Chromatic Variables Research Articles

Visual and Instrumental Color Match Evaluation of Single Shade Composites before and after Bleaching Procedures: A Pilot Study

Background: One of the major challenges in restorative dentistry is to obtain an adequate color match between composite restorations and the surrounding tooth. This match depends on several chromatic variables related to the composite itself but also to the teeth. Bleaching procedures are not to be able to modify the shade of composite restorations to a lighter color as it does on natural teeth. Objective: The objective of this study is to evaluate the visual and instrumental color match of two single-shade resin-based composites in human-extracted teeth before and after bleaching treatment. Methods: Six extracted human posterior sound teeth were used. Round-shaped V-class cavities (2x2x4mm) were prepared buccally 2mm away from the CEJ. Two single-shade resin composites (OM-Omnichroma and VE-Venus Diamond One) were used for the restorations. Tooth color was measured using an intraoral spectrophotometer. Visual analysis was carried out by 16 calibrated observers, and the differences were graded from 0 (excellent match) to 4 (huge mismatch). Teeth were then bleached using 40% H 2O2 (Opalescence Boost PF, Ultradent), and visual and instrumental evaluations were performed after 24 hours. Results: Before bleaching, visual analysis showed a mean value of 0.16 for OM and 0.24 for VE. After bleaching, the color match showed a mean value of 0.14 for OM and 0.22 for VE. Regarding the instrumental analysis, each restoration matched the tooth VITA scale grade before bleaching and followed the natural tooth VITA scale grade after bleaching procedures. Conclusion: Within the limits of this pilot study, both composites seem to have excellent color-match properties with the surrounding tooth structure.

In search for flavonoid and colorimetric varietal markers of Vitis vinifera L. cv Rufete wines

The better adaptation of autochthonous grape varieties to environmental changes is increasing the interest on them. Previous studies on Vitis vinifera L. cv Rufete, the flagship of DOP “Sierra de Salamanca”, demonstrated its phenolic potential to produce quality wines. The present study aims at discovering flavonoid (HPLC-DAD-MSn) and colorimetric (CIELAB) varietal markers in commercial Rufete wines (RW) that could be employed to discriminate them from those made with other varieties or mixtures. Compared to Tempranillo wines (TW), RW showed lower phenolic contents, with lower proportions of anthocyanins and flavonols but greater of flavanols. Principal Component Analysis applied to flavonoid and chromatic variables allowed varietal separation of the samples along PC2, which was mostly driven by %total prodelphinidins, %oligomeric procyanidins and Cab* (greater in TW) and by %monomeric procyanindins and L* (greater in RW) and, additionally, by the proportions of A-type vitisins, acetaldehyde-related pigments, quercetin 3-O-glucuronide and Quercetin/Myricetin ratio (all greater in RW). The results of the present study show that the typicity of Rufete grapes is quite preserved in the wines made with up to 95% of Rufete and 5% of Tempranillo grapes or wines and independently of the enological practices of the different wineries.

Sand-Dust Image Enhancement Using Chromatic Variance Consistency and Gamma Correction-Based Dehazing.

In sand-dust environments, the low quality of images captured outdoors adversely affects many remote-based image processing and computer vision systems, because of severe color casts, low contrast, and poor visibility of sand-dust images. In such cases, conventional color correction methods do not guarantee appropriate performance in outdoor computer vision applications. In this paper, we present a novel color correction and dehazing algorithm for sand-dust image enhancement. First, we propose an effective color correction method that preserves the consistency of the chromatic variances and maintains the coincidence of the chromatic means. Next, a transmission map for image dehazing is estimated using the gamma correction for the enhancement of color-corrected sand-dust images. Finally, a cross-correlation-based chromatic histogram shift algorithm is proposed to reduce the reddish artifacts in the enhanced images. We performed extensive experiments for various sand-dust images and compared the performance of the proposed method to that of several existing state-of-the-art enhancement methods. The simulation results indicated that the proposed enhancement scheme outperforms the existing approaches in terms of both subjective and objective qualities.

Systematic segmentation method based on PCA of image hue features for white blood cell counting.

Leukocyte (white blood cell, WBC) count is an essential factor that physicians use to diagnose infections and provide adequate treatment. Currently, WBC count is determined manually or semi-automatically, which often leads to miscounting. In this paper, we propose an automated method that uses a bioinspired segmentation mimicking the human perception of color. It is based on the claim that a person can locate WBCs in a blood smear image via the high chromatic contrast. First, by applying principal component analysis over RGB, HSV, and L*a*b* spaces, with specific combinations, pixels of leukocytes present high chromatic variance; this results in increased contrast with the average hue of the other blood smear elements. Second, chromaticity is processed as a feature, without separating hue components; this is different to most of the current automation that perform mathematical operations between hue components in an intuitive way. As a result of this systematic method, WBC recognition is computationally efficient, overlapping WBCs are separated, and the final count is more precise. In experiments with the ALL-IDB benchmark, the performance of the proposed segmentation was assessed by comparing the WBC from the processed images with the ground truth. Compared with previous methods, the proposed method achieved similar results in sensitivity and precision and approximately 0.2% higher specificity and 0.3% higher accuracy for pixel classification in the segmentation stage; as well, the counting results are similar to previous works.

Efficient nucleus segmentation of white blood cells mimicking the human perception of color

AbstractIn this study, we present a nucleus segmentation proposal of white blood cells (WBCs) using chromatic features. It is human inspired on perception of color: a person locates the nucleus of the WBCs by the chromatic contrast between the nucleus and the other elements of the blood smear. To implement that, we segment the nucleus by selecting the pixels with high chromatic variance. First, an unsupervised neural network, which was trained offline to recognize different colors is applied to the images. Thereby, the hue of the pixels is normalized, and the chromatic variance is accurately computed. Processing the hue and using the unsupervised neural network the brightness and staining variations are robustly estimated. In previous related works, the color components are processed separately as uncorrelated intensity channels, and the mathematical operations are selected intuitively. Unlike that, we use color as a feature without separating the hue components, keeping their correlation, so the formal treat becomes systematic. Experiments use the RGB and HSV spaces with three public image databases: ALL‐IDB2, CellaVision, and JTSC. A pixel‐level segmentation evaluation is performed by comparing the segmented images with the ground truth. Our proposal competes with current methods since the values in accuracy, specificity, precision, sensitivity, dice coefficient, kappa index, and true positive rate all are similar to or improved upon the state of the art. The performance of our approach is classified as excellent regarding the kappa index value, and it detects at least 80% of the cells with an average dice coefficient larger than 0.9.

Comparison of translucency and opalescence among different dental monolithic ceramics

Statement of problemMonolithic ceramic restorations designed by computer-aided design and computer-aided manufacturing are increasingly being used by clinicians. With the introduction of new materials, their optical characteristics also need to be investigated. PurposeThe purpose of this in vitro study was to compare the translucency and opalescence of lithium disilicate, zirconia-reinforced lithium silicate, presintered zirconia-reinforced lithium silicate, polymer-infiltrated ceramic-network material, and multilayer zirconia. Material and methodsA total of 50 rectangular plates (14×12×1 mm) of 5 monolithic ceramics were prepared in this in vitro study (n=10). Each zirconia specimen was divided into 3 groups of incisal, middle, and gingival thirds. Each group was then evaluated separately. The color parameters of specimens were measured on 3 backgrounds, white, black, and #3 Ivoclar Natural Die Color material, by using a spectrophotometer. The translucency and opalescence of the specimens were determined by the relevant equations, and between-group comparisons were made. One-way ANOVA and Tamhane post hoc tests were used to compare groups (α=.05). ResultsThe difference among the groups was significant in translucency (F=137.346, df=6, P<.001), contrast ratio (F=134.148, df=6, P<.001), and opalescence parameters (F=128.028, df=6, P<.001). The 3 zirconia groups (10.87 ±0.54 to 11.88 ±0.26) had a significantly lower translucency than the other groups, and the zirconia-reinforced lithium silicate group (18.14 ±0.74) showed the highest translucency. Zirconia-reinforced lithium silicate (12.36 ±0.42) had the highest opalescence, and the lowest opalescence was found for polymer-infiltrated ceramic-network (5.43 ±0.28) and the incisal third of zirconia (5.45 ±1.06). ConclusionsThe zirconia-reinforced lithium silicate and presintered zirconia-reinforced lithium silicate specimens had the highest translucency and opalescence. The studied multilayer zirconia, which had different cubic phase values from incisal to gingival blank, showed similar translucency over the entire range, and differences among different regions were related to chromatic variables.

Color variance and achromatic settings.

The average color in a scene is a potentially important cue to the illuminant and thus for color constancy, but it remains unknown how well and in what ways observers can estimate the mean chromaticity. We examined this by measuring the variability in "achromatic" settings for stimuli composed of different distributions of colors with varying contrast ranges along the luminance, SvsLM, and LvsM cardinal axes. Observers adjusted the mean chromaticity of the palette to set the average to gray. Variability in the settings increased as chromatic contrast or (to a lesser extent) luminance contrast increased. Signals along the cardinal axes are relatively independent in many detection and discrimination tasks, but showed strong interference in the white estimates. This "cross-masking" and the effects of chromatic variance in general may occur because observers cannot explicitly perceive or represent the mean of a set of qualitatively different hues (e.g., that red and green hues average to gray), and thus may infer the mean only indirectly (e.g., from the relative saturation of different hues).

Lizard colour plasticity tracks background seasonal changes.

ABSTRACTEnvironmental heterogeneity on a spatial and temporal scale fosters an organism's capacity to plastically alter coloration. Predation risk might favour the evolution of phenotypic plasticity in colour patterns, as individuals who change colour throughout the year may be able to improve their fitness. Here we explored the change in dorsal pigmentation of the Italian wall lizard (Podarcis siculus campestris) at three time points (March, July, October) during a period of activity in a Mediterranean natural area in southern Italy. Following a preliminary investigation conducted in 2018, during 2019 we captured 135 lizards and took a picture of their ventral scales to check for possible recapture over the sessions. Lizard dorsal pictures were collected in the field with the support of a reference chart to quantitatively estimate chromatic variables (hue, saturation and value). At the same time, pictures of the environmental background were collected. Our findings suggest that lizards are capable of altering dorsal coloration during seasonal change. They vary from green at the onset of spring, to brownish in the middle of summer and to a greyish colour in October. This modification closely followed environmental background colour variation and enhanced lizard crypsis during each season.

Optical Detection of Green Emission for Non-Uniformity Film in Flat Panel Displays

Among colours, the green colour has the most sensitivity in human vision so that green colour defects on displays can be effortlessly perceived by a photopic eye with the most intensity in the wavelength 555 nm of the spectrum. With the market moving forward to high resolution, displays can have resolutions of 10 million pixels. Therefore, the method of detecting the appearance of the panel using ultra-high resolutions in TFT-LCD is important. The machine vision associated with transmission chromaticity spectrometer that quantises the defects are explored, such as blackening and whitening. The result shows the significant phenomena to recognize the non-uniformity of film-related chromatic variation. In contrast, the quantitative assessment illustrates that the just noticeable difference (JND) of chromaticity CIE xyY at 0.001 is the measuring sensitivity for the chromatic variables (x, y), whereas JND is a perceptible threshold for a colour difference metric. Moreover, an optical device associated with a 198Hg discharge lamp calibrates the spectrometer accuracy.

The chromatic variance matrix in digital image based methods for the potential evaluation as quantitative procedures

The dispersion matrix or chromatic variance of digital images was proposed to characterize the color amplitude and hence the potential sensitivity of Digital Image Colorimetric determinations. The study provided a generalizable model that quantitatively explained the influence of the analyte and instrumental factors in the color measurements. RGB reflected colors of the yellow-orange complex formed by Hydrogen Peroxide with Ti(IV) were captured by a compact digital camera in an experimental dynamic range. In this context, the dispersion Covariance-Variance matrix of the color information provided the amplitude of the chromatic system. Subsequently Analysis of Variance and Multivariate Statistical demonstrated that 87% of the chromatic variance could be justified by the Hydrogen Peroxide concentration influence, while the camera, as an instrumental effect, and the preparation method, accounted for the 10% and 3%, respectively. Also, the behavior of alternative chromatic variables has been compared. Hydrogen Peroxide presented a ready and efficient digital determination in the range 1–40mgL−1. Statistical comparison with standard procedures demonstrated the absence of systematic errors.

Intemperismo Artificial em Lâminas de Tectona grandis Tratadas com Produtos de Acabamento

RESUMO Este estudo teve por objetivo avaliar a ação do tempo de exposição ao intemperismo artificial na cor de lâminas de madeiras de teca tratadas com produtos de acabamento. Amostras que receberam 2 tipos de produto, a seladora e o stain, mais as testemunhas, sem acabamento. O experimento foi instalado no delineamento inteiramente casualizado, com 3 tratamentos e 4 repetições. As lâminas ficaram expostas ao simulador QUV-Acelerated Weathering Teste, por 7 períodos, de: 6, 12, 24, 48, 96, 192 e 384 horas. Após cada período de intemperismo foram feitas medições das cores, com espectrofotômetro COLOR EYe XTH. As variáveis cromáticas avaliadas foram: L*, a*, b*, C e h*. Ao final do estudo pôde-se concluir que as lâminas de madeira de teca sofreram alterações em sua cor com o passar do tempo de exposição e que o stain apresentou maior eficiência na conservação da cor da madeira.

Early constraints in sexual dimorphism: survival benefits of feminized phenotypes.

Sexual dimorphism (SD) has evolved in response to selection pressures that differ between sexes. Since such pressures change across an individual's life, SD may vary within age classes. Yet, little is known about how selection on early phenotypes may drive the final SD observed in adults. In many dimorphic species, juveniles resemble adult females rather than adult males, meaning that out of the selective pressures established by sexual selection feminized phenotypes may be adaptive. If true, fitness benefits of early female-like phenotypes may constrain the expression of male phenotypes in adulthood. Using the common kestrel Falco tinnunculus as a study model, we evaluated the fitness advantages of expressing more feminized phenotypes at youth. Although more similar to adult females than to adult males, common kestrel fledglings are still sexually dimorphic in size and coloration. Integrating morphological and chromatic variables, we analysed the phenotypic divergence between sexes as a measure of how much each individual looks like the sex to which it belongs (phenotypic sexual resemblance, PSR). We then tested the fitness benefits associated with PSR by means of the probability of recruitment in the population. We found a significant interaction between PSR and sex, showing that in both sexes more feminized phenotypes recruited more into the population than less feminized phenotypes. Moreover, males showed lower PSR than females and a higher proportion of incorrect sex classifications. These findings suggest that the mechanisms in males devoted to resembling female phenotypes in youth, due to a trend to increase fitness through more feminized phenotypes, may provide a mechanism to constrain the SD in adulthood.

Characterization of Thermochromic Fibers’ Response to Temperature Change

The property of some materials to change their color in response to temperature changes is called thermochromism. A polymer fiber manufactured in such way that a thermochromic pigment is embedded in the polymeric matrix material develops accordingly thermochromic functionality and can be used as a temperature change indicator. The characterization of a polymer thermochromic fiber with respect to its color change in response to temperature change is presented in this paper. A specially developed characterization apparatus was developed for this purpose. The temperature span of the involved experiment was from 23.5°C (room temperature) to 60°C, while the tested fiber was found to be responsive regarding its chromatic variance mainly within the temperature range 30.5oC - 50oC. During the involved digital image processing, the chromatic shift of the sample was characterized according to the HSV (hue-saturation-value) color model. Fiber’s original color was found to change with temperature by presenting a monotonic reduction of saturation and value with temperature increase.

The role of chromatic variance in modulating color appearance.

Chromatictarget patches embedded in a chromatically variegated surround appear less saturated than when they are embedded in an achromatic uniform surround (Brown & MacLeod, 1997), which can be construed as either a form of gamut expansion for targets on uniform surrounds or as a form of gamut compression for targets on variegated surrounds.Ekroll, Faul, and Niederée (2004) suggested that the difference in perceived chromaticity on the two surrounds is caused by a layered scene decomposition, wherein the increased saturation of targets on homogenous surrounds is attributed to a decomposition of a target patch into a chromatically saturated transparent layer overlying an achromatic background.Here, we report asymmetric matching data that show the perceived chromaticity difference observed on the two surrounds depends on the particular direction of chromatic variation applied to the variegated surround. If the chromatic variegated surround has the same or a similar hue to that of the target and the saturation variation of the surround is large compared to the saturation of the target the gamut expansion effect is also large. However, if the variegated surround has a different hue than the hue of the target, the perceived chromaticity difference is small and largely does not depend on the variation in saturation of the surround. These results suggest that a layered scene representation cannot fully explain the gamut expansion effect and suggest that a chromatically tuned contrast gain control mechanism may contribute to the difference in perceived color of targets on achromatic homogeneous surrounds and chromatically variegated surrounds.

Effects of stress by unfamiliar sounds on carcass and meat traits in bulls from three continental beef cattle breeds at different ageing times

One-hundred-and-twenty-four young bulls of three Continental beef cattle breeds were used to study the effect of pre-slaughter stress by unfamiliar sounds on carcass traits and quality characteristics of beef aged for three different periods. Stress due to unfamiliar noises had a moderately negative effect on carcass and meat quality. Carcasses from group Stressed had higher (P<0.05) values of pH0, pH24, a*, and Warner-Bratzler shear force, and lower (P<0.05) values of L*, b* and pressure losses than from Unstressed animals. There were significant differences (P<0.05) among breeds in L*, a* and pressure losses. The ageing time had a significant effect on chromatic variables, WBSF and pressure losses. The cooking losses were not significantly affected by any of the three factors discussed. These results emphasize the importance of implementing appropriate management practices during pre-slaughter handling of cattle in order to reduce any possible risk factor for stress, as well as the different sensitivity of the breeds to similar stimuli.

Statistical relationships between soil colour and soil attributes in semiarid areas

Soil colour has become one of the most innovative indicators used to adjust amendment and fertilizer rates in precision agriculture. This paper uses a combination of colour variables together with geographical, management and pedologic variables in order to find relationships between the three colour components (lightness, hue, and chroma) and several soil characteristics, in a semiarid environment. In these areas soils are weakly developed, and organic matter, nitrogen, phosphorous and iron soil contents are usually low and undergo high spatial variability. Multivariate analysis was used to find statistical relationships that: determine soil colour in those environmental areas; reveal the most appropriate chromatic variables for each case; and determine the interactions between variables that can mask the effects of individual variables. Colour measurements were collected with a trichromatic colorimeter . Eighteen soil variables were used, of which eight resulted in statistically significant correlations with colour components. Those variables were sand (%), clay (%), parent material (marls), soil organic carbon (SOC), carbonate content , total nitrogen (TN), iron, and 1:5 soil:water extract electrical conductivity (EC 1:5 ). Only sand was significant for all three colour components. The content of organic carbon was not significant in multiple regression analysis with respect to soil lightness in this study of semiarid soils . However it was significant in bivariate regression, in the same way as found in other studies. • Carbonates, EC, texture, iron and SOC are the most significant variables. • Low levels of chromogen elements do not complicate statistical correlations. • Specific soil variables are significantly correlated with lightness, chroma and hue.

满足夜视兼容显示应用的三基色LED背光配色方法

There are two independent chromatic variables while matching the color of LED backlight based on three primary colors.Night vision radiant luminance and the departure from the color coordinates of certain reference point are two restrictions,under which there exists one and only best color matching scheme.By means of two variables linear regression analysis,approximate relations between radiance and color coordinates are given.Through trial and error procedure from least three rounds of radiant luminance measurement,the best configuration of color can be calculated.According to the analysis of mean residual,the error of estimated radiation can be less than 2% in basic accuracy of measurements and proper range of sampling points.

Reduction of wine 4-ethylphenol concentration using lyophilised yeast as a bioadsorbent: influence on anthocyanin content and chromatic variables

The present work reports the capacity of lyophilised Saccharomyces cerevisiae G37 and Schizosaccharomyces pombe 936 to adsorb 4-ethylphenol, a compound with a negative impact on the sensorial profile of wine. Using SPME-GC/MS, a strong correlation was detected between the quantity of yeast added and the reduction of the initial wine 4-ethylphenol concentration. The adsorption kinetics for each yeast was determined. The impact of this treatment on wine anthocyanin concentration and chromatic properties was investigated by UV–Vis and HPLC–PDAD/ESI–MS analysis. Large reductions in the anthocyanin concentration were detected when effective 4-ethylphenol-reducing quantities of lyophilised yeast were used.

Relative importance of sources of chromatic refractive error in the human eye

The relative importance of the various optical elements of the human eye are analyzed to determine which contribute most to the chromatic variance in total refractive power of the eye. The concept of differential dispersion, defined as the change in the difference in index of refraction across a refractive surface with change in wavelength, is used to provide a theoretical tool for this analysis. The theoretical treatment shows that almost all the chromatic effect will be caused by the air-tear interface. Calculations of model eyes are made that support this view. Four model eyes are examined, an emmetropic eye, a hyperopic eye, a myopic eye, and an emmetropic eye accommodating 2.5 D.

Von Kries versus color constancy

We derive the conditions for which the illuminant-independent behavior of von Kries quotients is good. They are in qualitative agreement with those obtained in the experiment. The key concepts are as follows: narrow sensitivities, their approximation by a δ-function at an appropriate wavelength, and the nature of the reflectance and spectral distribution functions for which the δ-function approximation is good. Color constancy theory aims to construct strictly or almost illuminant-independent perceptual, achromatic and chromatic variables from illuminant-dependent tristimulus values. Deficiencies due to ignoring metamerism and, in constructions, the constraints that spectral distribution functions are nonnegative and reflectance functions assume values between 0 and 1, are identified and corrected, if remediable. Variables are constructed with a more favorable illuminant-independent behavior than von Kries quotients. Helmholtz's (conjectured) interpretation of color constancy is proved to be correct. If color and lightness are illuminant-independent functions of these variables, equality of appearance under test and reference sources occurs if (and under weak conditions only if) they possess the same values under these sources. The resulting chromatic adaptation transform specifies an earlier open proposal (Color Science. New York: Wiley; 1982. 434 p). We prove a result concerning the role of color in discrimination. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010