15 – 17 June 2006, Ljubljana, Slovenia
DISADVANTAGESOF FLAGS COLOUR DEFINITION USING SUBJECTIVE EVALUATION SYSTEM
Đurđica PARAC OSTERMAN1,Martinia JOANELI1
1Faculty of Textile Technology
Abstract: The analyses in this paper were performed on the University of Zagreb flag, originally made from PES fabric, for which the legal regulation has been performed by the Faculty of Textile Technology. The primer evaluation has been performed according to Pantone, CMYK system and CIE objective evaluation system. The colour of the flag has been evaluated as the Pantone 19-3952 TPX. In CMYK system the values were 85, 70, 6 and 0. The spectrophotometric colour parameters values were: h* (hue) 285, C* (chroma) 40 and L* (lightness) 31. After this analyze, using colour match prediction operation, the reproduction of the original colour was performed on PA and CV materials. Comparing the original fabric colour with one on PA and CV materials, the dE values were higher than 1,5 for PA and higher of 2 for CV. As for the colour parameter difference, the most emphasized was hue parameter difference (dh*).
Keywords:colour appearance, subjective evaluation, CIE system, color matching
1.Introduction
According to Herring[1]the color constancy of objects perceived in every day life, retain in persons memory as the constant characteristic of the object. This theory is the interpretation of electromagnetic wave frequency in a visible part of the spectrum (360 – 740 nm)[2], [3]. The impression of strength of perceived colour depends also on its intensity or the size of coloured surface. Even than Goethe[4] established the differences in colour lightness which he defined by simple scale of numbered values from 0 to 10.
Nowadays, the colour science respect three basic theories of colour visualization[5],[6]; Young – Helmholtz trichromatic theory, Herrings theory of opposite colours and Lands retinal theory. In any case, the definition of colour is subjective and individual process, and the preciseness of systematic colour description is difficult to achieve. Numerous scientists together with the artists, through the history of colour science development, have therefore tried to solve the problem of colour description, including Nobel laureate W. Ostwald and the American artist A. H. Munsell, who studied the problem in great deal[7], [8],[9]. In such systems the colours can be classified in various verbal or numerical terms, which exclude the objective evaluation of colour.
The adoption of the original CIE system in 1931 was the most important single step in the development of Colour Science an colour objective evaluation. The CIE system defines colours as vectors in three dimensional space accepted as CIEL*a*b* space. An object colour can be uniquely defined by three numbers called tristimulus values (X, Y, Z), chromaticity co-ordinates (x, y, z) and dominate wavelength .
The colour of official state, city and club flags are precisely defined and are subjected to copyright. The K. L. Keily system for colour definition has been accepted. The system is based on Munsell colour order system which was also the base for Inter – SocietyColour Council (ISCC) and National Bureau of Standards – NBS. The system defines the colour on five levels, both on subjective and objective evaluation. Colour evaluation by means of colorimetric co-ordinates exclude any subjectivity and assures the constancy of colour[10].
2.EXPERIMENTAL
The analyses in this paper were performed on University of Zagreb blue shaded official flag which is produced of PES fabric, and also on PA and CV textile substrates dyed with disperse dyestuff in aim of reproducing the original colour of the flag.
The original colour evaluated according to PANTONE colour order system was defined as Pantone 19 – 3952 TPX.
Also the objective evaluation of original flag colour was performed by spectrophotometric measurement on remission spectrophotometer DataColor 600+CT, D65, d/8.
The measured values are presented in Table 1. as the dE values using the values for PES coloured substrate and the Pantone 19 – 3952 TPX values as the standard, and also on C*/Y graph (Figure 1.).
Visual evaluation (psychophysical analyse) of coloured samples has been performed on 30 candidates observers (age 21 – 40). The samples were evaluated under D65 illumination (Xenon lamp), on the distance of 60 cm. Samples were ranged according to evaluated C (chroma) and H (hue) values. Subjectively evaluated values were statistically analysed and were presented through the coefficient of variation value (V) as the definition of intensity (equation 1, figure 2.).
(1),
where σ is the standard deviation and the Xis the mean of samples.
3.RESULTS AND DISCUSSION
The common approach to official flag colour evaluation is by means of CMYK, RAL, PANTONE and RGB values. Nevertheless, since 2000. most of the countries accepting the official flag colour evaluation through CIELAB numerical system, while system such PANTONE particularly are excluded due to the lack of preciseness of subjective evaluation performed by such system. Subjective evaluation is influenced by numerous parameters among the most important is the influence of the observer visualisation.
In Table 1, the colouristic values of University of Zagreb official flag are presented. Also the colouristic values of PA and CV dyed textile samples were presented and compared to the original and also to the values according to Pantone 19 – 3952 TPX.
Table 1:Colouristic values of original flag and colour reproduced on PA and CV samples, and dE values
Samples / L* / C* / H* / dE (original PES) / dE (PANTONE)Original PES / 30 / 40 / 285 / - / 5,9
Dyed PA / 31 / 38 / 283 / 2,2 / 4,4
Dyed CV / 30 / 42 / 287 / 3 / 8,6
PANTONE sample / 34 / 35 / 284 / 5,9 / -
According to the results shown in Table 1., it can be seen that the most significant differences is in hue parameter regarding the Pantone values. dE values obtained are higher than 4,5 also regarding Pantone 19-3952 TPX evaluation. Differences obtained regarding PES textile substrate are obtained due to the differences in textile fabric affinity.
Results of differences obtained higher for Pantone, showed in table 1., and on figure 1., confirm the unreliability of evaluation performed through PANTONE etalons.
Figure 1:C*/Y relation.
On Figure 2, the relationship of PANTONE evaluation versus observer experience intensity evaluated through coefficient of variation value (%) is presented. Results were obtained using values for Pantone 19-3952 TPX as the standard. Samples are ranged regarding the experienced intensity of chroma C and hue H.
Figure 2:Relationship of PANTONE evaluation versus observer experience intensity
It is confirmed that the experience of hue parameter depends on the surface on which the colour is presented. Results showed that the intensity of subjective observer experience regarding the etalon Pantone 19-3952 TPX is the most emphasized for hue value.
All this results confirmed the unsuitability and the unreliability of colour evaluation Through PANTONE or RAL colour system due to the problem of objectivity and no precise range in colour classification.
4.CONCLUSION
Colour of state, city or clubs official flags are precisely defined and are subjected to copyright. The interpretation of official flag original colour must be consistent regardless the surface.
In this paper the necessity of objective, numerical colour evaluation through CIE system is confirmed due to its reliability and preciseness in evaluation. Such system are nowadays accepted as the only suitable systems for colour evaluation.
Also, the CIE system acquire the possibility of data conversion to CMYK values which is essential for graphic operations.
It is important to point out that the colour evaluation by means of PANTONE and RAL colour order systems cannot assure the precise and objective colour definition due to its dependence on subjective colour perception of an observer.
The influence of the textile substrate is also significant due to its influence on colour hue reproduction.
5.REFERENCES
[1]CROZIER, w., r.: The Psychology of Colour Preferences, Re. Prog. Coloration, Vol.26, (1996.),pp. 63
[2]CLULOW, f., w.:Colour and its Principles, Fountain PressLondon, London, (1972)
[3]Macdonald, L.: Colour in Visual Dislpays, JSDC, Vol. 112, (1996.), pp. 2
[4]GUILD, J.: The Colorimetric Properties of the Spectrum, Phl. Trans. Roy. Soc., London, (1931.)
[5]MacLAREN, K.: Colour Space, Colour Physic for Industries, Eds R. MacDonald SDC, Yorkshir, (1987).
[6]MUNSELL, A., H.: A Grammar of COLOUR, Van – Nosttand Reinhold, New York, (1969.)
[7]NICKERSON, D.: History of MunsellColour System, Colour Research Application, Vol. 4, (1976.), pp. 23
[8]PATTERSON, D.: The Development of Colour Science, Rev. Prog. Coloration, Vol. 7, (1976.), pp. 63
[9]RUE, R.: Colour Appearance Assessment, JSDC, Vol. 112, (1996.), pp. 72
[10]WYSZECKI, W.; STILES, W., S.: Colour Science – Concept and Methods, Quantitative Data and Formulae, Edt. John Wiley & Sons Ltd., England, ISBN 0 – 471 – 02106 – 7
6.ADITIONAL DATA ABOUT Authors
1. Đurđica Parac - Osterman, dr. sc. prof., Faculty of Textile Technology, University of Zagreb, Baruna Filipovića 30, , +385 1 48 77 359, +385 1 48 77 355
2. Martinia Joaneli, mr. sc. assistant, Faculty of Textile Technology, University of Zagreb, Baruna Filipovića 30, , +385 1 48 77 365, +385 1 48 77 355
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