Colour variation in standard soil-colour charts

Soil Research ◽  
2005 ◽  
Vol 43 (7) ◽  
pp. 827 ◽  
Author(s):  
M. Sánchez-Marañón ◽  
R. Huertas ◽  
M. Melgosa
Keyword(s):  
Analysis Of Variance ◽  
Colour Difference ◽  
Colour Space ◽  
Perception Threshold ◽  
Colour Variation ◽  
Standard Soil ◽  
Colour Changes ◽  
Cielab Colour

This paper presents colourimetric analyses of 6 standard soil-colour charts (1372 chips) from different manufacturers, editions, and degrees of use. The CIELAB hab, L*, and C*ab were found to have significant (analysis of variance, P < 0.05) variations among tested charts, and the Munsell hue, value, and chroma measured in most chips varied from their notation by as much as 1 unit. This discrepancy can be attributed to printing differences and/or colour fading. The Munsell loci of constant hue and chroma plotted in CIELAB colour space showed that colour fading is not uniform, so that visual steps between neighbouring chips change, and constant hue and chroma lines become deformed. The colour difference between chips identically designated in two charts ranged from 0.94 CIEDE2000 units (above perception threshold) for charts from the same manufacturer and degree of use, to 3.72 CIEDE2000 units for old charts from 2 different manufacturers. Chips from old charts became yellowish, darker, and less saturated. These colour changes are consistent with the responses of 10 observers who, on assessing 10 soil-colour samples, reported Munsell notations to have redder hue, lighter value and greater chroma. Periodic colourimetric checking of soil-colour charts would be advisable in order to avoid mistakes in soil-colour description.

scholarly journals Dependence of colour difference formulae on regular changes of colour coordinates in CIELAB colour space

2019 ◽  
Vol 70 (03) ◽  
pp. 248-254
Author(s):  
UGUR ONUR CINKO ◽  
BEHCET BEHCET BECERIR
Keyword(s):  
Empirical Study ◽  
Colour Difference ◽  
Colour Space ◽  
Special Software ◽  
Best Fitting ◽  
Coordinate Changes ◽  
Cielab Colour ◽  
Colour Coordinates

Four colour difference formulae [CIELAB (1976), CMC (2:1), CIE94 (2:1:1) and CIEDE2000 (2:1:1)] were assessed in CIELAB colour space for regular changes in colour coordinates. L*, a* and b* coordinates were changed regularly both as increasing and decreasing steps in different lightness and hue regions of the colour space. The dependence and consistency of the four formulae were researched depending on regular and constant colour coordinate changes. The aim of the empirical study was to determine if there could be a possibility of using different colour difference formulae in different hue regions of CIELAB colour space; in the region of bulk that each formula would give the best fitting and the most reliable results. The empirical study was carried out by using a special software which was prepared for the purpose. The results showed that CIELAB and CIE94 gave corresponding results with each other in the computing ranges. All the formulae showed different computing characteristics in the computation ranges. CMC formula gave the highest colour differences when computing near the grey point. It was concluded that CIEDE2000 formula suited itself the best according to the changes in computing steps. A more complicated software would be necessary to determine the sensitivity of the formulae by which the computing would be performed by changing all the coordinates (L*, a* and b*) at the same time.

scholarly journals Effect of Hairiness on Fabric Colour Characteristics

Tekstilec ◽  
2020 ◽  
Vol 63 (4) ◽  
pp. 276-286
Author(s):  
Kateryna Smykalo ◽  
◽  
Oksana Zakora ◽  
Keyword(s):  
Optical Properties ◽  
Human Perception ◽  
Raw Material ◽  
Colour Difference ◽  
Textile Materials ◽  
Textile Dyeing ◽  
Colour Changes ◽  
Cielab Colour ◽  
Colour Appearance

Designing the colour appearance of textiles requires taking into account their surface properties, hairiness among others. The villi protruding on the surface not only affect the quality of textile dyeing, but also largely determine its optical properties and the colour phenomenon. The analysis of studies of optical properties shows that the influence of hairiness on the phenomenon of colour is not well understood and that the amount of hairiness at which colour changes become significant for human perception remains indefinable. In this work, we studied the change in colour characteristics depending on the change in the hairiness of woollen fabrics, comparing “yarn – raw fabric”, “yarn – raised fabric”, “raw fabric – raised fabric”. Hairiness was estimated by the hairiness index, which was obtained from the analysis of sample microphotographs of yarn and fabric using software. The value of colour characteristics (lightness, chroma and colour difference) was measured in the CIELAB colour space (1976) using a spectrophotometer. The obtained experimental results showed that the changes in lightness and saturation of textile materials from the index of its hairiness are directly proportional. However, the value of changes is different for raw and napped fabrics, undyed and dyed samples, the initial colour hue and raw material composition also making certain adjustments. This study analysed the colour difference and established the level of variation in hairiness at which the colour mismatch between woollen fabrics becomes visually noticeable. The results of the study can be used to predict the colour and design the optical properties of fabrics for weaving and finishing.

scholarly journals A simple index to quantify and compare the magnitude of intraspecific geographic plumage colour variation in typical antbirds (Aves: Passeriformes: Thamnophilidae)

2020 ◽  
Vol 130 (2) ◽  
pp. 239-246
Author(s):  
Rafael S Marcondes ◽  
Robb T Brumfield
Keyword(s):  
Geographic Variation ◽  
Phenotypic Variation ◽  
Evolutionary Biology ◽  
Phylogeographic Structure ◽  
Plumage Colour ◽  
Colour Space ◽  
Colour Variation ◽  
Simple Index ◽  
High Prevalence ◽  
Variable Species

Abstract Intraspecific geographic phenotypic variation is a crucial theme in evolutionary biology. Comparing its magnitude across species can provide insights into its ecological and genetic correlates. Here, we developed an index, which we dub the V index, to quantify intraspecific plumage colour variation in typical antbirds (Thamnophilidae), a family which has long interested ornithologists due to a high prevalence of intraspecific variation. The V index is based on a bivariate colour space defined by brightness and redness. Its value for each species equals the mean area occupied by each of its subspecies in that colour space, divided by the area of the species. Lower values indicate greater intraspecific geographic variation. Based on this index, Thamnophilus caerulescens (Variable Antshrike) was exceptionally geographically variable compared to other thamnophilids, as previously suggested based on qualitative evidence. In general, we found that the most variable species had disjunct distributions and deep phylogeographic structure, suggesting an effect of historical population dynamics in producing geographic variation. The V index can be adapted for use with other taxa, traits, and taxonomic levels, and we expect it will instigate novel ways of thinking about phenotypic variation in birds and other animals.

Study on the Lightfastness of Ink Based on Visible and Infrared Spectral Analysis

2019 ◽  
Vol 11 (12) ◽  
pp. 1773-1780 ◽  
Author(s):  
Yan Zhang ◽  
Shisheng Zhou ◽  
Chan Li ◽  
Congjun Cao ◽  
Penggang Ren ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Polynomial Regression ◽  
Least Squares Method ◽  
Ageing Time ◽  
Nonlinear Least Squares ◽  
Colour Difference ◽  
Colour Variation ◽  
Three Samples ◽  
Infrared Spectral ◽  
Nonlinear Least Squares Method

A method based on visible reflection and infrared absorption spectroscopy is proposed to elucidate the colour variation law and mechanism of gravure ink in daylight. Three kinds of gravure spot colour ink, blue, red and cyan, are used for a xenon arc ageing experiment. The spectral reflectance of the samples is collected every 2 hours to analyse the variation in the chromaticity. A polynomial regression model of the colour difference and ageing time is established by the nonlinear least squares method. The coloration composition of the inks is analysed according to the infrared spectrum of the samples. The results show that in a 36-hour experiment with an illumination intensity of 550 W/m2, the lightfastness of the different colours of gravure spot ink is significant. The integrated value of the differential reflectance spectrum analysis shows that blue ink exhibits the largest change in chromaticity, followed by the red and cyan inks. The maximal colour differences of the three samples are 12.37, 4.78 and 1.34, respectively. A third-degree polynomial regression of the colour difference of the ink and ageing time achieves a good fitting result, with regression coefficients of 0.9700, 0.9980, and 0.9646, respectively. The infrared spectroscopy results show that the change in the chromaticity corresponds to changes in the molecular composition and absorption intensity of the pigments. The blue ink, with the largest change in chromaticity, exhibits the largest change in the absorption spectrum. The cyan ink, with inconspicuous changes in the chromaticity, exhibits the smallest change in the absorption spectrum. This research provides a more accurate theoretical basis for an analysis of the colour variation law and mechanism of gravure ink in daylight and provides a reference for lightfastness analysis of textiles, dyes and coatings.

scholarly journals Evaluation And Selection Of Colour Spaces For Digital Systems

2020 ◽  
pp. 86-94
Author(s):  
Vera L. Zhbanova
Keyword(s):  
Spectral Characteristics ◽  
Colorimetric Method ◽  
Digital Systems ◽  
Colour Difference ◽  
Colour Space ◽  
Digital Devices ◽  
Initial Stage ◽  
Photo Detectors ◽  
The Difference ◽  
Selection Of

The research examined the changing of colour difference by the control colours depending on the choice of colour space when working with matrix photo detector. The spectral characteristics of photo detectors from different manufacturers noticeably differ from each other and from the addition the difference in colour quality between different digital devices. A software method for studying the colour rendition of the image obtained by digital devices based on the selection of an individual colour space for each matrix photo detector is proposed. To analyze and evaluate the capabilities of the spectral characteristics of matrix photo detectors, the control colour method based on the Mansell Atlas was used. The analysis of the obtained parameters of 14 colours was carried out according to various criteria for seven colour spaces: sRGB, AdobeRGB, DCI-P3 RGB, M1N1P1, PAL / SECAM, Wide Gamut RGB, ProPhoto RGB. Also studied the influence of the choice of colour space on the change in the coordinates of the source 6,500 K. Based on the colour differences of the control colours, it is possible to choose the optimal colour space for working with a specific matrix photo detector. The latter will reduce colour distortion at the initial stage of image registration. The ways for improving the colorimetric method of control colours are proposed as applied to digital devices at the software level.

scholarly journals Preferred skin reproduction centres for different skin groups

2020 ◽  
Vol 2020 (28) ◽  
pp. 109-113
Author(s):  
Rui Peng ◽  
Ming Ronnier Luo ◽  
Mingkai Cao ◽  
Yuechen Zhu ◽  
Xiaoxuan Liu ◽  
...  
Keyword(s):  
Ethnic Groups ◽  
South Asian ◽  
Skin Colour ◽  
Psychophysical Experiment ◽  
Colour Centre ◽  
Colour Space ◽  
Colour Centres ◽  
Darkened Room ◽  
Cielab Colour ◽  
Facial Images

Producing preferred skin colours is vital for the digital images on mobile phone manufacturers. Previous studies investigated the skin colours only in chromatic plane excluding lightness. A psychophysical experiment was conducted to determine preferred skin colour centres for different skin colour types on mobile displays in a darkened room. Ten facial images were selected for the experiment to cover different skin colour types (Caucasian, Oriental, South Asian and African). A set of 49 predetermined colour centres uniformly sampled within the skin colour ellipsoid in CIELAB colour space was used to morph skin colours of test images. Thirty observers from each of the 3 ethnic groups (Caucasian, Oriental and South Asian) participated in the experiment. The preferred skin colour centre and region in the form of ellipsoid for each skin group were reported. It was found that the preferred colour centres from different skin colour types were very similar except their lightness as expected, and were also quite similar between the observers from different ethnic groups.

scholarly journals A computational framework for colour metrics and colour space transforms

2016 ◽  
Vol 2 ◽  
pp. e48 ◽  
Author(s):  
Ivar Farup
Keyword(s):  
Main Idea ◽  
Object Oriented ◽  
Colour Difference ◽  
Colour Space ◽  
Computational Framework ◽  
Class Hierarchy ◽  
Computational Overhead ◽  
Python Programming Language ◽  
Python Programming ◽  
Metric Tensors

An object-oriented computational framework for the transformation of colour data and colour metric tensors is presented. The main idea of the design is to represent the transforms between spaces as compositions of objects from a class hierarchy providing the methods for both the transforms themselves and the corresponding Jacobian matrices. In this way, new colour spaces can be implemented on the fly by transforming from any existing colour space, and colour data in various formats as well as colour metric tensors and colour difference data can easily be transformed between the colour spaces. This reduces what normally requires several days of coding to a few lines of code without introducing a significant computational overhead. The framework is implemented in the Python programming language.

scholarly journals A colorimetric comparison of sunless with natural skin tan

2020 ◽  
Author(s):  
Kinjiro Amano ◽  
Kaida Xiao ◽  
Sophie Wuerger ◽  
Georg Meyer
Keyword(s):  
Principal Component ◽  
Critical Factor ◽  
Skin Colour ◽  
Control Group ◽  
Naturally Occurring ◽  
Median Error ◽  
Natural Range ◽  
Colour Changes ◽  
The Difference ◽  
Cielab Colour

AbstractThe main ingredient of sunless tanning products is dihydroxyacetone (DHA). DHA reacts with the protein and amino acid composition in the surface layers of the skin, producing melanoidins, which changes the skin colour, imitating natural skin tan caused by melanin. The purpose of this study was to characterise DHA-induced skin colour changes and to test whether we can predict the outcome of DHA application on skin tone changes.To assess the DHA-induced skin colour shift quantitatively, colorimetric and spectral measurements of the inner forearm were obtained before, four hours and 24 hours after application of a 7.5% concentration DHA gel in the experimental group (n = 100). In a control group (n = 60), the same measurements were obtained on both the inner forearm (infrequently sun-exposed) and the outer forearm (frequently sun-exposed); the difference between these two areas was defined as the naturally occurring tan. Skin colour shifts caused by DHA tanning and by natural tanning were compared in terms of lightness (L*), redness (a*) and yellowness (b*) in the standard CIELAB colour space. Naturalness of the DHA-induced skin tan was evaluated by comparing the trajectory of the chromaticity distribution in (L*, b*) space with that of naturally occurring tan. Twenty-four hours after DHA application, approximately 20% of the skin colour samples became excessively yellow, with chromaticities outside the natural range in (L*, b*) space. A principal component analysis was used to characterise the tanning pathway. Skin colour shifts induced by DHA were predicted by a multiple regression on the chromaticities and the skin properties. The model explained up to 49% of variance in colorimetric components with a median error of less than 2 ΔE. We conclude that the control of both the magnitude and the direction of the colour shift is a critical factor to achieve a natural appearance.

The effect of UV radiation in Xenotest 450 on the colour of steamed beech wood during the process of simulated ageing

2019 ◽  
Vol 106 ◽  
pp. 114-120
Author(s):  
LADISLAV DZURENDA
Keyword(s):  
Uv Radiation ◽  
Wave Length ◽  
Beech Wood ◽  
Exposure Period ◽  
Rate Of Change ◽  
Accelerated Ageing ◽  
Colour Difference ◽  
Colour Space ◽  
Yellow Colour ◽  
Hue Angle

The effect of UV radiation in Xenotest 450 on the colour of steamed beech wood during the process of simulated ageing .The aim of the paper is to present the changes in colour of steamed beech wood in the pocess of simulated ageing in Xenotest 450. Red-brown colour of beech wood with the coordinates of L* = 62.6 ± 2.8; a* = 10.9 ± 2.3; b* = 17.1 ± 1.3 in the CIE L*a*b* colour space resulted from the mode of colour modification of wood with saturated vapour with the temperature of t = 120 ± 2 oC for τ = 6.5 hours. The surface of samples after drying to the moisture content of w = 12 % and planing was irradiated in Xenotest 450 with xenon gasdischarge tube by UV radiation with the wave length of 340 nm. Accelerated ageing experiment ran in exposure period A1 for seven days. Simulated ageing of thermally treated beech wood showed that due to UV radiation, the wood surface is turning pale and brown. The change in the lightness coordinate by the value of ΔL* = + 6.7 shows the rate of change in the surface lightness and the changes in the values of chromatic coordinates of red colour by the value of Δa* = - 0.1 and yellow colour by Δb* = + 12.3 shows the rate of getting brown. Therefore the hue angle increases from h*ab = 57.5 ° to h°ab = 69.8 °. The value of the total colour difference resulting from the process of ageing is ΔE* = 14.5.

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