The effect of gloss on color

A model was developed for the effect of gloss on reflected color, taking the measurement geometry of the color measuring device into account. It considers the total front surface reflectance of a given sample to be independent of gloss and determined only by its refractive index and the angle of the incident beam. Although the total front surface reflectance is fixed, its specular component increases (and the diffuse component decreases) with increasing sample gloss. Therefore, the diffuse reflectance factor measured by a spectrophotometer decreases with sample gloss. In this article, a defined curve was fitted to the measured reflectance factor of black xerographic print samples having a range of gloss values for the 0/45 and diffuse spectrophotometer geometries, and this curve was used to predict the CIELAB color values for samples of the other colors at various gloss levels. The predicted color was compared to the measured color for cyan, magenta, yellow, red, green, and blue images that spanned a wide range of gloss. The RMS color error between the predicted and measured color of all of these images was found to be about 3 CIELAB ΔE* units. © 1999 John Wiley & Sons, Inc. Col Res Appl, 24, 369–376, 1999     

Influence of surface roughness on the diffuse to near‐normal viewing reflectance factor of coatings and its consequences on color measurements

In this work, we discuss the effect of surface roughness on the measurement of the diffuse to near‐normal viewing reflectance factor of coatings and evaluate its impact on the corresponding color coordinates. We compare specular component included (SCI) and excluded measurements. We introduce a gloss‐factor to account for surface roughness in specular component excluded measurements. We present experimental results on samples with different degrees of surface roughness. Samples in this study were chosen to expose the contribution of the surface in the reflectance factor. For slightly rough surfaces, the influence on the measured reflectance factor depends on whether the specular‐component is included or excluded. As the surface roughness increases, the specular‐excluded reflectance factor increases approaching its value with the SCI further roughness lead to similar measurement results in both configurations. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 177–187, 2013.     

Evaluating contrast gloss of textured polymeric surfaces

The concept of contrast gloss and its relation to visually perceived gloss was examined for textured polymeric specimens. The specimens were injection‐molded plaques manufactured in three different polymers (acrylonitrile‐butadiene‐styrene copolymer, polypropylene, and a blend of polycarbonate and acrylonitrile‐butadiene‐styrene copolymer). A contrast gloss factor was determined from the reflectance data obtained with a conventional multiangle spectrophotometer. To evaluate the visual impression of gloss of the specimens a psychometric study was performed. The contrast gloss factor corresponded well with the visual assessment of the gloss and it was able to discern the visual differences between several specimens not significantly discriminated by their gloss values. These latter gloss values were obtained with a conventional glossmeter measuring specular gloss. In correspondence with the visual assessments and practical experience, the relation between the contrast gloss factor and the specular glossmeter measurements was found to depend on the type of polymer used. When evaluating gloss of specimens varying in color, the contrast gloss factor corresponded well with the visual assessments. This was in contrast to the specular glossmeter measurements which ranked the specimens essentially in the opposite order. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Optical reflectance measurement of large-scale graphene layers synthesized on nickel thin film by carbon segregation

The change of surface roughness during graphene synthesis on evaporated Ni thin films was monitored. It was found that Ni is highly agglomerated during high temperature annealing but the surface roughness is made smoother by the coverage of graphene. It is demonstrated that diffuse reflectance is a fast and convenient technique for evaluating surface roughness over a large area of graphene on a metal film, and specular reflectance is a good indicator of the coverage of graphene on the metal film.     

Effect of texture on color variation in inkjet‐printed woven textiles

Inkjet‐printed textiles are influenced by a wide range of parameters due to highly diverse textile structures and the resulting textures. The goal of this study is to understand the effect of texture on color appearance in inkjet‐printed woven textiles. Cotton‐woven samples were constructed with nine different weave structures. Each sample was digitally printed with identical squares of primary colors cyan, magenta, and yellow and secondary colors red, green, and blue. The amount of ink applied was controlled consistently with an image editing software. CIE L* values were calculated from the measured reflectance. 25 observers ranked the perceived texture and color lightness of each sample. Perceived visual texture and perceived color lightness scales were estimated from the rankings using the rank order method. The measured CIE L* values and the scale of perceived lightness were positively related for the primary and secondary colors. Instrumental measurements of the textile surface characteristics were positively related to the visual scale. Texture was demonstrated to cause a measurable effect on color results in inkjet printing, both using instrumental and perceptual measures. To investigate if the color differences were substantial enough to cause “out of tolerance” ratings in textiles based on common textile industry color acceptance procedures, color differences among the samples were calculated and compared to a reference sample. Results demonstrated that color variation due to texture was sufficient to lead to rejection of a printed color in comparison to a color specification. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 297–303, 2015     

Gloss and goniocolorimetry of printed materials

Angular distribution of reflectance spectra and of colorimetric parameters for printed papers (varnished and not) and foils, clear and metallized, were measured by goniospectrophotometry, with a photomultiplier for visible region, or a spectrocolorimeter as a detector, keeping the light source in a fixed position, ?45° anormally. All reflectance spectra were related to near‐Lambertian BaSO₄ powder white standard, relative to which the color coordinates were calculated. The photometric cosine law holds for an ideal diffuser; consequently, all color parameters are significantly perturbed by gloss in a large region, several 10's of degrees around the specular angle. The reflectance peak in the specular angle region of glossy material can be well approximated by the Lorentz function, especially in the vicinity of the specular angle. Lightness, chroma, and hue angle in the gloss angle region suffer as a result of high changes and extremes depending on the gloss of the material tested. This is what complicates color measurements and full determination or definition of the complex appearance of printed materials. The change of chroma with varnishing of glossless materials was clearly elucidated. It was found that “bottom color gloss” considerably influences the appearance of printed metallized foils or other prints on high glossy substrates. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 335–342, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10177     

Correction of single‐beam sample absorption error in a hemispherical 45°/0° spectrophotometer measurement cavity

A mathematical model for quantifying single‐beam sample absorption error in a hemispherical 45°/0° measurement cavity is derived and tested by measuring diffuse reflectance standards with a prototype visible‐range spectrophotometer. A methodology is described for using this three‐parameter model to correct for sample absorption error in any single‐beam spectrophotometer. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 436–441, 2014     

Reflection of light from semi‐infinite absorbing turbid media. Part 1: Spherical albedo

The purpose of this article is to study the accuracy of a number of simple approximate equations for the spherical albedo r (or the hemispherical reflectance under diffuse illumination conditions) of semi‐infinite light scattering absorbing media, using numerical solutions of the nonlinear integral equation for the reflection function of a semi‐infinite turbid medium, as formulated by V. A. Ambartsumian. We find that the van de Hulst approximation provides the most accurate approximation for the diffuse reflectance r under diffuse illumination conditions. The value of r depends almost exclusively on the value of the similarity parameter , where ω₀ is the single scattering albedo and g is the asymmetry parameter. A simple approach to derive the normalized absorption spectra of particulate matter from reflectance measurements is proposed. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 491–497, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20262     

Toward the soft metrology of surface gloss: A review

The most straightforward way to assess the glossiness of a surface is by measuring the specular reflectance by use of a specular glossmeter. Although alternative measurement methods have been proposed, this is still the most frequently used instrumental measurement technique for gloss evaluation until today. However, due to both the multidimensional nature of gloss perception and to the initial purpose of a specular glossmeter only to judge the gloss differences of surfaces with similar appearance, specular glossmeter results do not seem to provide a reliable basis for estimating the gloss appearance of a surface. During the past decades, increased attention has been paid to understanding how the human visual system arrives at a particular sensation of surface gloss, and which factors influence this process. This article was established in response to these new insights, and provides the reader an overview of the most important developments and findings regarding gloss measurement and gloss perception over the past 15 years. With the ultimate goal to achieve a better correspondence between gloss measurement and gloss perception in the future, issues of alternative measurement methods are considered, and some suggestions for relevant future research are proposed. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 559–570, 2014     

NIST reference goniophotometer for specular gloss measurements

The measurement of specular gloss consists of comparing the luminous reflectance from a test specimen to that from a gloss standard, under the same geometric conditions. The reference goniophotometer described here was designed and characterized to comply with the geometric and spectral conditions specified in the international documentary standards for specular gloss measurements at the standard geometries of 20, 60, and 85°. In addition, this instrument measures the bi-directional luminous reflectance and transmittance for incident angles from 0 to 85°. The goniophotometer and the measurement procedures used to determine the specular gloss of nonmetallic samples are described in this paper, as well as the characterization of the instrument and uncertainty analysis. The minimum relative expanded uncertainty (k=2) for the reference goniophotometer is 0.3%. Optical Technology Div., Gaithersburg, MD 20899-8441.     

Determination of exact absorption behaviour in the mid-infrared spectral range of poly(methylmethacrylate) by Fourier transform infrared reflection spectroscopy

In the present work we demonstrate that infrared absorption fre-quencies and band shapes of poly(methylmethacrylate) (PMMA) homopolymers vary strongly with the type of spectra recorded. The reason is that, in general, any measured optical quantity, such as absorption, transmittance or reflectance, is a complicated function of the refractive index, n(ν), and the absorption index, k(ν), of the material. Kramers–Kronig analysis is applied to external reflection spectra from a single polymer surface measured near the normal incidence angle. Absorption spectra, k(ν), are then deduced and used to calculate grazing angle specular reflectance, attenuated total reflectance, diffuse reflectance and transmission spectra. Then, it is shown that the calculated spectrum for each experiment accurately predicts the experimental one, proving that differences are optical artifacts and not true sample differences. Exact peak absorption for PMMA is 1730cm^-1 and should be taken as a reference value for the calculation of frequency shifts for further physico-chemical interpretation such as specific interactions or molecular orientation. ©1997 SCI     

Infrared hemispherical reflectance of carbon nanotube mats and arrays in the 5–50 μm wavelength region

We present the absolute infrared (5–50 μm) hemispherical reflectance of films produced from commercially available carbon nanotubes. Spectra were obtained with the NPL directional-hemispherical reflectance measurement facility. One group of samples consisted of mats of carbon nanotubes sprayed on copper or silicon substrates. Another group consisted of vertically aligned carbon nanotubes grown on silicon. Two of the materials studied exhibited the lowest hemispherical reflectance so far observed in the infrared wavelength region.     

The BCRA–NPL Ceramic Colour Standards,Series II – Master spectral reflectance and thermochromism data

The master set of the BCRA–NPL Ceramic Colour Standards, Series II, has been calibrated by NPL in the specular excluded, specular included and 0/45 geometries at a temperature of 25C. Tables of spectral reflectance and colorimetric data are presented. The thermochromism of the standards in the specular excluded geometry was also measured by NPL and the changes in spectral reflectance for a 10 degC change in temperature are given. The corresponding changes in colour data for the specular excluded geometry were calculated by NPL. Following a request from the Colour Measurement Committee of the Society of Dyers and Colourists, the corresponding changes in colour data for the specular included geometry were calculated by the Scottish College of Textiles on the assumption that the changes in spectral reflectance are the same for both geometries. Thus changes of colour data are presented for the specular excluded and specular included geometries. It has been shown by Ceram Research that it is possible to use these thermochromism data to correct colour data measured at an arbitrary laboratory temperature to a standard temperature.     

FTIR Spectra of faceted diamonds and diamond simulants

FTIR spectra of faceted diamonds and diamond simulants collected by diffuse reflectance, transflectance, and specular reflection techniques were compared. The transflectance technique exploited total internal reflection phenomenon within the faceted diamond for the spectral acquisition. The transflectance spectra were similar to the well-accepted diffuse reflectance spectra with equal or better spectral qualities. Based on the observed spectral features of the faceted diamond, classification of the diamond, determination of defects, impurities, and treatment process (i.e., irradiation and high pressure and high temperature) can be performed.     

Diffuse reflectance behavior of the printed cotton/nylon blend fabrics treated with zirconium and cerium dioxide and citric acid in near- and short-wave IR radiation spectral ranges

Near- and short-wave IR emission spectra of printed cotton/nylon blend fabrics coated with inorganic compounds in order to tune their diffuse reflectance behavior to the ones with woodland and desert backgrounds are investigated. In this regard, cotton/nylon blend fabrics printed with a four-color digital pattern were used as the substrate, and different concentrations of zirconium and cerium dioxide (ZrO₂ and CeO₂) with and without citric acid as a cross-linker were loaded on these fabrics using the pad-dry-cure method. The diffuse reflectance of the coated fabrics with various concentrations of nanoparticles and a cross-linker was first measured by near-infrared (NIR) diffuse reflectance spectroscopy (DRS). Then, fabrics with an optimum concentration of nanoparticles and appropriate reflectivity profiles similar to woodland and desert were investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), washing, and rubbing fastness properties. In general, NIR and short-wave infrared (SWIR) reflectance of fabrics coated with ZrO₂ and CeO₂ nanoparticles in range of 1% to 1.5% (w/v [%]) was suitable for matching with different environments. According to the findings obtained from the durability test, it was concluded that the washing fastness of the treated fabrics with CeO₂ nanoparticles was excellent in both environments. FE-SEM images of the treated fabrics containing ZrO₂ and CeO₂ indicated that the presence of nanoparticles on the surface of fabrics in woodland patterns was greater than the desert ones. However, the coated fabrics with CeO₂ and citric acid in the woodland pattern have shown better dispersion with a mean particle size of 30 to 60 nm.     

Combined soft lithographic transfer‐printing and patterning method of highly fluorinated polymers as a facile surface treatment protocol

A combined soft lithographic transfer‐printing and patterning method of highly fluorinated polymers was investigated aiming to establish a facile surface treatment protocol for various substrates. Spin‐coated layers of poly(1H,1H,2H,2H‐perfluorodecyl methacrylate) (PFDMA) on patterned polydimethylsiloxane (PDMS) molds were transfer‐printed successfully on silicon, glass, aluminum substrates, resulting in the well‐controlled production of nano to micrometer‐scale periodic structures. With careful optimization of the dimension and density of the PFDMA patterns, it was possible to achieve a water contact angle as high as 175° on the transfer‐printed highly fluorinated polymer film. One of the advantages of the transfer‐patterning method is that highly fluorinated polymer films can be printed on curved surfaces while retaining their superhydrophobic and corrosion‐prevention character. In addition, the transfer‐printed PFDMA layers on the glass plates showed enhanced light transmission, which led to the extraction of 10% more light when they were applied to the emitting side of green organic light‐emitting devices. The micro‐patterned PFDMA surfaces also exhibited a significantly reduced level of bacterial adhesion when they were incubated in human bile juice. These results strongly suggest that the proposed facile transfer‐patterning protocol of highly fluorinated polymer films can be a suitable surface‐treatment technique for implantable electronic devices that exhibit improved device performance and anti‐biofouling nature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45184.     

Quantification and prediction of visually perceived specular gloss at three illumination/viewing geometries

In the present study, attempts were made to clarify the existence of a correlation between visually perceived and instrumentally measured specular gloss of a series of achromatic samples. To this end, seven achromatic physical scales of specular gloss each consisting of 10 or 11 samples were prepared using lithographically printed black, white, and five in between gray papers. The samples were visually assessed and subsequently quantified in terms of a visually uniform color constant lightness scale, by a panel of 14 observers in an especially designed unidirectional light compartment at three illumination/observation geometries, namely 20°/20°, 60°/60°, and 85°/85°. Four statistical parameters were utilized to determine the correlation between visually perceived and instrumentally measured specular gloss. The results show that the instrumental 60°/60° geometry is capable of efficiently quantifying the equivalent specular gloss as perceived by a human observer. Surprisingly, it was also possible to accurately predict the visually quantified specular gloss both at the 20° and the 85° geometries by the aid of applying special linear relationships derived from the instrumentally measured specular gloss of the 60° geometry.     

Transferring the 45/0 spectral reflectance factor scale

The accuracy of spectrophotometric measurements is limited by the standards that are used to calibrate the instrument. Therefore, the procedure used in transferring the spectral reflectance factor scale from one material to another for use in calibration must induce the minimum amount of error. the Munsell Color Science Laboratory has been transferring the spectral reflectance factor scale to calibration materials using a statistical method to correct for the most pervasive systematic errors in the measurement process. This method is based on a statistical procedure in which a set of systematic spectrophotometric errors are estimated based on the measurement of seven NIST primary standards and corrected in subsequent measurements. the optimization of the spectral reflectance factor scale to NIST standards minimizes the induced error. the average reflectance factor error consistently found between the corrected measurements of the NIST standards and their certificate values have been 0.0006 and the average δ_ab has been on the order of 0.2.     

Surface reflectance estimation by the dichromatic model

A method is described for estimating the surface-spectral reflectances of glossy objects when the color signal is a mixture of diffuse reflections, specular reflections, and interreflections. The objects are inhomogeneous dielectric materials, and the reflected light is measured using a spectroradiometer. We first describe the main idea; the color signals, reflected from two closely apposed surfaces with a single interreflection between them, can be expressed by a linear combination of the illuminant spectrum and two diffuse spectral reflection functions. We introduce a representation in which each of these three terms is projected onto a point on a unit sphere. Estimation of the diffuse reflection functions is then reduced to finding the vertices of the spherical triangle. Next, an algorithm is described to estimate the locations of the vertices of diffuse reflectance functions from the measured samples. The reliability of the algorithm is demonstrated in an experiment using two plastic objects with glossy surfaces. © 1996 John Wiley & Sons, Inc.     

Enhancement of the Mie scattering effect using floatstone-like TiO2 spherical micropigment

Floatstone-like TiO₂ microparticles with an efficiently enhanced Mie scattering effect were developed by thermofusing of rutile-type TiO₂ submicron particles on the template core of poly(acrylate) microspheres. The light reflectance of the floatstone-like TiO₂ microparticles was approximately 10% higher than that of the usual rutile-type TiO₂ submicron particles in a wavelength range from 400 to 850 nm. The diffuse reflectance of the microparticles is enhanced by the formation of a floatstone-like structure, whereas there is no difference in the specular reflectance of the particles. As an application of the floatstone-like TiO₂ microparticles, the contribution of the particles to the light-trapping effect of a solar cell was examined. The power conversion efficiency of the solar cell was enhanced by 22% with the introduction of a light-scattering layer composed of the floatstone-like TiO₂ microparticles.