Munsell Hue Research Articles

Warm/cool judgments as a function of hue, value, and chroma

Besides conventional perceptual attributes of hue, brightness, and saturation, colors are universally classified along a warm/cool dimension. Previous estimates of how warm/cool values are distributed across color space have relied on subjective ratings. Here we employed simple ordinal judgments between stimulus pairs using maximum likelihood conjoint measurement (MLCM) to assess the influence of Munsell hue, value, and chroma on warm/cool judgments. We also evaluated an identification task for single stimulus presentations. For the MLCM procedure, observers judged on each trial which of the two stimuli appeared warmer. For the identification task, observers classified individually presented color patches as cool or warm. The judgments were analyzed with probit regression to estimate the underlying perceptual scale values. The results confirm that the contributions of different dimensions to warm/cool variations in color space can be estimated using only ordinal judgments. While for most observers, warm/cool judgments depended on hue, there were individual variations in the extent to which value contributed to warm/cool, and little evidence for an effect of chroma.

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.

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.

Analysis of Rock Mass Surface Colour using CIELAB and Munsell Chart

Rock mass surface colour is crucial for weathering assessment. CIELAB colour space and Munsell chart are methods to express the surface colour of rock masses. This study analysed the L*a*b* value from both approaches and examined the effectiveness and reliability of rock slope weathering assessment method. The Munsell Rock chart is a conventional method primarily used in practice. However, due to the constraint of individual vision and variation in the optical environment, errors and bias in rock surface colour can easily occur using the conventional method. The colourimeter was used to determine the CIELAB colour values of the samples, while the rock colour chart determined the colour coordinates and Munsell values. The Munsell hue and chroma were assigned using linear interpolation by Munsell conversion software CMC 2.1 to convert Munsell colour systems to L*a*b* value. A total of six granitic rock slopes were investigated. For quantitatively method, the Munsell optical system was less effective in assessing the rock mass surface colour. The positive correlation of a* and b* with R2=0.9407 demonstrated the efficiency of CIELAB system. The a*b* result of the rock slope indicated that most of the slopes were considered medium to strong with a moderately weathered surface. This result is strongly supported by a geomechanical test of Schmidt-UCS and index properties (Id2) with a range of 50-100 MPa and 2-4 MPa respectively. The finding verified mineralogical assessment which showed the correlation of rock mass surface colour to mineral composition. The study recommended any geotechnical and technical purpose in enhancing the method of weathering assessment by using the CIELAB colour space to rapidly and efficiently measure the rock surface colour.

Color representations of normals and congenital red–green color deficiencies: Estimation of individual results based on color vision model

AbstractDifference scaling experiment was conducted to investigate the mental color representation of congenital color‐deficient observers and observers with normal color vision. Two decks of cards, high and medium chroma, each containing 10 Munsell chips, were prepared. A total of 45 pairs of hues were prepared for each of the decks. Ten protans, 10 deutans, and 10 people with normal color vision participated as observers, with each asked to rate the perceptual distance between two colors on a given color card. The results were analyzed using the multidimensional scaling method. All observers with normal color vision showed a circular shape close to the Munsell hue circle, while the majority of color‐deficient observers showed a concave shape bending at Y and PB. To indicate the degree of distortion from a circle, the distortion index was proposed to quantitatively evaluate intergroup and individual differences. To investigate the underlying mechanism of intergroup differences as well as individual differences in color representations of observers with normal color vision and color‐deficient observers, we proposed a model that considers various levels of human color vision mechanism from the cone pigment absorption, the luminance and opponent‐color coding level, and nonlinear transformation to difference‐scaling judgment. The circular shape for observers with normal color vision and some color‐deficient observers, as well as concave shapes for most color‐deficient observers were estimated. The correlation coefficient between the estimation and experiment‐based difference ranged from r = 0.64 to r = 0.94 with the grand average of r = 0.82, with p‐values less than 0.001 for all observers, suggesting that the concept of proposed model is appropriate.

Water-stained leaves: formation and application as a field indicator of wetland hydrology

Wetland delineations conducted in the United States utilize field indicators as proxy measures of the presence or absence of wetland hydrology. Water-stained leaves provide a practical, qualitative field indicator of wetland hydrology; however, the formation of water-stained leaves has not been elucidated. In response, leaves from six tree species were examined under five treatments to investigate the water-staining process and concomitant timeframes. Results indicate that leaf staining occurred within 14-21 days of continuous exposure to wetland waters and sediment under both laboratory and field conditions. Leaf staining was characterized by readily observable shifts in leaf color (i.e., decreasing Munsell hue, value, and chroma) causing the leaves to appear very dark or black. No color shifts associated with leaf staining occurred in treatments exposed to upland conditions. The timeframe associated with leaf staining corresponds with established wetland hydrology criteria requiring a minimum hydroperiod of 14 consecutive days of soil saturation, flooding, or ponding. Leaves exposed to wetland waters and sediment underwent color shifts significantly faster and to a greater extent than leaves inundated with deionized water, likely as a result of increased microbial abundance and the presence of anaerobic conditions in the simulated wetland treatments. Results suggest that water-stained leaves 1) are a useful and reliable wetland hydrology field indicator for wetland delineation purposes, 2) may provide a proxy measure of wetland hydroperiod, and 3) Munsell color measurements can help differentiate between leaves exposed to wetland and upland conditions.

Soil Color and Mineralogy Mapping Using Proximal and Remote Sensing in Midwest Brazil

Soil color and mineralogy are used as diagnostic criteria to distinguish different soil types. In the literature, 350–2500 nm spectra were successfully used to predict soil color and mineralogy, but these attributes currently are not mapped for most Brazilian soils. In this paper, we provided the first large-extent maps with 30 m resolution of soil color and mineralogy at three depth intervals for 850,000 km2 of Midwest Brazil. We obtained soil 350–2500 nm spectra from 1397 sites of the Brazilian Soil Spectral Library at 0–20 cm, 20–60, and 60–100 cm depths. Spectra was used to derive Munsell hue, value, and chroma, and also second derivative spectra of the Kubelka–Munk function, where key spectral bands were identified and their amplitude measured for mineral quantification. Landsat composites of topsoil and vegetation reflectance, together with relief and climate data, were used as covariates to predict Munsell color and Fe–Al oxides, and 1:1 and 2:1 clay minerals of topsoil and subsoil. We used random forest for soil modeling and 10-fold cross-validation. Soil spectra and remote sensing data accurately mapped color and mineralogy at topsoil and subsoil in Midwest Brazil. Hematite showed high prediction accuracy (R2 > 0.71), followed by Munsell value and hue. Satellite topsoil reflectance at blue spectral region was the most relevant predictor (25% global importance) for soil color and mineralogy. Our maps were consistent with pedological expert knowledge, legacy soil observations, and legacy soil class map of the study region.

Relating Munsell to other systems in an elastic colour solid

AbstractFor a student of architecture in 1958, the Munsell system was a revelation. Munsell's hue, value, and chroma were perfectly clear, but then they were challenged by the Ostwald system with its white content and black content. The revelation was followed by confusion. It became evident that there is no such thing as a single “correct” colour solid or, indeed, a single “correct” colour circle. Colour circles can be structured with equally spaced “primaries” or organized so that “complementary” colours are opposite to each other, but different systems have different sets of primaries, and the different ways of establishing complementary relationships yield different pairings. These different relationships can be reconciled if the circle is treated as elastic with intervals between colours stretched or compressed to show the relationships relevant for a given situation. In the third dimension of a colour solid, the principle of elasticity can also be applied to show relationships of value, of whiteness and blackness, and other dimensions as they are variously defined. The structure of Munsell can be “morphed” into that of Ostwald and other systems where colours are ordered according to different principles. If the colour solid is regarded as elastic, it is easier to understand the information embodied in the structures of different colour order systems and also to see how they relate.

Formation and characterization of ternary (Na, NH4, H3O)-jarosites produced from Acidithiobacillus ferrooxidans cultures

The purpose of this study was to characterize a series of (Na, NH4, H3O)-jarosites produced with various combinations of NH4+ + Na+ in cultures of Acidithiobacillus ferrooxidans that simulated acid solutions from bioleaching systems. The solution concentrations utilized were 6.1, 80, 160 and 320 mM for NH4+ and 0, 50, 100, 250 and 500 mM for Na+ as their respective sulfates. Media at pH 2.2 were inoculated with iron-oxidizing A. ferrooxidans and incubated in shake flasks at 22 ± 2 °C. As the bacteria oxidized ferrous sulfate, ferric iron hydrolyzed and precipitated as schwertmannite (idealized formula Fe8O8(OH)6(SO4).nH2O) and/or as solid solution jarosites [(Na, NH4, H3O)-Fe3(SO4)2(OH)6)] depending on the relative and absolute concentrations of NH4+ and Na+. The precipitates were characterized by elemental analysis, X-ray diffraction, specific surface area, and Munsell color. Schwertmannite was the dominant mineral product at low combinations of Na+ (≤50 mM) and NH4+ (≤80 mM) in the media after 2 weeks of aging. At higher single or combined concentrations and with aging for 6 and 11 weeks, the formation of yellowish, solid solution jarosites was enhanced. Precipitation of jarosite-group minerals was favored by NH4+ relative to Na+. Color (Munsell hue) was a useful tool for assessing sample mineralogy after extended aging, but the presence of abundant, poorly crystalline schwertmannite tended to mask the color of admixed jarosite-group minerals after only 2 weeks of contact with the culture media. The purest samples of jarosite-type minerals had specific surface areas <1.0 m2/g. Unit cell edge lengths and cell volume calculations from powder XRD data indicated that the jarositic phases produced were ternary (Na, NH4, H3O)-solid solutions. Most products also appeared to be deficient in structural Fe, especially at low NH4 contents. Thus, ferric iron precipitation from the simulated bioleaching systems yielded solid solutions of jarosites with chemical compositions that were dependent on the relative concentrations of Na+ and NH4+ in the synthesis media. No phase separations involving discrete, end-member Na-, NH4-, or H3O-jarosites were detected.

Long‐term changes in Japanese women's facial skin color

AbstractIt has been suggested that skin color changes not only with advancing age but also with the times. The purpose of this study was to investigate changes in Japanese women's facial skin color over 25 years, as well as the changes in skin pigmentation that affect skin color. First, skin color changes in terms of Munsell color values were investigated. A total of 3181 Japanese women residing in the greater Tokyo area were enrolled, and datasets were collected using spectrophotometers, designated as the 1991, 2001, 2005, and 2015 data. The mean Munsell hue, value, and chroma were calculated for each measurement year. Next, the concentrations of melanin and hemoglobin were calculated from spectral data, to investigate changes in skin pigmentations. Finally, Monte Carlo simulations were performed to verify that the suggested changes in skin pigmentations brought about skin color changes. As a result, skin color significantly changed toward high lightness, low saturation, and high yellowness from the 1991 data to the 2001 data. From the 2005 to 2015 data, the skin color distribution shifted toward lower saturation and increased redness. In addition, the concentration of hemoglobin decreased significantly from the 1991 data to the 2001 data, while the melanin concentration decreased significantly from the 2005 data to the 2015 data.

Using UAS Hyperspatial RGB Imagery for Identifying Beach Zones along the South Texas Coast

Shoreline information is fundamental for understanding coastal dynamics and for implementing environmental policy. The analysis of shoreline variability usually uses a group of shoreline indicators visibly discernible in coastal imagery, such as the seaward vegetation line, wet beach/dry beach line, and instantaneous water line. These indicators partition a beach into four zones: vegetated land, dry sand or debris, wet sand, and water. Unmanned aircraft system (UAS) remote sensing that can acquire imagery with sub-decimeter pixel size provides opportunities to map these four beach zones. This paper attempts to delineate four beach zones based on UAS hyperspatial RGB (Red, Green, and Blue) imagery, namely imagery of sub-decimeter pixel size, and feature textures. Besides the RGB images, this paper also uses USGS (the United States Geological Survey) Munsell HSV (Hue, Saturation, and Value) and CIELUV (the CIE 1976 (L*, u*, v*) color space) images transformed from an RGB image. The four beach zones are identified based on the Gray Level Co-Occurrence Matrix (GLCM) and Local Binary Pattern (LBP) textures. Experiments were conducted with South Padre Island photos acquired by a Nikon D80 camera mounted on the US-16 UAS during March 2014. The results show that USGS Munsell hue can separate land and water reliably. GLCM and LBP textures can slightly improve classification accuracies by both unsupervised and supervised classification techniques. The experiments also indicate that we could reach acceptable results on different photos while using training data from another photo for site-specific UAS remote sensing. The findings imply that parallel processing of classification is feasible.

An exploration of 2.5D printing as tactile pictures

Novel printing and layering technologies that incorporate a raised or embossed surface have demonstrated new opportunities for novel applications. Textured images have been used extensively in the print industry as decorative decals and embellishments to enhance the surface qualities of packaging and prints. As the resolution and print quality has improved, and the technology has become more accessible, there are now more opportunities to explore texture in artworks, especially in relation to tactile printing for blind or visually impaired. Over the last two decades, museums have broadened the idea of cultural accessibility for blind people, for example, to cultural events and museums. Access to knowledge began by enabling users to engage with texts and printed word, and then as second hand experience through audio books and description about artefacts and events, and now the opportunity to give access to images, such as artworks, picture books and photographs, in museums whereby a second hand experience is replaced by first hand experience. On a practical level, day-to-day understanding of identifying information and things, ways of identifying colour and colour relationships has been developed by Okudera (2015) in the form of textile tags to convey colour information is a practical method to enable blind people to identify the colour of their clothes and to know that their clothes colour co-ordinated. A simple iron on tactile tag, based on the hue circle, enabled users to identify colour relationships. Ten small raised (rubber to the touch) dots are arranged around a Munsell hue circle each representing primary colours, along with three raised vertical dots in the centre to represent white, grey and black. In order to identify the representative colour, a bigger dot or hole is punctured into the tag (Okudera). Tactile pictures for blind can provide an enhanced understanding for the user. Appropriate methods for image segmentation is necessary to distinguish different parts of a picture. Traditional approaches use contours and patterns, which creates a distinct and recognisable shape and enables separate objects to identified. A contour arises on the boundary between two surfaces and is usually described by a line. Different textures can also be incorporated to convey an idea of a picture. Living Paintings provide touch to see pictures, which can range from current events such as the Olympics to educational books such as dinosaurs to cultural object such as from the British Museum London. These relief tactile pictures use highly simplified shapes, but provide essential unambiguous information. The pages are vacuum formed using thermo plastic sheet over a carved or machined board, and then ring bound together with other pages to form a flip-book. This cheap method means that books can be mass-produced, widely circulated, and are fairly robust. However, we would argue that accuracy is not even wanted in most of the applications, as a certain degree of interpretation of the full body of things may be more valuable and welcome than a cold replica. An interesting project, where interpretation and exploration is fundamental, is demonstrated by Studios Durero. The Didu project in collaboration with the Prado Madrid, has attempted to make classic paintings accessible to visually impaired people through relief prints. Their designers worked alongside art specialists and with visually impaired people to understand how to either exaggerate textures already present in a painting, or to create new ones that would be visually relevant but needed to be exaggerated to be perceived by blind participants. Likewise 3D Photoworks have studied how to make fine art prints accessible by building a high-relief surface of paintings, and Tooteko use sound and touch to assist the user to explore a range of images. This short presentation will discuss aspects and requirements of relief, tactile 2.5D printing, and surface manufacturing in relation to tactile printing for the visually impaired.

Soil-color changes by sulfuricization induced from a pyritic surface sediment

Colors are widely used to describe hydroxysulfate minerals and acid sulfate soils but seldom to study an active sulfuricization process. Our research was designed to measure the spectrophotometric colors of a soil sulfuricized by pyritic sediment over 15years (8 profiles, 75 samples) and to determine whether color could be employed to identify the new soil materials. The Munsell value of gray sulfidic materials deposited on the soil surface changed over time from 3.0 to 5.6 (R2=0.97) because of Fe leaching and the formation of whitish sulfates. The underlying native soil was first pigmented yellowish brown by illuvial precipitates appearing in SEM as “bubble wrap” coating soil particles and having the EDX peaks of Fe, S and O, and the XRD peaks at 0.255 and 0.166nm. Between pH values 3 and 4 its spectral character in the second-derivative Kulbelka–Munk function registered a maximum at 440nm and a minimum at 480nm, both drastically attenuated after oxalate Fe-extraction. Therefore, we attributed most of precipitates to schwertmannite phases. Their subsequent progressive transformation to jarosite in parallel to a pH decline was colorimetrically detected by a displacement of the spectral maximum to 450nm, its intensity reduction with increasing jarosite content, and yellowing of aggregates and ground-soil samples from 8.5YR to 0.2Y. Finally, the dominance of jarosite below pH2.4 resulted in soil materials with a spectral minimum at 440nm and Munsell hue between 1.3Y and 5.3Y. Because sulfidic, schwertmannitic, and jarositic materials, as well as their compositional changes, were unambiguously identified, soil sulfuricization could be determined by colorimetry.

시판 쪽잎 분말의 쪽 염료에의 활용을 위한 염색성 향상 연구

Abstract This research investigated the effective conditions to dye cotton with commercial indigo leaf powder. Wetested dyeing conditions of: pH of dyebath (6.5, 9-12), heating (20 o C, 50 o C, 70 o C, 90 o C), ageing (0, 0.5, 1,4, 24 hours), reduction time (0, 30, 60 min), and dyeing temperature (2 o C, 10 o C, 20 o C, 50 o C, 70 o C, 80 o C),dyeing was conducted for 20 minutes. The highest K/S value was obtained when cotton was dyed using pH11 dyebath, heated at 50 o C for 30 minutes, aged for 24 hours at room temperature (20 o C), reduction carriedout for 30 minutes, and dyed at 50 o C. It is proposed that the K/S value is primarily influenced by the dye-bath pH and dyeing temperature, followed by the presence or absence of ageing time and reduction time.The color of cotton with high K/S values was B type by Munsell hue value, which was similar to the colorobtained in previous studies by freshly made indigo leaf powder and indigo leaf juice. The results indicatethat the dyeing conditions established in this research are suitable to maximize the dyeability of commercialindigo leaf powder and that the indigo leaf powder can be used as a substitute for fresh indigo leaf juice.Key words: Indigo leaf powder, pH of dyebath, Heating temperature, Ageing time, Dyeing temperature;쪽잎 분말, 염액의 pH, 가열온도, 방치시간, 염색온도

Synthesis and properties of ternary (K, NH4, H3O)-jarosites precipitated from Acidithiobacillus ferrooxidans cultures in simulated bioleaching solutions

The purpose of this study was to synthesize a series of solid solution jarosites by biological oxidation of ferrous iron at pH2.2–4.4 and ambient temperature in media containing mixtures of K+ (0, 1, 4, 6, 12, 31mM) and NH4+ (6.1, 80, 160, 320mM). The starting material was a liquid medium for Acidithiobacillus ferrooxidans comprised of 120mM FeSO4 solution and mineral salts at pH2.2. Following inoculation with A. ferrooxidans, the cultures were incubated in shake flasks at 22°C. As bacteria oxidized ferrous iron, ferric iron hydrolyzed and precipitated as jarosite-group minerals (AFe3(SO4)2(OH)6) and/or schwertmannite (idealized formula Fe8O8(OH)6(SO4)·nH2O). The precipitates were characterized by X-ray diffraction (XRD), elemental analysis, and Munsell color. Schwertmannite was the dominant mineral product at low combinations of K+ (≤4mM) and NH4+ (≤80mM) in the media. At higher single or combined concentrations, yellowish jarosite phases were produced, and Munsell hue provided a sensitive means of detecting minor schwertmannite in the oxidation products. Although the hydrated ionic radii of K+ and NH4+ are similar, K+ greatly facilitated the formation of a jarosite phase compared to NH4+. Unit cell and cell volume calculations from refinements of the powder XRD patterns indicated that the jarosite phases produced were mostly ternary (K, NH4, H3O)-solid solutions that were also deficient in structural Fe, especially at low NH4 contents. Thus, ferric iron precipitation from the simulated bioleaching systems yielded solid solutions of jarosite with chemical compositions that were dependent on the relative concentrations of K+ and NH4+ in the synthesis media. No phase separations involving discrete, end-member K-jarosite or NH4-jarosite were detected in the un-aged precipitates.

Comparison of Munsell Soil Color Charts and the GLOBE Soil Color Book

Color is a commonly measured morphological property determined during field investigations of soils. Consequently, a soil color book is among the equipment carried by almost every field soil scientist. Our objective was to determine if there was a significant difference between the color representations of two color references: the Munsell Soil Color Charts and the GLOBE Soil Color Book. Using 10 new copies of each brand of book, Munsell hue, value, and chroma were measured for all color chips. Standard thresholds for soil color contrast (faint, distinct, prominent) were used to assess if the measured color differed from the reported color of each chip. Of 4020 measurements, only 28 had a non-faint contrast. Statistically, there was mild evidence to suggest a difference between color representations of the two brands, but this was attributable to discrepancies for a single chip. For all other chips, there was no significant difference between the brands.

Using the mobile phone as Munsell soil-colour sensor: An experiment under controlled illumination conditions

Soil colour has been determined in most cases by using Munsell soil-colour charts, sometimes with spectrometers, and occasionally with digital cameras. The objective here is to assess whether a mobile phone, which has all the requirements to capture and process digital images, might also be able to provide an objective evaluation of soil colour under controlled illumination. For this, we have developed an Android application that takes a picture of a soil sample, allowing the user to select the region of interest and then, after a RGB image-processing and a polynomial process transform between colour spaces, the Munsell (HVC) and CIE (XYZ) coordinates appear on the screen of mobile phone. In this way, a commercial HTC smartphone estimated the colour of 60 crumbled soil samples between 2.9YR and 2.3Y with a mean error of 3.75±1.81 CIELAB units, taking as a reference the colour measurements performed with a spectroradiometer. The Munsell hue had the worst estimates (mean error of 2.72±1.61 Munsell units) because of its geometric mismatch with the RGB colour space and for being defined to illuminant C, different of the D65 source under which the phone camera took the pictures. Because the measuring errors were lower than those described in the literature for the visual determination of soil colour, and the application also worked successfully in a different smartphone than the one used in its development, we think that current experimental results encourage the expectations of using smartphones in the field as soil-colour sensors.

A Robust Hue Descriptor

A hue descriptor based on Logvinenko's illuminantinvariant object colour atlas [1] is tested in terms of how well it maps hues to the hue names found in Moroney's Colour Thesaurus [2] [3] and how well it maps hues of Munsell papers to their corresponding Munsell hue designator. Called the KSM hue descriptor, it correlates hue with the central wavelength of a Gaussian-shaped reflectance function. An important feature of this representation is that the set of hue descriptors inherits the illuminate invariant property of Logvinenko's object colour atlas. Despite the illuminant invariance of the atlas and the hue descriptors, metamer mismatching means that colour stimulus shift [4] can occur, which will inevitably lead to some hue shifts. However, tests show that KSM hue is robust in the sense that it is much more stable under a change of illuminant than CIELAB hue.

Color constancy investigated via partial hue-matching

Each hue is believed to be made up of the four component hues (yellow, blue, red, and green). A hue consisting of just one component hue is called unitary (or unique). A new technique--partial hue-matching--has been used to reveal the component and unitary hues for a sample of 32 Munsell papers, which were illuminated by neutral, yellow, blue, green, and red lights and assessed by four normal trichromatic observers. The same set of four component hues has been found under both the neutral and the chromatic illuminations for all of the observers. On average, more than 87% of the papers containing a particular component hue under the neutral illumination also have this component hue when lit by the chromatic lights. However, only a quarter of the papers perceived as unitary under the neutral illumination continues being perceived as unitary under all of the chromatic illuminations. In other words, most unitary colors shift along the hue circle due to change in an illuminant's chromaticity. Still, this shift of unitary colors is relatively small: On average, it does not exceed one Munsell hue step.

The effect of hue on the perception of blackness using munsell samples

Although black is an important color, the perception of black objects has not been systematically examined. The purpose of this work was to determine the influence of hue on the perception of preferred blackness. A set of 20 glossy low chroma Munsell sheets were purchased comprising a complete hue circle with a value and chroma of two and one, respectively (L* = 19.3–20.75, and C* = 3.66–6.58). The Munsell samples were divided into two interleaved groups: (5R, 5YR, 5Y, 5GY, 5G, 5BG, 5B, 5PB, 5P, and 5RP) and (10R, 10YR, 10Y, 10GY, 10G, 10BG, 10B, 10PB, 10P, and 10RP). Fifty color‐normal observers force‐ranked the two sets of 10 samples from “most like black” to “least like black.” Observers then assessed a set of six samples that represented the three samples from each set of 10 that the observer chose to be “most like black.” The 50 observers were found to have fairly good autoconcordance and concordance values. In repeat experiments observers agreed with themselves in 81% of the pairwise decisions, and they agreed with the grand mean rank 76% of the time. The blue–green samples (with Munsell hue notations 10G, 5BG, and 10BG) were most selected (and were considered blackest), followed by green, blue, and purple–blue. The samples selected the fewest times by any observer as being most black were the red samples. The grand mean rankings demonstrate that greenish to bluish blacks are perceived by the observers as “blacker” than yellowish and reddish blacks. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 423–428, 2013