Small Color Differences Research Articles

A method for selecting training samples based on camera response

In the process of spectral reflectance reconstruction, sample selection plays an important role in the accuracy of the constructed model and in reconstruction effects. In this paper, a method for training sample selection based on camera response is proposed. It has been proved that the camera response value has a close correlation with the spectral reflectance. Consequently, in this paper we adopt the technique of drawing a sphere in camera response value space to select the training samples which have a higher correlation with the test samples. In addition, the Wiener estimation method is used to reconstruct the spectral reflectance. Finally, we find that the method of sample selection based on camera response value has the smallest color difference and root mean square error after reconstruction compared to the method using the full set of Munsell color charts, the Mohammadi training sample selection method, and the stratified sampling method. Moreover, the goodness of fit coefficient of this method is also the highest among the four sample selection methods. Taking all the factors mentioned above into consideration, the method of training sample selection based on camera response value enhances the reconstruction accuracy from both the colorimetric and spectral perspectives.

Application of a colorimetric technique in quality control for printed pediatric orodispersible drug delivery systems containing propranolol hydrochloride

The feasibility of a colorimetric technique was investigated in CIELAB color space as an analytical quality control method for content uniformity of printed orodispersible pediatric delivery systems. Inkjet printing was utilized to fabricate orodispersibe film formulations containing propranolol hydrochloride in a colored ink base using three different edible substrates. A thin sweetener coating layer of saccharin was successfully included in the final dosage forms for palatability purposes using a casting knife. Optical microscopy, scanning electron microscopy and scanning white light interferometry analyses were conducted to study the effect of printing on the surface morphology and topography of the substrates. Differential scanning calorimetry and attenuated total reflectance infrared spectroscopy were used to study the solid state properties and possible interactions between the drug and the excipients. The inkjet printing technique deposited precise and uniform escalating doses (0.08⿿3.16mg) of the active pharmaceutical ingredient onto the substrates (R2⿥0.9934). A disintegration test with clear end-point detection confirmed that all the substrates meet the requirements of the Ph. Eur. to disintegrate within 180s. The colorimetric technique proved to be a reliable method to distinguish the small color differences between formulations containing an escalating dose of propranolol hydrochloride.

The Effects of Analogous Food Color on Perceived Flavor: A Factorial Investigation

ABSTRACTWe extend research testing the effects of food color on flavor perception to analogous color. Analogous colors are those found next to each other on the color wheel. Subjects were assigned the task of tasting and evaluating a fruit-flavored beverage. Actual fruit flavor at two levels and beverage color at three levels were manipulated in a full factorial, between-subjects design. Thus each subject tasted and evaluated a single color/flavor combination. Results show that the small differences in food color represented by analogous color are sufficiently distinct and meaningful to consumers to significantly affect their ability to correctly identify the flavor of color-associated foods, as well as to form distinct flavor profiles and particular preferences—much as the grosser distinctions represented by complementary food color have been shown to do previously.

The colour stability of natural dye coating films consisting of chlorophyll after exposed to UV-A

Purpose This paper aims to study the colour stability of chlorophyll and the effect of copper (II) nitrate – Cu(NO3)2 – as an additive in natural dye coating films after being exposed to ultraviolet-A (UV-A). Design/methodology/approach The natural dye was extracted from the leaves of Cassia alata L. using absolute ethanol as the solvent. The extract was divided into two parts and, one of it was added with 3 wt.% Cu(NO3)2 as an additive. The polymer blend of poly(methyl methacrylate) (PMMA) and acrylic polyol was used as the coating binder. Both parts of the dye with and without additive were mixed with the blended polymer in a specific ratio. The resulted mixtures were applied as coating films on glass substrates. The colour stability of the coating films on exposure to UV-A with the time of exposure was observed with Commission internationale de l’éclairage (CIE) L*a*b* colour coordinates. The hidden power by the means of reflectivity and glossiness of the coatings was also studied. Statistical standard deviation (STD) was used to analyse the data. Findings The test showed that the coating films containing Cu(NO3)2 had smaller colour differences, (ΔE*) indicating higher colour stability. The analysis on hidden power also showed that the coating film with Cu(NO3)2 was 1.6 times more stable than the film without additive. All the measurements in this study were observed within 35 days of duration. Research limitations/implications This paper implies the potential of using natural dye extracted from Cassia alata L. leaves as a stable dye colourant for coating applications. Practical implications The coating film developed in this study is suitable for glass substrate applications. Originality/value A new method of preparing solvent-based coating film from PMMA–acrylic polyol with chlorophyll colourant is introduced in this study.

Influence of Color Education and Training on Shade Matching Skills.

To evaluate the influence of education and training on quality of tooth color matching. Dental students (N = 174), matched the color of eight shade tabs in a viewing booth, using VITA Linearguide 3D-Master shade guide. The experimental group had color education and training between the before and after session. The control group did not have any additional information in between two sessions. Color differences between the task tabs and selected tabs were calculated using CIE formulas. The score for the best match (smallest color difference) was 10 points, the 2nd best match 9 points, down to 1 point for the 10th best match. Means and standard deviations were calculated. Differences were analyzed using the Student t-test. Shade matching scores in the experimental group were significantly better after education and training (p < 0.001), with a mean score before and after shade matching sessions of 7.06 (1.19) and 8.43 (0.92), respectively. The percentage of students in the experimental group that selected one of three best matches increased 24.3%. The control group exhibited no significant improvement in the after session. Within the limitations of the study, education and training improved students' shade matching skills. While the vast majority of dental restorations and practically all restorations in the esthetic zone are tooth colored, the profession as a whole is far from perfect when it comes to accurate shade matching. Education and training can improve shade matching ability: enhanced esthetics of dental restorations, increased patient satisfaction, and a reduced number of color corrections are some of the notable benefits and rewards. (J Esthet Restor Dent 00:000-000, 2016) J Esthet Restor Dent 28:287-294, 2016).

Color Range and Color Distribution of Healthy Human Gingiva: a Prospective Clinical Study.

The aim of this study is to compile a comprehensive database on color range and color distribution of healthy human gingiva by age, gender and ethnicity. Spectral reflection of keratinized gingiva at upper central incisors was measured by spectroradiometer and converted into CIELAB values. Lightness range (ΔL*) for all groups together was 26.8. Corresponding a* (green-red) and b* (blue-yellow) ranges (Δa* and Δb*) were 18.3 and 13.0. Significant differences (p < 0.05) were recorded by age for L* and a* coordinates, by gender for b* coordinate, and by ethnicity for L*, a* and b* coordinates. R2-values between color coordinates were 0.01 (L*/a*), 0.03 (L*/b*), and 0.12 (a*/b*). The smallest color differences were recorded between age groups 46–60 and 60 + (ΔE* = 0.9), and between Caucasians and Hispanics (ΔE* = 1.1). Color difference by gender was 1.3. When total L*a*b* ranges were divided into four equal segments, 51.7% of subjects had L* value within the third segment (from lightest to darkest), 47.1% had a* value within the third segment (from less red to redder), and 59.3% had b* value within the second segment (from less yellow to yellower). It was found that ethnicity and age had statistically significant influence on the color of human gingiva.

Divided spatial attention and feature-mixing errors.

Spatial attention is thought to play a critical role in feature binding. However, often multiple objects or locations are of interest in our environment, and we need to shift or split attention between them. Recent evidence has demonstrated that shifting and splitting spatial attention results in different types of feature-binding errors. In particular, when two locations are simultaneously sharing attentional resources, subjects are susceptible to feature-mixing errors; that is, they tend to report a color that is a subtle blend of the target color and the color at the other attended location. The present study was designed to test whether these feature-mixing errors are influenced by target-distractor similarity. Subjects were cued to split attention across two different spatial locations, and were subsequently presented with an array of colored stimuli, followed by a postcue indicating which color to report. Target-distractor similarity was manipulated by varying the distance in color space between the two attended stimuli. Probabilistic modeling in all cases revealed shifts in the response distribution consistent with feature-mixing errors; however, the patterns differed considerably across target-distractor color distances. With large differences in color, the findings replicated the mixing result, but with small color differences, repulsion was instead observed, with the reported target color shifted away from the other attended color.

THE POTENTIAL OF SPECULAR REFLECTIONS FOR FAÇADE IMAGE ANALYSIS

Abstract. Several approaches for window detection have been proposed in recent years, which all use the window size, shape or position within the façade as characteristics for the detection. In this paper another property of windows is proposed for their detection: Windows are made of glass, so they tend to specularly reflect sun light, while the surrounding wall diffusely reflects it. To this end, colour values in multiple views are analysed to detect specular reflections. In the experiments, walls often show a high homogeneity of small colour differences, and many windows are clearly visible in the form of colour differences. Nevertheless, it is difficult to segment windows from the façade if there is no prior knowledge about the intensity of the scene’s illumination. Promising results are obtained if the façade lies in the shadow, e.g., of another building or a tree.

Microbial Inactivation and Physicochemical Properties of Ultrasound Processed Pomegranate Juice

The effects of ultrasound treatment at various amplitudes (50, 75, and 100%) and times (0, 6, 12, 18, 24, and 30 min) on Escherichia coli ATCC 25922 (a surrogate for E. coli O157:H7) and Saccharomyces cerevisiae ATCC 2366 levels and physicochemical characteristics (monomeric anthocyanins, color values, total phenolics, pH, and soluble solids) were determined in pomegranate juice. More than a 5-log inactivation of E. coli ATCC 25922 and a 1.36-log inactivation of S. cerevisiae ATCC 2366 were achieved after 30 min of ultrasound treatment at 100% amplitude. The log-linear and Weibull models were successfully used to estimate the microbial inactivation as a function of ultrasound treatment time (R(2) > 0.97). No significant changes were observed in total phenolics, pH, and soluble solids of the treated juice (P > 0.05). The ultrasound treatment for up to 30 min resulted in more than 92 and 89% anthocyanin retention at 75 and 100% amplitude, respectively. The redness (a*) of the juice did not change significantly after the ultrasound treatment at amplitudes of 75 and 100% for up to 24 and 12 min, respectively. No significant changes in L* and b* values were observed after ultrasound treatment at all amplitudes and after up to 30 min of treatment for 50 and 75% amplitudes. Small differences in juice color were noted based on total color difference scores.

Color Difference Evaluation for Digital Pictorial Images Using the Magnitude Estimation Method

A new set of color difference data using complex images was collected including small and large color differences. Using 13 images, 182 test images were generated to have various average lightness, chroma or hue values compared to the original images. Twenty observers estimated the overall color difference between the reference and manipulated images shown on an sRGB monitor with 250&#xA0;cd/m2 as a peak white in a dark room. The magnitude estimation technique was adopted for the visual assessment. The parametric factors of CMC(l:c), and CIEDE2000(l:c) were optimized using the color difference data set. Results showed that CIEDE2000 performs better than CMC. The best ratio for CMC(l:c) is (4:3), while (3.5:1) is the best for CIEDE2000(l:c) for overall color difference prediction.

Introducing WLab—Going from Wpt (Waypoint) to a uniform material color equivalency space

AbstractA set of invertible non‐linear transforms was derived that adjusts Wpt (Waypoint) coordinates (based on Wpt normalization) to and from a perceptually more uniform coordinate system (WLab or Waypoint‐Lab) than that provided by Wpt that allows for the advantageous features of Wpt to be directly applied to situations where other standard color spaces are typically used. The proposed transformations were found by optimizing for perceptual uniformity over both large and small color difference scales. The Munsell color order system was used as a representation for optimizing large‐scale perceptual uniformity. Correlations with Munsell value, chroma and hue along with comparisons with CIELAB and CAM02‐UCS were used to correct and assess overall large‐scale uniformity. The ΔE*94 color difference formula was used for optimization purposes for small‐scale uniformity. A STRESS analysis was applied to compare color differences based on Euclidean WLab distances with color differences based upon ΔE*ab, ΔE*94, ΔE00, DIN99o, CIECAM02, and CAM02‐UCS. It was found that WLab is a reasonably uniform material color equivalency space with small Euclidean WLab distances not being statistically different from ΔE*94, ΔE00, and Euclidean distances of DIN99o and CAM02‐UCS under reference observing conditions. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 550–563, 2015

Hα Emission From Active Equal-Mass, Wide M Dwarf Binaries11This publication is partially based on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium.

We identify a sample of near-equal mass wide binary M dwarf systems from the SLoWPoKES catalog of common proper-motion binaries and obtain follow-up observations of their chromospheric activity as measured by the Hα emission line. We present optical spectra for both components of 48 candidate M dwarf binaries, confirming their mid-M spectral types. Of those 48 coeval pairs, we find eight with Hα emission from both components, three with weak emission in one component and no emission in the other, and 37 with two inactive components. We find that of the 11 pairs with at least one active component, only three follow the net trend of decreasing activity strength (LHα/Lbol) with later spectral type. The difference in quiescent activity strength between the A and B components is larger than what would be expected based on the small differences in color (mass). For five binaries with two active components, we present 47 hr of time-resolved spectroscopy, observed on the ARC 3.5-m over 12 different nights. For four of the five pairs, the slightly redder (B) component exhibits a higher level of Hα emission during the majority of the observations and the redder objects are the only components to flare. The full range of Hα emission observed on these variable mid-M dwarfs is comparable to the scatter in Hα emission found in single-epoch surveys of mid-M dwarfs, indicating that variability could be a major factor in the spread of observed activity strengths. We also find that variability is independent of both activity strength and spectral type.

A Similarity Measure for Large Color Differences

Hundreds of large color differences, of magnitude 20 &#x394;E00, were generated and used in a visual sorting experiment. The process of generating these color differences and two specific experiments are described in detail. The results show that small color difference metrics, such as &#x394;E00, do not consistently model the visually sorted differences for large differences. A new similarity measure, based on a cosine similarity between categorical vectors of colors, is described and used to more consistently model large color differences. This similarity metric can be used to better characterize large color errors during reproduction, for image processing operations such as segmentation or as a feature for content retrieval. The new measure can also be applied to visual phenomena, such as categorical perception, in which within category color differences are perceived as smaller than across category differences.

Effects of Instant Pressure Drop Puffing with Super‐Heated Vapor on the Physical Properties of Granny Smith Apple Chips

AbstractA central composite rotatable design of three factors was used to optimize instant pressure drop puffing with super‐heated vapor (IPDPSV) for Granny Smith apple slices. The physical properties of the chips processed by hot‐air drying after IPDPSV, hot‐air drying or freeze drying were analyzed and compared. The results revealed that moisture content, puffing temperature and heating time had significant effects on puffing ratio and color differences. The optimum conditions were 23% moisture content for pre‐dried samples, 122C puffing temperature and 41 s heating time. In these conditions, the puffed slices had a large puffing ratio of 45.137% and a relative small color differences of 4.642. Compared with the chips processed by hot‐air drying or freeze drying, chips processed by hot‐air drying after IPDPSV were brighter in color and had porous structures and suitable hardness. Therefore, IPDPSV is an effective method to improve chips quality.Practical ApplicationsInstant pressure drop puffing with super‐heated vapor (IPDPSV) could increase the pore volume in Granny Smith apple tissue. The effects of puffing parameters, including moisture content in sample, puffing temperature and heating time, on puffing ratio and color difference were studied. On optimized conditions, Granny Smith apple could be effectively puffed with less color change. IPDPSV combined with hot‐air drying gave the best physical qualities for Granny Smith apple chips, such as color and hardness, compared with traditional hot‐air drying and freeze drying. This processing method spent shorter time than hot‐air drying and consumed less energy than freeze drying. We may reasonably infer that IPDPSV has the advantages of productivity and economy. IPDPSV will be a helpful technology to produce high‐quality Granny Smith apple chips.

An optical model relating (L*a*b*) values for a scattering surface covered with a scattering layer to (L*a*b*) values for the uncovered surface and its application to tooth colour

AbstractThe appearance of human dentition is important both psychologically and commercially. Many people perceive the lightness and chromaticity of their teeth as key factors in their overall appearance leading to large businesses in materials for colour‐matched fillings and crowns and in tooth whitening products. The human eye is very sensitive to small colour differences, recognizing a row of highly colour‐matched crowns as unnatural yet seeing excessive colour variation or darkness as unattractive. One cause of tooth discolouration is a darkening of the dentine, visible through the enamel. This has lead the authors to develop a model capable of relating ( ) measurements on a scattering surface, in our case dentine, to ( ) measurements when overlaid by a translucent scattering layer, in our case tooth enamel. The model can be used when any scattering layer is superimposed on a coloured surface. In contrast to existing models, no spectral measurements are necessary allowing the use of colourimeters rather than spectrophotometers. However, there are limitations on the degree of colour saturation for both the coloured surface and the scattering layer as the model uses an approximation valid only for weakly saturated colours. As neither the enamel nor the dentine have strongly saturated colouration, the limitation is entirely acceptable for our work. The use of ( ) measurements directly rather than having to measure the spectrum of reflected light is of practical importance as such measurements in a dental surgery are impossible in all but exceptional cases whilst ( ) measurements in the surgery are routine. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 504–517, 2015

Is the Mediterranean nudibranchCratena peregrina(Gmelin, 1791) present on the Brazilian coast? Integrative species delimitation and description ofCratena minorn. sp.

One of the main difficulties in the taxonomy of heterobranch sea slugs is the interpretation of small morphological and body colour differences in a group of specimens, sympatric or allopatric, as variation of a single species or indicative of similar, but different, species. The aeolid Cratena peregrina is one of the most common and typical nudibranchs from the Mediterranean Sea and was recently informally recorded from Senegal, South Africa, India and in the western Atlantic. In the present work, we investigate the potential presence of C. peregrina on the coast of Brazil. Brazilian and Mediterranean specimens are compared through multiple approaches, including (1) a molecular phylogenetic analysis based on a mitochondrial and a nuclear marker (cytochrome c oxidase subunit I and H3, respectively); (2) performing population analyses such as haplotype networks via TCS and Birky’s coalescence-based K/u ratio; (3) automatic barcode gap discovery and (4) comparative morphological study. As a result of our integrative species delimitation approach, we conclude that the morphological and body colour differences observed between Mediterranean and Brazilian specimens are not due to intraspecific variation in C. peregrina and that C. peregrina is not present in Brazil. Instead, Brazilian specimens belong to a new species, C. minor n. sp., which is described herein. We use this case study to discuss currently available methods of species delimitation and their integrative application to heterobranch sea slugs.

Nonenzymatic Browning Criteria to Sea Buckthorn Juice during Thermal Processing

Nonenzymatic browning reaction is responsible for color and quality changes of fruit juices during thermal processing, and reasonable criteria are crucially important for establishing good manufacturing practice. The nonenzymatic browning criteria of thermally treated sea buckthorn juice from 90 to 120C, i.e., the absorbance at 420 nm (A420nm) and color difference (ΔE*), were investigated. The values of L*, a*, b* and the content of ascorbic acid of sea buckthorn juice during thermal treatment could be fitted to first-order kinetics, while the formation of 5-hydroxymethylfurfural (5-HMF) followed a zero-order kinetics. The changes of ΔE* and A420nm could be estimated by integrated models. The thermal processing parameters for sea buckthorn juice were optimized using kinetic models with low level of 5-HMF and high content of ascorbic acid, and it was found that the thermal processing should be performed at 110C for 0.585 min. Estimation of the activation energy showed that A420nm could be a reasonable indicator for evaluating the nonenzymatic browning of thermally processed sea buckthorn juice from 90 to 110C and ΔE* could be a valuable index at 120C. Practical Applications For fruit juice (puree) processing, optimal parameters are critically important to manufacture products with high quality. During thermal processing, vitamin C degradation, 5-hydroxymethylfurfural accumulation and nonenzymatic browning occur simultaneously. The high quality includes the high vitamin content, the favorable appearance, the smallest color difference between raw material and final product, etc. This article discussed color changes of sea buckthorn juice, a superfruit juice specialized in high vitamin C content and low pH value, during thermal sterilization. Absorbance at 420 nm (A420nm) and color differences (ΔE*), two indicators in controlling nonenzymatic browning during juice processing, were evaluated with kinetic models and used to optimize the thermal processing. Furthermore, the activation energy calculation of A420nm and ΔE* revealed the reasonable criteria on juice quality controlling. All the quality control criteria in this paper showed a guideline of quality control in practical juice manufacturing.

Instrumental Color Evaluation of Ceramic Materials by Using Two Dental Spectrophotometers

Objectives: The aim of the present study was to evaluate the precision of two dental spectrophotometers in evaluating the color parameters of ceramic materials and to assess the accuracy of a dental spectrophotometer (Shade Pilot, Degudent) for analyzing color parameters of lithium-disilicate ceramic materials. Methods: The CIE L*a*b* color parameters, chroma and hue angle of 6 groups of lithium-disilicate ceramic ingots were recorded: MO0, HO0, LTA1, HTA1, LTBL1, HTBL. The measurements were performed in a viewing-booth under a D65 illuminant. Statistical analysis was performed to assess the precision and differences between the two color-measuring devices. Results: Significant differences were found between all color parameters recorded (p&lt;0.001). The difference varied depending on the type of ceramic ingot assessed. The HO0 ingot showed the highest color difference (ΔE=19.18), while the smallest color difference was found for the MO0 ingot (ΔE=5.62). Conclusions: Color parameters of ceramic materials can be recorded with both color-measuring devices, the VEA showing the highest precision.

Performance of select color-difference formulas in the blue region.

The main objective of this work was to test the performance of major formulas for assessment of small suprathreshold color differences in the blue region. The models examined include CIELAB color space based equations, including CIELAB, CIE94, CIEDE2000, CMC (l:c), BFD (l:c), and formulas based on more uniform color spaces, such as DIN99d, CAM02-SCD, CAM02-UCS, OSA-GP, and OSA-Eu in comparison against data obtained via visual assessments. For this purpose, a dataset around the CIE high-chroma blue color center, hereafter called NCSU-B2, was developed. The NCSU-B2 dataset comprised 65 textile substrates and a standard, with a mean ΔE(ab)* color difference of 2.72, ranging from 0.54-5.72. Samples were visually assessed by 26 subjects against the reference gray scale in three separate trials with at least 24 h between assessments. A total of 5070 assessments were obtained. The standardized residual sum of squares (STRESS) index was used to examine the performance of various formulas for this dataset, as well as a previously developed NCSU-B1 low-chroma blue dataset [Color Res. Appl. 36, 27, 2011], and blue centers from other established visual datasets. Results show that formulas based on more recent uniform color spaces provide better agreement with perceptual data compared with models based on CIELAB space.

Color difference formulae evaluation by method of adjustment

This experiment was carried out to test color difference formulae by method of adjustment. 6 different color centers (Red, Yellow, Green, Blue-Green, Blue and Violet) were chosen for this psychophysical experiment. 336 virtual sample pairs were prepared. The mean color difference was three CIELAB units. Each pair was assessed by a panel of 15 observers using psychophysical methods called Method of Adjustment. These visual data were used to test color-difference formulae: CIELAB, CMC, CIE94, DIN99d and CIE2000 with the help of simple statistical measures i.e., PF/3 and Stress. It was found that the visual results obtained from psychophysical method of adjustment show that CIE94 as well as DIN99d still perform well for small color differences.