoring Method (ESM), Entropy Weight Method (EWM) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The prediction effect of the model was evaluated by taking cotton fabrics and reactive dyes actually used in plant as examples. The results showed that 87.5% of the formulations met the CMC colour difference value of no more than 1, the metamerism index of 90.0% of the formulations did not exceed 1, and the cost of 92.5% of the formulations was reduced relative to the maximum extent in the Pareto optimal solution set. Further studies should be focused on removing duplicate individuals to give better diversity in the Pareto optimal solution set.

Matching target color in polyolefins by estimating pigment concentrations using a four-flux model.

In applications of computer color formulation where color stimuli are optically thick (e.g.,textiles, coatings, etc.), a simple single-constant or two-constant theory (e.g.,Kubelka-Munk model) would suffice. To accurately predict reflectance and transmittance of materials with optical thickness ranging from optically thin to optically thick (e.g.,plastics), mathematically complex radiative transfer theories (e.g.,many-flux models) have been recommended. A many-flux model can even predict color formulation involving special-effect pigments (e.g.,metallic, pearlescent, etc.), but implementation of such models is manyfold complicated. In the current study, applicability of a relatively simple Maheu-Letoulouzan-Gouesbet (MLG) four-flux radiative transfer model to optically varying pigmented polyolefins is thoroughly investigated. First, the MLG model was implemented to determine absorption and scattering coefficients of over 120 pigments where a new mean relative absolute spectral error (MRASE) between measured and calculated spectral reflectance and transmittance of the calibration samples was minimized as an objective function. Second, currently determined absorption and scattering coefficients were further validated by color recipe prediction of 350 historical product colors. Measured and predicted reflectance curves were compared in units of MRASE, CIEDE2000 color difference, metamerism index, root mean square error, and goodness-of-fit coefficient. Moreover, transmission matching was evaluated in units of percent difference between the required and predicted average transmittance. Results showed that with the current implementation of the MLG four-flux model, color recipes of at least 95% of the target colors can be predicted within the acceptability thresholds in units of different error metrics used in the study.

Illuminant metamerism between natural teeth and zirconia restorations evaluated with a chromatic adaptation transform

Little is known about the effect of illuminant metamerism between natural teeth and zirconia restorations, despite their increasing clinical popularity. The purpose of this in vitro study was to compare illuminant metamerism between pairs of natural teeth and layered zirconia restorations and pairs of natural teeth and monolithic zirconia restorations under 10 different illuminants and analyze their metameric potential. Spectral reflectance factors were obtained from 10 pairs of extracted natural teeth and layered zirconia restorations and 28 pairs of extracted natural teeth and monolithic multilayer zirconia restorations. Each pair showed a color match that was within the visual threshold for clinical acceptability (CIEDE2000≤1.8). A special index of metamerism for the change of illuminant (Milm) was calculated from the CIEDE2000 color difference equation. Descriptive statistics and the one-sample t test were used to analyze the results for the Milm and for both groups of layered and monolithic zirconia restorations (α=.05). Layered zirconia restorations reached a mean ±standard deviation value for Milm=0.3 ±0.2 and Milm=0.5 ±0.4 for monolithic zirconia restorations (P<.01). The effect of illuminant metamerism between natural teeth and zirconia crowns was weak and generally within the clinical acceptability limit.

Optical‐physical and inkjet printing properties of created hybrid CaCO3 coated papers

AbstractThe aim of this study is to examine the role of different formulations of calcium carbonates on the inkjet printing quality, with the use of cationic carboxymethyl cellulose (CMC)‐starch as a binder in the formation of the coating structure of paper to use for inkjet printing. For this, GCC (ground calcium carbonate), PCC (precipitated calcium carbonate) and ECC (eggshell calcium carbonate), which have been tried as new coating materials in recent years, are mixed in different proportions to form a different coated formulation and plastered on the newly produced paper surface. Then, optical and physical tests of the obtained samples are carried out. Then, printing properties of the papers on which drop‐on‐demand system inkjet printing is made are examined. According to the obtained data, it is determined that the optical properties of coated paper with GCC + PCC blends outperformed papers coated with other blends. According to the physical test results, GCC + PCC blended coated papers showed the best performance in breaking length and tear indices. ECC + PCC blended coated papers however showed the best performance in burst indices. It is determined that as the particle size of the calcium carbonates in the coating materials decreased, the burst indices value also decreased. This situation is the opposite for breaking length and tear indices values. When the inkjet printing features are examined, it is seen that the best results are obtained from GCC + ECC coated papers in general. The most optimal metamerism indices results, measured under three different light sources, are obtained on GCC + PCC coated papers.

Color Formulation of Cotton Fabrics Using Multi-Objective Ant Colony Optimization

ABSTRACT The formulation of colors is one of the most important aspects of colorimetry. For dyeing and finishing industries, mastering this step is a major problem to be solved. In this paper, a multi-objective ant colony optimization algorithm is developed to optimize the reproduction of the desired shades. The multi-objective function of the proposed algorithm minimizes simultaneously the CMC color differences and the metamerism index between the standard and the reproduced colors. Two ranges of dyes were used to dye cotton fabrics. The elaborated multi-objective algorithm showed good results with small values of color differences and metamerism index. All CMC color differences values were less or at the limit of the acceptability threshold of 1, and about 75% of samples exhibited minimum metamerism and are considered as a good match.

Quantifying observer metamerism of LED spectra which chromatically mimic natural daylight

When LEDs are used to mimic daylight, a side-by-side comparison of the chromaticity difference between the LED spectrum and natural daylight will be perceived differently by individual observers. The magnitude of this effect depends on the LED light's spectral power distribution and can be assessed by using individual observer functions. To minimize the computational effort, an observer metamerism index can be utilized. Here, we compare three methods from the literature to define an observer metamerism index by carrying out a correlation analysis, in which reference spectra of the whole daylight range (1600 K to 88000 K) are used together with an empirical study. The recommended metric is based on a principal component analysis of 1000 individual observers' color matching functions to define a deviate observer. Using the proposed metamerism index significantly simplifies the calculation of the observer metamerism evaluation. Thus, this metric can be applied in spectral optimization pipelines, which are embedded in smart and adaptive multi-primary LED luminaires.

Compatibility of binary mixture of natural dyes for developing compound shades for cotton khadi fabric

The compatibility rating of any two natural dyes applied together for obtaining compound shade has been determined. The natural dyes selected for compatibility study are, babool (BL), pomegranate rind (PR), madder or manjistha (MJ), red sandal wood (RSW), tesu flower (TF) and catechu (CT) based on their maximum commercial use. The dyes have been extracted in aqueous medium under optimized conditions and their binary mixtures in different proportions are used to dye cotton khadi fabric for developing varying compound shades on 15% overall concentration of myrobolan (harda) and aluminium sulphate (75:25) in sequence double pre-mordanted cotton khadi fabric. After dyeing with binary mixtures of natural dyes , dyed cotton fabric samples are subjected to evaluation of K / S , colour differences (∆E), colour difference index (CDI) values; changes in hue /chroma, brightness index (BI), metamerism index (MI) etc; and also colour fastness to washing, light, rubbing and perspiration. The compatibility of these binary pairs of natural dyes has been assessed conventionally (∆c vs ∆L and K / S vs ∆L), as well as using an unique and simple novel method of compatibility test applied for assessing relative compatibility rating (RCR) of each binary pairs of natural dyes, by evaluating colour difference index [(∆E x ∆H) / (∆C x MI)] for application of different proportion of two dyes in each binary pair. The results of this novel simple method are found mostly in well agreement with the findings of compatibility test by conventional methods. Finally, the order of relative degree of compatibility of these binary pairs of natural dyes is found to be BL: MJ &gt; BL: RSW &gt; BL: CT &gt; BL: PR &gt; BL: TF

Dye Extraction from Immature Wood Apple, Characterization and its Eco-Friendly Application on Cotton, and Silk Fabrics

The application of natural dye has been thriving due to its eco-friendly coloration process on textiles by reducing chemical usage. In this research experiment, immature wood apple has been extracted in three different solvents such as ethanol, methanol, and water. Retention factor by Thin Layer Chromatography (TLC) and dye extraction percent were employed selecting the best solvent for dye extraction from the wood apple. Following then, silk and cotton fabrics had been dyed with that extracted dye in the most appropriate solvent. The wood apple dye had also been characterized by UV-vis absorbance, FTIR analysis, and antimicrobial activity test against two bacteria (E. coli and B. subtilis). Moreover, the dyeing performance of dyed fabrics had been evaluated by color co-ordinate value, dye pick up percentage, color strength, Metamerism Index and various colorfastness properties. It has been observed that wood apple shows better antimicrobial activity when extracted in ethanol in case of both bacterial stains. Whereas, after application on fabrics, silk exhibits a higher color strength value and dye pick-up percent compared to dyed cotton fabrics. The colorfastness properties of dyed silk and cotton are also admirable

Optimization of the light‐emitting diode daylight simulator based on the CIE metamerism index method

AbstractBy using spectral loss simulation, it was found that six spectral bands are needed to produce a daylight simulator with good performance. The optimization model for both Commission Internationale de l'Eclairage metamerism index and luminous efficacy (LE) of light‐emitting diode (LED) daylight simulator (LDS) was developed. The optimal LDSs with AA grade for D50, D55, D65, and D75 illuminants should consist of the violet LEDs with violet phosphor excited by an ultraviolet chip, and the white LEDs with green, yellow, and red phosphors excited by a blue chip. Their limit luminous efficacies under the ideal case could reach 179 to 204 lm/W. And finally, a scheme for a spectrally tunable LDS with AA grade was presented.

A multiprimary lighting system for customized color stimuli

AbstractIn this article, a dual seven‐primary lighting system is constructed for color research and education. The system offers sufficient spectral variability to approximate the spectral power distribution of a variety of standard illuminants. More importantly, the constructed multiprimary lighting system was verified to have crucial advantages over conventional displays/projectors to probe observer metamerism through the generation of individualized metameric color stimuli. An observer metamerism index to describe the potential for observer metamerism of any generated stimulus pairs with respect to the population variation of color‐normal observers is formulated. The metric is further extended for use in quantifying the potential for observer metamerism of any lighting system or a system‐primary combination. Moreover, 10 pairs of lighting stimuli, customized for exhibiting high degrees of observer variability, were produced using the system as a step toward creating a device for the color matching functions characterization of individual observers, a so‐called observer calibrator.

METAMERISM INDEX OF LED LIGHT ON HALFTONE COLOUR IMAGES

Skin face detection in photo imaging, is an important component of systems for detecting similarities in visual perception, tracing faces through illumination and metamerism. This paper presents an evaluation of the skin perception under standardized conditions of varied light sources: cool-white fluorescent “store light”, 6500K fluorescent “daylight”, and incandescent “home light”, Led light 6500 K, 2700K, 4000K CCT. In cases where the discrepancy is large, the resulting index of metamerism can be misleading. A small index of metamerism and a large change of color under illuminant metamerism has a different interpretation than what is perceived. This has been demonstrated through small colour variations in print through CMYK colors. The implication is that particular indices of metameric should only account for a limited range under different light conditions. The method used in this paper is based on visual perception, which aim to work with a wide variety of individuals, under varying lighting conditions under the influence of standard daylight, but in this case we also used the Led light 6500K correlated colour temperature, and variations of skin color tones, comparing the illuminant metamerism of visual perception based on different reflectance power distributions (SPDs).

A CMOS Photodetector for Direct Color Imaging

A novel photodetector for imaging in the visible-near infrared range is investigated. Unlike currently used detectors, the proposed device does not require thin film filters for spectral discrimination. Instead, the discrimination relies on the wavelength-dependent absorption property of semiconductor materials. The detector consists of a window exposing the silicon substrate to the electromagnetic signal. Besides the window, multiple collectors separated by polysilicon gates are laid out. Proper voltage biasing establishes a different spectral response for each collector, thus creating a detection color space. Experimental results demonstrate the color detection capability of a three-collector imaging pixel from sensitivity metamerism index calculations. The sensor is fabricated in a standard 0.35-μm CMOS process and presents a peak combined collectors' responsivity of 0.35 A/W.

Wpt (waypoint) shift manifold difference metrics for evaluation of varying observing‐condition (observer + illuminant) metamerism and color inconstancy

AbstractMetamerism is a critical color phenomenon which can cause serious problems for products assembled by various parts. Customers generally expect all parts are color‐matched under different observing conditions. This article extends the concepts of illuminant and observer metamerism to observing‐condition metamerism, that is, objects are color‐matched under one observing condition but not under others. The color inconstancy of a single object is also expanded to be evaluated under multiple observing conditions. Moreover, four Waypoint (Wpt) Shift Manifold difference metrics are proposed to evaluate not only observing‐condition metamerism of metamers and paramers but also observing‐condition color inconstancy of single objects: The Mean Object Inconstancy Index (MOII), The Mean Object Color Difference (MMOCD), Object Metamer Index (OMI), and Object Hue Similarity Index (OHSI). Existing indices of metamerism and color inconstancy employ appearance matching using a Chromatic Adaptation Transform (CAT) and color difference formulas such as CIEDE76 or CIEDE2000. The proposed metrics utilize material matching based upon the Waypoint Material Adjustment Transform (Wpt‐MAT) and Euclidian color difference in the perceptually uniform Material Color Equivalency Space WLab. Conceptual comparisons between these approaches are discussed and evaluated. Additionally, computational evaluation results under observing conditions composed by 99 illuminants and 70 observers show that MOII provides a measure of color inconstancy for single objects, MMOCD provides a measure of metamerism between metamers and paramers with a generalized assessment of color difference between two objects, OMI provides a measure of paramers, and OHSI provides a quantitative measure of hue characteristics for different observing conditions.

Optimization of a spectrally tunable daylight simulator using four quantum dot light‐emitting diodes for visual appraisal of color

AbstractAn optimization model for luminous efficacy of a spectrally tunable light‐emitting diode (LED) daylight simulator under constraint of metamerism index was developed. It was first reported that the optimal spectrally tunable LED daylight simulator of AA grade for D50, D55, D65, and D75 standard illuminants could consist of two quantum dot‐integrated LEDs (QDLEDs) with the ultraviolet chip and two other QDLEDs with the blue chip. The optimized spectral parameters of each QDLED, as well as photometric and colorimetric performances of D50, D55, D65, and D75 daylight simulators, were obtained by maximizing luminous efficacy under the metamerism index for both a visible and ultraviolet range less than 0.25. The limit luminous efficacies of four daylight simulators using four QDLEDs under the ideal case will reach 181 lm/W to 205 lm/luminous efficacies with a radiant efficiency of both the ultraviolet and blue chips of 60%, as well as a quantum efficiency of a quantum dots layer of 90%, will reach 100 lm/W to 112 lm/W.

Study on metamerism degree evaluation based on wavelength sensitive cone weighting algorithm

AbstractMetamerism phenomenon can be used in illuminant detection to ensure the accuracy of light source. A method based on Long‐, Middle‐, Short‐ wavelength cones(LMS) weighting algorithm to evaluate metamerism degree is proposed. The chromatic relationship between the degree of metamerism mismatch and the light source is studied. Herein, the consistency between the metameric indices (MIs) and CIE1976 L*a*b* color difference ranking is analyzed by SRCC, KRCC, PLCC and RMSE. A statistically sampling method to obtain practical LMS cone fundamentals to evaluate metamerism degree is employed. The analysis results obtained show that the method based on LMS weighting algorithm has good evaluation ability and stability in simulation experiments and statistically sampling experiments, which are in line with visual characteristics of human. Proposed method meets the requirements of selecting metameric pairs used in light source detection. The analysis results have certain guiding significance.

The color metamerism evaluation of paint based on ocean spectrum

The surface color of the sea is affected by many factors and will be different the due to the material difference in the sea. And the difference will be reflected in the ocean spectrum. If the paint materials of a ship can simulate the ocean surface color and the ocean spectrum at the same time. This will minimize the metamerism. In this paper, the method of metamerism is used to evaluate paint based on ocean spectrum, so that the color of the material affected by the light source will be reflected in the metamerism index.

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

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

Metamerism Appreciation of Jadeite‐Jade Green under the Standard Light Sources D65, A and CWF

AbstractWe tested 288 pieces of the polished cabochon jadeite‐jade with high quality green and smooth surfaces using the colorimeter Color i5 based on the CIE 1976 L*a*b* uniform color space. The color changes after alternating three CIE standard light sources D65, A and CWF were compared, and the degree of metamerism was evaluated. The results show that the CIE standard light sources D65, A and CWF increase the chroma of green and turn bluish green into vivid green, which are similar or to nearly colorless and transparent glass‐like samples with fine textures. When the three light sources were individually alternated, the lightness of the jadeite‐jades showed little change, but the tone changed significantly. Metamerism occurred only in 3 pairs among the 16 samples that were selected by cluster analysis for quality, and the metamerism colors were highly consistent of L*D65∊(43.47, 46.75), C*D65∊(65.20, 68.80) and ho*D65∊(138.10, 140.23). We can conclude that the jadeite‐jade green gradually turns to blue when the color temperature of the light source increases. But when considering both the light sources and the samples, D65 is more suitable to be the light source of jadeite‐jade green when compared with the light sources CWF and A. Compared with the CIE standard green and high chroma green, high‐quality jadeite‐jade green has a slight yellow tone, low lightness and high chroma. The special metamerism index decreased to 1 when the light source alternated among D65, A and CWF. Therefore, the color of jadeite‐jade green might be slightly influenced by alternating of the light sources.

Colorimetric Characteristics of Metamerism of Yellowish Green Peridot

Fifty-one yellowish-green color 5mm×7mm oval faceted peridots are experimented by Color i5 to test their color parameters, and concept of metamerism is introduced into this article, to analyze the effects of color parameters on the color appearance of peridots. SPSS analysis indicates: wavelength λ has no correlation with metamerism index MI, but excitation purity Pe has significant correlation with MI (rPe×MI=0.826, 0.01), means with the increase of excitation purity, the color appearance of peridot tend to be more unsteady and change more with the illumination conversion. Simultaneously, metamerism index MI increase with increasing chromaticity C* and lightness L* (rC*×MI=0.979, rL*×MI=0.889, 0.01), means the change of color appearance increase with illumination conversion. In conclusion, when the yellowish-green of peridot is more saturate and brighter, the effect of illumination on color appearance is greater.

Application of image quality metamerism to investigate gold color area in cultural property

A concept of image quality metamerism as an expansion of conventional metamerism defined in color science is introduced, and it is applied to segment similar color areas in a cultural property. The image quality metamerism can unify different image quality attributes based on an index showing the degree of image quality metamerism proposed. As a basic research step, the index is consisted of color and texture information and examined to investigate a cultural property. The property investigated is a pair of folding screen paintings that depict the thriving city of Kyoto designated as a nationally important cultural property in Japan. Gold-colored areas painted by using high granularity colorants compared with other color areas are evaluated based on the image quality metamerism index locally, then the index is visualized as a map showing the possibility of the image quality metamer to the reference pixel set in the same image. This visualization means a segmentation of areas where color is similar but texture is different. The experimental result showed that the proposed method was effective to show areas of gold color areas in the property.