Hue Groups Research Articles

Brightness and hue judgment of dyed hair color

This study aims to investigate human hair color perception through two empirical studies in the context of colored hair. The preliminary study was intended to establish a numerical representation of perceptually meaningful brightness levels. It identified that the brightness level was proportional to the power of 0.766 of L*. In the visual assessment, participants (N = 47) categorized 246 hair color samples into eight color hue groups aligned with the Munsell system. Hue judgment was conducted by visually comparing dyed hair tresses with natural black hair. Based on the L*, a*, and b* values of hair tresses and visual assessments thereof, we observed the ranges of hue categories for hair color alongside the brightness levels. Additionally, the differences between the Munsell hue names and the assessment results were compared. Predominantly influenced by the dark brown hair color, the neutral orientation was shifted to the first quadrant of the a*-b* plane. The study contributes to an understanding of human hair color perception and provides insights into color categorization and labeling, especially when the context is confined.

Three-dimensional representation of the Vita Toothguide 3D-Master: An in vivo clinical study.

The Vita Toothguide 3D-Master (Vita Zahnfabrik) is considered the dental shade guide in which the three dimensions of color - lightness, hue, and chroma - are most well-ordered in the CIELAB color space. No research has yet explored how well the Vita Toothguide 3D-Master is ordered in the 3D color space by recording color coordinates in vivo. To evaluate the spatial color distribution of the Vita Toothguide 3D-Master's lightness, chroma, and hue groups and its 26 physical shade tabs. The dental color (L*, C*, h°, a*, and b* color coordinates) of a healthy maxillary central incisor was recorded for 1361 participants (aged between 18 and 89 years) using a Vita Easyshade Compact spectrophotometer (Vita Zahnfabrik). The R 2.7.2. statistics program was used to create the visual representations. The five lightness levels are those that are best distributed in the color space, in relation to the L* coordinates, followed by the chroma group and, finally, the hue group. The 5M1, 5M2, and 5M3 physical shade tabs are situated at a greater distance apart from the other tabs in the color space. The Vita Toothguide 3D-Master's 26 physical shade tabs are satisfactorily distributed in three-dimensional space, although strict mathematical criteria are not followed. The natural dental shades that fall lower on the lightness scale are the most poorly represented by the physical shade tabs. Darker teeth are poorly represented by the Vita Toothguide 3D-Master's physical shade tabs. The spatial distribution of dental shade guides needs to be improved to ensure they provide homogeneous coverage of the entire chromatic spectrum corresponding to natural teeth. This would help reduce the errors inherent to the subjective visual color selection process.

A Clinical Study Comparing the Maxillary Anterior Tooth Shade and Fabricated Crown Shade of the Western Uttar Pradesh Population to Commercial Shade Guides.

Background It is essential for dentists and technicians to work together to fabricate and create restorations that are a "perfect" shade match for a particular person. Thus, the Vitapan 3D-Master tooth shade system (Vita Zahnfabrik, Germany) was created and put into use in order to improve the accuracy of shade-selection operations. The objective was to visually assess the color of the maxillary anterior teeth in male and female subjects from various age groups in Uttar Pradesh, India. Materials and methods There were 150 patients in total, and they were divided equally into three groups of 50: Group I, which included patients aged 18 to 30; Group II, which included patients aged 31 to 40; and Group III, which included patients aged 41 to 50. Ceiling-mounted fluorescent lighting fixtures with PHILIPS 65 D tubes (OSRAM GmbH, Germany) were installed. Three medical experts provided their opinions as part of this research. The maxillary central incisor was placed next to tabs of various shades, and the doctors' final assessment was based solely on the central one-third of the face. From each of the two sample sets, a total of 30 patients were selected. Once the crown had been made from the prepared tooth of the patient, it was colored according to two shade guidelines (Vita Classic and Vita 3D Master). The three clinicians matched the shade of the manufactured crown with visual shade guides. For shade matching, a modified United States Public Health Service (USPHS) standard was employed. Results The Chi-square test was used to compare categorical variables across groups. According to the Vitapan Classic shade guide, 26% of Group I participants matched the first Hue group (A1), 14% of Group II participants matched the first Hue group (A3), and 20% of Group III participants matched the second Hue group (B2). Master shade guide for Vita 3D 26% of Group I participants matched with the second value group (2M2), 18% of Group II participants matched with the third value group (3L 1.5), and 24.5% of Group III participants matched with the third value group (3M2). Eighty percent of people who were matched to Alpha scored for crowns made using the Vita 3D Master shade guide, while 94.1% of people who were matched to Charlie scored for crowns made using the Vitapan Classic shade guide in a comparison of the two shade guides. Conclusion The majority of the shades obtained from the Vita 3D master shade guide were found to be 1M1 and 2M1 in the younger patients, 2M1 and 2M2 in the second age group, and 3L 1.5, 3M2 in the older age group. In contrast, the Vitapan Classic shade guide revealed A1, A2, A3, B2, C1, D2, and D3 as the predominant shades.

Predicting Munsell color for turfgrass leaves

AbstractLinking turfgrass color to hue, value, chroma (H V/C) in the Munsell Plant Tissue Color Book is a visual comparison process for specifying and communicating plant color. If subjectivity of visual comparison can be mitigated, then the accuracy of color matching may be improved. Research was conducted to develop an algorithm predicting H V/C from CIE‐xyY color (xyY) in digital images of leaves of four turfgrasses. First, value‐chroma (V/C) arrays for Munsell hue groups 5Y, 2.5GY, 5GY, 7.5GY, 10GY, and 2.5G were converted to xyY. Next, chromaticity (xy) plots from each array were fitted with 95% prediction bands. Then, xy points for leaves (N = 60) for each turfgrass were plotted versus prediction bands. The prediction interval containing the most leaf xy points specified leaf H. Pairing each V from each hue group (N = 98) with its corresponding Y regressing log10V on log10Y predicted leaf V from leaf Y (log10V = 0.0715 + 0.5303logY – 0.0332logY2). Pairing each C (N = 98) with its corresponding xy predicted leaf C from leaf xy (C = −11.6021 − 11.2908x + 48.0880y). Predicted H V/C for “Champion” and “TifEagle” hybrid bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon × Cynodon transvaalensis Burtt‐Davy] was 10GY 8/4 and 7.5GY 8/4 mirroring H V/C predicted from xyY using open‐source algorithms in R and Python. The experimental algorithm predicted H V/C accurately, and objectively advancing the way turfgrass color is specified and communicated. Specifying turfgrass color in situ could be possible by interfacing the algorithm with smartphone technology.

The threshold of color inconstancy

Color inconstancy refers to significant changes in the perceived color of an object across two or more different lighting conditions, such as daylight and incandescent light. This research focusses on defining the threshold of color inconstancy between generated D65 and A illumination through a psychophysical experiment. Although modern color appearance models provide equations to calculate the degree of adaptation, a neutral grey match experiment was completed to produce a more accurate D values for the experimental viewing conditions. Like setting an instrumental color tolerance experiment, a second, sorting, experiment was used to define the threshold of color inconstancy. This threshold is the color shift, expressed in color difference terms, required for observers to notice a color change across changes in illumination. In addition, the tolerance ellipsoid for each Munsell principal hue group was also established.

Color Inconstancy of Chromatic and Achromatic Textile Fabrics with Changes in the Correlated Color Temperature and Luminance of the Light Source

This study quantitatively analyzed how the color appearance of textile fabrics of varying lightness, chroma, and hue changes under a broad spectrum of illumination conditions. The color appearances of 203 chromatic (R, YR, Y, GY, G, BG, B, and RB) and achromatic fabrics were measured spectroradiometrically under 16 light sources with different correlated color temperatures (2700, 4000, 5000, and 6500 K) and luminances (50, 100, 500, and 1000 cd/m2). The color appearance values were compared with the spectrophotometrically measured physical color values of the fabrics, which were regarded as their true colors. The differences ranged up to 12.45 ∣ΔL*10∣, 19.32 ∣ΔC*ab,10∣, 161.83∣Δhab, 10∣, and 16.70 ΔECMC(2:1) units, which were significantly higher than the color discrimination thresholds of the human eye. Among 9 hue groups of fabrics, the color appearances of BG (bluish-green) fabrics were generally most affected by light sources, while those of achromatic fabrics were least affected with mean ΔECMC(2:1) of 6.32 and 1.03, respectively. It was also found that the correlated color temperature of light sources significantly affected all the lightness, colorfulness, and hue of fabrics, and the different trends of these effects were observed for different hue groups. Unlike current knowledge, light sources with a correlated color temperature of 6500 K did not always produce color appearances that most closely resemble the actual physical colors. Meanwhile, the luminance of light sources did not have a profound effect on the color appearances of fabrics.

Weighting the Relevance of the Different Colours in Subjective Assessments of Colour Preference

Observers made subjective colour preference judgements about different arrangements of coloured objects in different scenes. While doing so, observers had to assess the importance (so-called weight) of every one of seven colour groups or hue groups (skin tone, red, orange, yellow, green, blue and purple). The scenes were illuminated by high-CRI spectra at four different correlated colour temperatures (CCTs). Red and orange obtained the highest weights (this means that red and orange are the most important colours for subjective colour preference); yellow, green and blue were intermediate while skin tone had only a little weight. CCT had only a small effect while scene content (e.g. “office” vs. “painting”) had a strong influence. Objects of higher chromaticity in the same colour group obtained a higher weight across the different scenes. Latter finding resulted into a predicting formula of the weights.

Color harmony algorithm: an art-inspired metaheuristic for mathematical function optimization

In the last 3 decades, metaheuristic algorithms have received more popularity because of their superior performance to solve large and complex optimization problems. Most of these algorithms are inspired by biological phenomena, social behavior of animals, science and art. Among these four sources, the last one is utilized only by one algorithm. In this paper, we propose another novel art-inspired population-based metaheuristic, called color harmony algorithm (CHA), for solving the global optimization problems. The proposed method models its search behavior through combining harmonic colors based on their relative positions around the hue circle in the Munsell color system and harmonic templates. We utilize simultaneously four different fitness information to construct the hue groups, which improve search ability of the algorithm. CHA has two different phases including the concentration phase and the dispersion phase which are employed to explore and exploit the search space. The performance of the proposed method has been examined using several benchmark test functions commonly used in the literature. To show the effectiveness and robustness of the proposed method, the results are compared with those obtained using ten well-known metaheuristic algorithms. Also, the Wilcoxon Signed-Rank test is conducted to measure the pair-wise statistical performances of the algorithms. The results indicate that besides the simplicity of the proposed algorithm, CHA can outperform the other considered algorithms in terms of the convergence speed and the number of function evaluations.

Study of the most frequent natural tooth colors in the Spanish population using spectrophotometry.

PURPOSETo identify the most frequent natural tooth colors using the Easyshade Compact (Vita -Zahnfabrik) spectrophotometer on a sample of the Spanish population according to the 3D Master System.MATERIALS AND METHODSThe middle third of the facial surface of natural maxillary central incisors was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Caucasian Spanish participants aged between 16 and 89 years. Natural tooth color was recorded using the 3D Master System nomenclature. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3.RESULTSThe results show that the most frequent dental color in the total sample studied is 3M1 (7.05%), followed by the intermediate shade 1M1.5 (6.91%) and 2L1.5 (6.02%).CONCLUSIONAccording to the research methodology used, and taking into account the limitations of this study, it can be proposed that the most frequent color among the Spanish population is 3M1; the most common lightness group is 2; the most frequent hue group according to the 3D Master System is M and the most frequent chroma group is 1.5.

A clinical study relating CIELCH coordinates to the color dimensions of the 3D-Master System in a Spanish population

Statement of problemThe 3D-Master System comprises 26 physical shade tabs and intermediate shades. Determining the relationship among all the groups of lightness, chroma, and hue of the 3D-Master System (Vita Zahnfabrik) and the L*, C*, and h* coordinates is important, because according to the manufacturer, 2 Toothguide 3D-Master shades need to be mixed in a 50:50 ratio to create an intermediate shade. PurposeThe purpose of the study was to relate the lightness, chroma, and hue groups of the 3D-Master System with the polar coordinates of the CIELAB chromatic space, L*, C*, and h*, and to quantify the shades tabs and intermediate shades of the 3D-Master System according to color coordinates. Material and methodsThe middle third of the facial surface of a natural maxillary central incisor was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Spanish participants aged between 16 and 89 years. Natural tooth color was recorded in the 3D-Master nomenclature and in the CIE L*, C*, and h* coordinates system. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. ResultsIn the L* variable, the minimum was found at 47.0 and the maximum at 91.3. In the C* variable, the minimum was found at 5.9 and the maximum at 49.8, while for h*, the minimum was 67.5 degrees and the maximum 112.0 degrees. ConclusionsDespite the limitations of this study, the 3D-Master System was found to be arranged according to L*, C*, and h* coordinates in groups of lightness, chroma, and hue. The corresponding groups of lightness, chroma, and hue can be estimated on the basis of L*, C*, and h* coordinates.

Optimal employment of color attributes to achieve saliency in icon matrix designs

AbstractWith the wide use of smart devices, through which information is presented in vast quantities, objective guidelines are needed to enable designers to choose appropriate colors for information display. The purpose of this study is to determine which colors are the most eye‐catching in displays that employ icon matrices and thereby provide empirical grounds for strengthening the visual information structure of interface designs. Three attributes of color, which include hue, tone, and color combinations, are examined to optimize the color saliency in information displays. An eye‐tracking study was conducted to evaluate saliency objectively by analyzing fixations of visual attention. Based on the hue‐saturation‐brightness color system, a 5‐by‐5 matrix of 25 color patches was adopted to generate 21 color stimuli. Part I of the study focused on hue and indicated that warm colors are perceptually more eye‐catching relative to cool and neutral colors. Part II of the study investigated tonal influences and revealed that highly saturated colors provoked the greatest visual magnetism against a black background across all hue groups, although there was an alternative tendency for a blue hue. Contrary to expectations, no distinctive patterns were observed among brightness groups. With regard to color combination, Part III of the study provided empirical verification that high contrast between a foreground and a background generates a more dominant conspicuity. The results of the present study can be applied in designing electronic interfaces that display icon matrices to create effective communication by guiding visual attention and increasing aesthetic satisfaction. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 429–436, 2015

3D Master Toothguide according to L*, C*, and h* coordinates

ABSTRACTThe purposes of this study are to describe the color coordinates of the 26 shade tabs of the 3D Master Toothguide according to their L*, C*, h* coordinates, and to calculate ΔEab*, ΔL*, ΔC*, and Δh* in the 26 shade tabs. The tooth color of 1361 maxillary central incisors was measured “in vivo” using a spectrophotometer. Tooth color was recorded following the 3D Master system and its corresponding L*, C*, h*color coordinates. Of the 325 shade tabs pairs compared a color difference ( ) of between 2.6 and 5.5 units was found in 9.54% (31 pairs). In 291 pairs (89.54%) there was color difference that exceeded the 5.5 units. Only 0.92% of the color differences () were less than 2.6 units. The minimum color difference ( ) found was 2.1 units and the maximum 45.0 units. The intervals in lightness, chroma, and hue groups between adjacent shade tabs were not uniform. In conclusion, this toothguide is clearly ordered regarding lightness or the L* coordinate. Most of the color differences between the 26 shade tabs of the 3D Master exceed the perceptible threshold of 2.6 units. Some clinical implications are as follows: the 26 shade tabs of the 3D Master Toothguide offer improvements as far as spatial arrangement is concerned. Thus, it is highly possible that the subjective visual color of the measurement would be correct. If there is a mistake when choosing the shade tab from the 3D Master guide there will quite probably be an unacceptable color difference from the clinical point of view. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 518–524, 2015.

Shade Guide Optimization-A Novel Shade Arrangement Principle for both Ceramic and Composite Shade Guides When Identifying Composite Test Objects

The most widely used shade guide for composite materials is made of ceramic and arranged according to a non-proven method. There is a need for a composite shade guide using a scientifically based arrangement principle. To compare the shade tab arrangement of the Vitapan Classical shade guide and an individually made composite shade guide using both the originally proposed arrangement principle and arranged according to ΔE2000 values with hue group division. An individual composite shade guide made from Filtek Supreme XT body colors was compared to the Vitapan Classical shade guide. Twenty-five students matched color samples made from Filtek Supreme XT body colors using the two shade guides arranged after the two proposed principles--four shade guides in total. Age, sequence, gender, time, and number of correct matches were recorded. The proposed visually optimal composite shade guide was both fastest and had the highest number of correct matches. Gender was significantly associated with time used for color sampling but not regarding the number of correct shade matches. A composite shade guide is superior compared to the ceramic Vitapan Classical guide when using composite test objects. A rearrangement of the shade guide according to hue, subdivided according to ΔE2000, significantly reduces the time needed to take a color sample and increases the number of correct shade matches. Total color difference in relation to the lightest tab with hue group division is recommended as a possible and universally applicable mode of tab arrangement in dental color standards. Moreover, a shade guide made of the composite materials itself is to be preferred as both a faster and more accurate method of determining color.

Potential of visible and near-infrared spectroscopy to derive colour groups utilising the Munsell soil colour charts

A study was undertaken to investigate the potential of visible (VIS) and near-infrared (NIR) spectroscopy to derive soil colour groups as a new methodology that might assist in soil type classification. A fibre-optic VIS–NIR spectrophotometer (306.5 – 1710.9 nm) was used to measure the light properties in reflectance mode of 342 dry soil samples collected from fields in Belgium and Northern France. The colour of soil samples was measured with the Munsell soil colour charts, dividing soil samples into two groups of 236 and 106 samples belonging to Hue 2.5Y and Hue 10YR, respectively. Factorial Discriminant Analysis (FDA) was performed separately on each Hue data using the first five Principal Components (PCs) of a Principal Component Analysis (PCA) carried out on colour groups defined a priori. Considering the 2.5Y Hue group, soil samples were classified successfully into four colour groups with a correct classification (CC) of 87.3% and 81.8% for the calibration and validation spectra, respectively. Lower accuracy was observed for the 10YR Hue group for classification into three groups, since 79.6% and 75.0% of samples were correctly classified for calibration and validation sample sets, respectively. Establishing four colour groups by combining both Hue groups decreased the classification accuracy considerably. In order to improve the classification accuracy, the first 5 PCs and first 2 PCs of PCA performed on soil spectra and on the total carbon (Tot-C), extractable phosphorous (Ext-P) and texture index (Ti), respectively, were pooled (concatenated) into a signal matrix and analysed newly by the FDA. This led to improvement of the classification results of four Hue 2.5Y groups (CC of 82.1% and 89.1%) and three Hue 10YR groups (CC of 84.1% and 82.4%). However, best concatenation results of four groups for the combination of both Hue groups were obtained when only Tot-C and Ext-P were considered without Ti, obtaining a CC of 84.2% of the validation data sets. This suggests that the VIS-NIR spectroscopy combined with chemometric tools has the potential of identifying different soil colour groups for a large geographical area.

Shade Matching by Dental Students

Dental students achieved a high identification rate for darker shades (P14 and P24) on the Portrait IPN shade guide, which represent the highest chroma and lowest value in the grayish and reddish yellow hue groups. A high identification rate was also obtained for P32, representing the lowest chroma and highest value in the reddish gray hue group. The data suggest that dental students had the most difficulty determining the correct hue group for unmarked shade tabs. Incorrect responses tended to remain in the same value and chroma range but were selected in a different hue group.

Linear bases for spectral reflectance functions of acrylic paints

A linear model for representing reflectances has been developed from a group of 5574 samples of acrylic paint on paper. Using acrylic paints makes easy the generation of a large variety of samples by mixing, due to the high miscibility among these kinds of pigments: this point was the key to achieve a great spatial homogeneity in our samples. Besides, these kinds of paints keep their chromatic properties stable over time. The first 7 vectors of the so-called overall linear basis were sufficient for a more than adequate mathematical representation of the spectral-reflectance curves. A study by hue groups of the mathematical properties of these curves indicates that the use of a hue basis of representation implies, on the average, a reduction in 1 or 2 of the number of vectors needed in order to achieve results analogous to those of the overall basis. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 39–45, 1998

Linear bases for spectral reflectance functions of acrylic paints

A linear model for representing reflectances has been developed from a group of 5574 samples of acrylic paint on paper. Using acrylic paints makes easy the generation of a large variety of samples by mixing, due to the high miscibility among these kinds of pigments: this point was the key to achieve a great spatial homogeneity in our samples. Besides, these kinds of paints keep their chromatic properties stable over time. The first 7 vectors of the so-called overall linear basis were sufficient for a more than adequate mathematical representation of the spectral-reflectance curves. A study by hue groups of the mathematical properties of these curves indicates that the use of a hue basis of representation implies, on the average, a reduction in 1 or 2 of the number of vectors needed in order to achieve results analogous to those of the overall basis. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 39–45, 1998

Colors Compared: Matisse and Picasso with Chanel and Vionnet

The objective of this research was to test the relationship between the fine arts and couture clothing in respect to color. The researchers compared the chromatic and achromatic hues used by the painters Matisse and Picasso with those used by the couturières Chanel and Vionnet, emphasizing the years 1918 through 1929. Using the Munsell color system as a framework, the researchers described the colors in eight paintings and 14 dresses in six collections. The researchers also made color counts in American Vogue for every year from 1918 through 1929, concentrating on the outerwear of Chanel and Vionnet. Colors were compared and contrasted for the painters and designers from 1918‐1924. Other compari sons were garments in fashion copy of 1918‐1924 with actual garments plus copy of 1925‐1929; and colors in paintings of 1918‐1924 with colors in dresses and copy, 1925‐1929. The researchers also reviewed literature for indications of painters' and designers' stated views on color and for their professional contacts with each other. Yellow red was the Munsell hue group much used by all four people across the span of the research. Overall, the designers favored the use of black and white, which were rarely found in the paintings. Blue was important to Picasso, Chanel, and Vionnet in 1918‐1924; both designers continued its use in 1925–1929.