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.

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 The Origin of Sand and Its Colour on the South-Eastern Coast of Spain: Implications for Erosion Management

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 377 ◽  
Author(s):  
Asensio-Montesinos ◽  
Pranzini ◽  
Martínez-Martínez ◽  
Cinelli ◽  
Anfuso ◽  
...  
Keyword(s):  
Western Mediterranean ◽  
Mediterranean Coast ◽  
Eastern Coast ◽  
Storm Events ◽  
Colour Space ◽  
Source Areas ◽  
Beach Width ◽  
Severe Erosion ◽  
Colour Coordinates ◽  
Economic Function

Sand colour can give important information about mineral composition and, consequently, sediment source areas and input systems. Beach appearance, which is mostly linked to sand colour, has a relevant economic function in tourist areas. In this paper, the colour of 66 sand samples, collected along both natural and nourished beaches in the western Mediterranean coast of Spain, were assessed in CIEL*a*b* 1976 colour space. The obtained results showed relevant differences between natural and artificially nourished beaches. The colour of many nourished beaches generally differs from the native one because the origin of the injected sand is different. The native sand colour coordinates’ range is: L* (40.16–63.71); a* (−1.47–6.40); b* (7.48–18.06). On the contrary, for nourished beaches’ the colour range is: L* (47.66–70.75); a*(0.72‒5.16); b* (5.82–18.82). Impacts of beach nourishment on the native sand colour were studied at San Juan beach, the most popular one along the study area. Nourishment works were performed after severe erosion, usually linked to anthropic activities/structures and storm events, but also to increase beach width and hence benefit tourism.

scholarly journals The effect of storage on the colour of paprika powders with added oleoresin

2016 ◽  
Vol 9 (1) ◽  
pp. 50-59
Author(s):  
Zs. H. Horváth
Keyword(s):  
Natural Food ◽  
Colour Measurements ◽  
Food Colour ◽  
Powder Samples ◽  
Paprika Oleoresin ◽  
Colour System ◽  
Plant Grown ◽  
Cielab Colour ◽  
Colour Coordinates ◽  
Food Colours

Abstract The use of natural food colours is preferred to that of arti­ficial dyestuffs for modern alimentary purposes. Paprika is a spice plant grown and consumed in considerable quantities worldwide and also used as a natural food colour, so the colouring power of powders is very important. The colour of paprika powder is highly relevant too because the consumer concludes its colouring power based on its colour. The colouring power of paprika powders is directly determined by the quality and quantity of the colouring agent of paprika. The paprika oleoresin, that is an oil soluble extract from the fruits of Capsicum Annum Linn or Capsicum Frutescens, is suitable to raise the colour agent content of paprika powders. We investigated how the colour and the characteristics of paprika powder samples with added oleoresin change in the course of storage. The colour agent content of 7 different quality powders was increased with 7-75% using oleoresin. The initial colour agent content of samples changed between 41 and 169 ASTA units. The powders were made from Chinese, Peruvian, and Hungarian paprika. Colour measurements were performed with a HunterLab MiniScan colour-measuring instrument. The CIELab colour system was used for colour characterization. The colour agent content and the colour coordinates of samples were measured throughout 9 months. The decrease of colour agent con­tent varied between 22 and 51 percent, while the average reduction was 33 percent. The quantity of added oleoresin did not influence the colour agent content decrease significantly. The values of colour difference changed between 2 and 4.5 units. The initial paprika powder influenced the variation significantly, but the quantity of added oleoresin did not have a significant effect.

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 Analysis of change of the colour parameters of paprika powder with different added oleoresin

2013 ◽  
Vol 7 (1-2) ◽  
pp. 16-21
Author(s):  
Zsuzsanna H. Horváth
Keyword(s):  
Natural Food ◽  
Degree Function ◽  
Food Colour ◽  
Important Sense ◽  
Powder Samples ◽  
Colour Parameters ◽  
Hue Angle ◽  
Cielab Colour ◽  
Colour Coordinates ◽  
Second Degree

The instrumental colour measurement isn’t used in course of the making and the qualification of the paprika powder, although the colour is the most important sense property of its. Paprika is also used as a natural food colour. The colour of paprika powder is very important too, because the consumer concludes its colouring power based on its colour. The colouring power is determined by quality and quantity of colouring agent of paprika squarely. The colour of the powder is influenced by its particle size, oil content and moisture content and first of all the colour agent content.We investigated how the colour agent content increasing influences the colour characteristics of paprika powders. The L*, a*, b* colour coordinates defined in the CIELab colour space were applied for the colour characterization. The measurements were carried out using a Minolta CR-300 tristimulus colour analyser.We loosed the colour agent from the paprika powder samples using acetone. The colour agent content of obtained samples was less than 10 ASTA units. After different quantity of oleoresin ( 0.0186 g, 0.0461 g, 0.0626 g, 0.0953 g, 0.3500 g, 0.6399 g) was added to samples of 10 g of powder. The colour characteristics and colour agent content of these samples were determined. The relation between colour agent content and colour coordinates was analysed using regression analysis and the colour differences ΔE*ab were determined between samples with different colour agent content.The results depicted that L* lightness coordinate decreased with increasing colour agent content, the points fitted on a reciprocal function with a significant correlation ( p=0.01). In the case of a* redness coordinate the points fitted on a saturation function (0.01), the redness coordinate didn’t change above 129 ASTA units. The b* yellowness coordinate increased to 97 ASTA units, then decreased, the points fitted on a second degree function with a significant correlation (p=0.01). The function has maximum at 97.17 ASTA units; the maximum value was 25.22 coordinate units. The value of hue angle (hoab) progressively decreased while the colour agent content was added. The C*ab chroma increased to 121 ASTA units, then decreased, the points fitted on a second degree function with a significant correlation (p=0.01). It depicts, that the colour of powder became more red and darker as the colour agent content increased. The colour differences ΔE*abcalculated between samples with different colour agent content were smaller above 130 ASTA units. It shows that the rate of the change of the paprika powders colour was smaller while the colour agent content increased.

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.

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.

scholarly journals Influence of the Varnishing "Surface" Coverage on Optical Print Characteristics

2020 ◽  
Vol 14 (4) ◽  
pp. 428-433
Author(s):  
Tomislav Hudika ◽  
Igor Majnarić ◽  
Tomislav Cigula
Keyword(s):  
Surface Coverage ◽  
Colour Change ◽  
The Other ◽  
Colour Difference ◽  
Printing Process ◽  
Laboratory Environment ◽  
Uv Led ◽  
Cost Efficient ◽  
Colour Coordinates ◽  
Colour Appearance

Varnishing is often used to protect or decorate the print, but it can also influence the print’s colour appearance. Therefore, varnishing should enhance the print role, while colour change should be kept as low as possible. The aim of this paper is to evaluate inkjet UV LED varnishing by estimating optical print characteristics. Prepared offset prints were UV LED varnished in different surface coverage values (SCV) with a matte and gloss finish. The prints were evaluated by measuring gloss and colour coordinates. Secondly, varnishing was performed in a different SCV, which enabled assessing the optimal SCV, i.e. the most cost-efficient varnishing. The printing process was conducted in a standardized and controlled laboratory environment, regulated via the ISO 12647-2:2013 norm to ensure that the black colour was reproduced in the standard tolerance. The results showed that the colour difference is negligible (stays in the ISO tolerances), regardless of the varnishing SCV. On the other hand, the optimal printing gloss is at the SCV of 100%.

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