1、BRITISH STANDARD BS3900-D10: 1986 ISO7724-3: 1984 Methods of test for paints Part D10: Determination of colour and colour difference: calculation ISO title: Paints and varnishes Colorimetry Part3:Calculation of colour differences UDC 667.612:535.65BS3900-D10:1986 This British Standard, having been p
2、repared under the direction of the Pigments, Paints and Varnishes Standards Committee, was published under the authority of the Board of BSI and comesintoeffect on 31 October1986 BSI 07-1999 The Committees responsible for this British Standard are shown inBS 3900: Introduction The following BSI refe
3、rences relate to the work on this standard: Committee reference PVC/10 Draft for comment 82/56107 DC ISBN 0 580 15363 0 Amendments issued since publication Amd. No. Date of issue CommentsBS3900-D10:1986 BSI 07-1999 i Contents Page National foreword ii 0 Introduction 1 1 Scope and field of applicatio
4、n 1 2 References 1 3 Calculation 1 4 Test report 3 Publications referred to Inside back coverBS3900-D10:1986 ii BSI 07-1999 National foreword This Part of BS3900 has been prepared under the direction of the Pigments, Paints and Varnishes Standards Committee. It is identical with ISO7724-3:1984 “Pain
5、ts and varnishes Colorimetry Part3: Calculation of colour differences”. published by the International Organization for Standardization (ISO) with the active participation and approval of the United Kingdom. Terminology and conventions. The text of the international standard has been approved as sui
6、table for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to
7、use a full point on the baseline as the decimal marker. Wherever the words “International Standard” and “part of ISO7724” appear, referring to this standard, they should be read as “British Standard” and “Part of BS3900” respectively, and where the identification “ISO7724-3” appears, it should be re
8、ad as “BS3900-D10”. The Technical Committee has reviewed the relevant provisions of the CIE publications, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. These publications are published by Commission Internationale dclairag
9、e (CIE) and obtainable from the Hon. Librarian (National Illumination Committee), c/o Thorn Lighting Limited, Great Cambridge Road, Enfield, Middlesex EN11UL. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for the
10、ir correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standard Corresponding British Standard BS3900 Methods of test for paints ISO3668:1976 PartD1:1978 Visual comparison of the colour of paints (Identical
11、) ISO7724-1:1984 PartD8:1986 Determination of colour and colour difference: principles (Identical) ISO7724-2:1984 Part D9:1986 Determination of colour and colour difference: measurement (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1to4
12、, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS3900-D10:1986 BSI 07-1999 1 0 Introduction This International Standard, ISO7724, comprises t
13、he following parts: Part 1: Principles; Part 2: Colour measurement; Part 3: Calculation of colour differences. Parts1,2 and3 of ISO7724 describe methods for the instrumental determination of the colour co-ordinates and colour differences of paint films, as required for such purposes as a) the object
14、ive description of colour differences between a test specimen (a test panel coated with a paint, or a specimen from a painted article) and a reference specimen; b) determining colour deviations in the production of painted articles so that the results may be used for the control or regulation of the
15、 process; c) the objective description of changes in colour caused by weathering and other chemical or physical influences; d) the objective supervision of colour reference standards. NOTEColour reference standards are subject to ageing, which may lead in the course of time to pronounced changes in
16、colour. High accuracy colorimetry is required for the timely detection of these changes. This is of particular importance when ordering against such reference standards. 1 Scope and field of application This part of ISO7724 describes a method for the quantitative colorimetric evaluation of small col
17、our differences between paint films. NOTEThere are numerous formulae for calculating a colour differences from the colour co-ordinates of two specimens. For various reasons the results given by such formulae, including the one defined here, do not in all cases agree satisfactorily with visual percep
18、tion nor are they likely to agree with each other. The Commission Internationale de lEclairage (CIE) recommended in1976 two formulae for general use. One of these, the CIE1976 (L* a* b*) colour difference formula (see CIE Publication No. 15 SupplementNo.2), has proved to be of practical value for th
19、e colorimetric evaluation of paint films and is specified for this application in this part of ISO7724. 2 References ISO3668, Paints and varnishes Visual comparison of the colour of paints. ISO7724-1, Paints and varnishes Colorimetry Part1: Principles. ISO7724-2, Paints and varnishes Colorimetry Par
20、t2: Colour measurement. CIE Publication No.15, Supplement No. 2, Recommendations on uniform color spaces Color difference equations Psychometric color terms. CIE Publication No.38, Radiometric and photometric characteristics of materials and their measurements. 3 Calculation 3.1 General Calculate th
21、e differences in colour, lightness, chroma and hue between the paint films of a test specimen and a reference specimen from their colour co-ordinates in the CIE1976 (L* a* b*) colour space (seeISO7724-1). NOTEThe abbreviation CIELAB is used for CIE1976 (L* a* b*). Determinethe colour co-ordinates of
22、 the test specimen, and the colour co-ordinates of the reference specimen according to ISO7724-2 (see note1) by use of a measurement condition that depends on the information that is to be obtained: a) If the colour difference between the test specimen and the reference specimen, resulting only from
23、 the colour difference of the colouring material, is to be determined (for example when colour changes in pigments caused by weathering shall be objectively described) L*, a*, b* colour co-ordinates have to be calculated from the tristimulus values measured including specular reflection as described
24、 in subclause4.1.1 or 4.2.1 of ISO7724-2. L * T , a * T , b * T , L * R , a * R , b * R ,BS3900-D10:1986 2 BSI 07-1999 The measurements include the entire surface reflection. Therefore a mathematical correction of the measured tristimulus values X m , Y m , Z mis necessary to avoid the evaluation of
25、 colour differences that are too small because of the curve of the cube root functions f(X/X n ), f(Y/Y n ), f(Z/Z n ) used for the calculation of L*, a*, b*. The correction is made by use of the following equations: where X n , Y n , Z nare the tristimulus values for the perfect reflecting diffuser
26、 (see Table2 in ISO7724-1); A 0is the Fresnel reflectance (see CIE Publication No. 38) and is assumed to be0,04 based on a refractive index n = 1,5 (see note2) b) If the colour difference between the test specimen and the reference specimen, resulting from both the colour difference of the colouring
27、 material and the difference in the surface reflection, is to be determined (as they are perceived roughly when visually comparing the colour according to ISO3668) L*, a*, b* colour co-ordinates have to be determined excluding specular reflection, as described in subclause 4.1.2 or 4.2.2 of ISO7724-
28、2. If methods a) and b) are carried out, comparable results are obtained for high gloss paint films. In all other cases, the degree of comparability of the colour differences obtained using the two methods will be dependent on the gloss differences between the test specimens and the reference specim
29、ens and on the construction of the photometer head. NOTE 1With modern instruments it is not absolutely necessary to calculate the co-ordinates of the test specimens because the colour difference is calculated automatically from the reference values stored in the instrument. NOTE 2When the correction
30、 is made for very dark or highly chromatic paint films it may be appropriate to use a more precise value ofA 0 ; this should be started in the test report. The mathematical elimination of the surface reflection affects the correspondence of the colour differences thus obtained to those that are seen
31、 by an observer when examining highly reflecting test specimens with the exclusion of gloss. 3.2 Total colour difference using the CIELAB colour difference formula The total difference between two colours is the geometrical distance between their positions in the CIE1976 (L* a* b*) colour space (see
32、 ISO7724-1), and is calculated from the equation where 3.3 Lightness difference The lightness difference between the test specimen and the reference specimen is defined by the CIE1976 psychometric lightness difference 3.4 Chroma difference The chroma difference between the test specimen and the refe
33、rence specimen is defined by the CIE1976 ab chroma difference where is the CIE1976 a b chroma of the test specimen and is defined by the equation %E ab *BS3900-D10:1986 BSI 07-1999 3 is the CIE1976 a b chroma of the reference specimen and is defined by the equation 3.5 Hue difference The hue differe
34、nce between the test specimen and the reference specimen is defined by the CIE1976 a b hue difference where The differences in lightness, chroma and hue are defined such that the sum of their squares equals the square of the colour difference. 3.6 Colour difference of near white test specimens The c
35、olour difference of near white test specimen should be described by use of ,and the differencesandin place ofand . 4 Test report The test report shall contain at least the following information: a) the type and identification of the paint film tested and of the reference specimen; b) a reference to
36、this International Standard (ISO7724-3); c) a description or other identification of the method of preparing the test specimen and the reference specimen; d) the identification of the method a) or b) used (see3.1); e) the results of the test, expressed as the colour differenceand, if necessary, the
37、psychometric lightness difference, the CIE1976 a b chroma difference,and the CIE1976 a b hue difference, or the differencesandas appropriate; f) any deviation, by agreement or otherwise, from the procedures specified; g) the date of the test. C ab, R * %H ab * %E ab * %L * %a * %b * %C ab * %H ab *
38、%E ab * %L * %C ab * , %H ab * %a * %b * ,4 blankBS3900-D10:1986 BSI 07-1999 Publications referred to See national foreword.BS3900-D10: 1986 ISO7724-3: 1984 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishS
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