1、Graphic technology Measurement and calculation of spot colour tone valueBS ISO 20654:2017BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06 ISO 2017Graphic technology Measurement and calculation of spot colour tone valueTechnologie graphique Mesurage et calcul de la va
2、leur de tons des couleurs daccompagnementINTERNATIONAL STANDARDISO20654First edition2017-08Reference numberISO 20654:2017(E)National forewordThis British Standard is the UK implementation of ISO 20654:2017.The UK participation in its preparation was entrusted to Technical Committee PAI/43, Graphic t
3、echnology.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2017 Published by
4、BSI Standards Limited 2017ISBN 978 0 580 95170 1ICS 37.100.01Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 September 2017.Amendments/corrigenda issued since
5、 publicationDate Text affectedBRITISH STANDARDBS ISO 20654:2017 ISO 2017Graphic technology Measurement and calculation of spot colour tone valueTechnologie graphique Mesurage et calcul de la valeur de tons des couleurs daccompagnementINTERNATIONAL STANDARDISO20654First edition2017-08Reference number
6、ISO 20654:2017(E)BS ISO 20654:2017ISO 20654:2017(E)ii ISO 2017 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electroni
7、c or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Ge
8、neva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 20654:2017ISO 20654:2017(E)ii ISO 2017 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be rep
9、roduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the request
10、er.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgISO 20654:2017(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Requirements 24.1 Calculation of spot col
11、our tone value 24.2 Steps for obtaining SCTV from spectral reflectance measurements 34.3 Steps for obtaining SCTV from CIELAB measurements . 3Bibliography 5 ISO 2017 All rights reserved iiiContents PageBS ISO 20654:2017ISO 20654:2017(E)ForewordISO (the International Organization for Standardization)
12、 is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be repre
13、sented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to devel
14、op this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/
15、IEC Directives, Part 2 (see www .iso .org/ directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during
16、 the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the vol
17、untary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www .iso .org/ iso/ foreword .h
18、tml.This document was prepared by Technical Committee ISO/TC 130, Graphic technology.iv ISO 2017 All rights reservedBS ISO 20654:2017ISO 20654:2017(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work
19、of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-government
20、al, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the I
21、SO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).Attention is drawn to the possi
22、bility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of
23、 patent declarations received (see www .iso .org/ patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related
24、to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www .iso .org/ iso/ foreword .html.This document was prepared by Technical Committee ISO/TC 130, Graphic technology.i
25、v ISO 2017 All rights reserved ISO 20654:2017(E)IntroductionThis document defines a new metric Spot Colour Tone Value (SCTV) for the determination of the tone value of a spot colour ink. Spot colours in this document are defined as non-process colours (process colours being the CMYK 4-colour primary
26、 inks). This method produces approximately uniform visual spacing of the tones between the unprinted substrate and the 100% coverage, known as the solid ink. This metric is calculated from either the measured spectral reflectance factors or from colorimetric values computed from the same spectral da
27、ta.Historically, spot colours have been managed by measuring the solid ink value only, with no clear guidelines or methodology for measuring intermediate halftones. For artwork that only incorporates the spot ink at full coverage, this can be a reasonable practice; however, for artwork that includes
28、 gradations of the spot colour, which can print alone or in combination with the other inks, a formal strategy for managing the spot colour tone is required. This solution has been to print linear scales and use those values as a reference tone for alignment. This practice renders different results
29、from each print supplier.In the past, spot colour tones have been measured using the standard process colour tones methodology based on ISO status density measurement using a set of spectral products optimised for cyan, magenta and yellow inks. This method does not work well with intermediate tones
30、of spot colours and in many cases produced a tone scale far from being perceptually uniform. Hence, there is a need for a new metric that will quantify the intermediate tones of spot colours in a more perceptually uniform way.This document is the result of work done by many people in developing and
31、testing a range of candidate metrics. In particular, significant contributions were made by William B. Birkett, Charles Spontelli and Hanno Hoffstadt. ISO 2017 All rights reserved vBS ISO 20654:2017Graphic technology Measurement and calculation of spot colour tone value1 ScopeThis document defines a
32、 metric for assessing intermediate tones of a spot ink. This method for the calculation of Spot Colour Tone Value (SCTV) produces approximately uniform visual spacing of tones between substrate and solid. It can be calculated from spectral reflectance or colorimetric measurements of the solid ink, s
33、ubstrate and one or more patches of intermediate tones to be measured.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated
34、 references, the latest edition of the referenced document (including any amendments) applies.ISO 13655, Graphic technology Spectral measurement and colorimetric computation for graphic arts images3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.ISO
35、 and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp3.1colour exchange formatCxF/Xstandard defining a format for the
36、 communication of spot ink characterisation data (CxF/X-4)3.2spot colour inkink which is not part of the set of process inksNote 1 to entry: Spot colour inks are often used when printing brand colours.SOURCE: ISO 12647-7, 3.93.3Spot Colour Tone ValueSCTVvalue which describes the apparent halftone ar
37、ea for a non-process inkNote 1 to entry: The series of all possible tone values between the unprinted substrate and the fully covered, solid tone will produce an approximately uniform visual spacing of the colours of the printed tones. The range of this metric is 0 % to 100 %, where 0 represents sub
38、strate and 100 represents solid spot colour.INTERNATIONAL STANDARD ISO 20654:2017(E) ISO 2017 All rights reserved 1BS ISO 20654:2017Graphic technology Measurement and calculation of spot colour tone value1 ScopeThis document defines a metric for assessing intermediate tones of a spot ink. This metho
39、d for the calculation of Spot Colour Tone Value (SCTV) produces approximately uniform visual spacing of tones between substrate and solid. It can be calculated from spectral reflectance or colorimetric measurements of the solid ink, substrate and one or more patches of intermediate tones to be measu
40、red.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (includ
41、ing any amendments) applies.ISO 13655, Graphic technology Spectral measurement and colorimetric computation for graphic arts images3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.ISO and IEC maintain terminological databases for use in standardizat
42、ion at the following addresses: IEC Electropedia: available at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp3.1colour exchange formatCxF/Xstandard defining a format for the communication of spot ink characterisation data (CxF/X-4)3.2spot
43、colour inkink which is not part of the set of process inksNote 1 to entry: Spot colour inks are often used when printing brand colours.SOURCE: ISO 12647-7, 3.93.3Spot Colour Tone ValueSCTVvalue which describes the apparent halftone area for a non-process inkNote 1 to entry: The series of all possibl
44、e tone values between the unprinted substrate and the fully covered, solid tone will produce an approximately uniform visual spacing of the colours of the printed tones. The range of this metric is 0 % to 100 %, where 0 represents substrate and 100 represents solid spot colour.INTERNATIONAL STANDARD
45、 ISO 20654:2017(E) ISO 2017 All rights reserved 1 ISO 20654:2017(E)4 Requirements4.1 Calculation of spot colour tone valueThis subclause defines a formula for Spot Colour Tone Value (SCTV) that depends on standard colorimetric variables. Two sub-clauses then outline the steps for calculating SCTV fr
46、om spectral reflectance data and from CIELAB values.For back-lit materials, spectral transmittance should be used in place of spectral reflectance.NOTE The calculation of SCTV can be generalized to the measurement of regular transmittance or diffuse transmittance factor for use in the determination
47、of tone values of printed back-lit signs. The details of making such measurements are beyond the scope of this document.The SCTV of an intermediate tone of a spot ink is defined as a substrate-relative metric composed of three “value” components and normalized between substrate (0 %) and spot ink so
48、lid (100 %), as shown in Formula (1):SCTVxt xp yt yp zt zpxs xp ys y=()+()+()()+1002222VV VV VVVV VVppzszp()+()22VV(1)whereVxs, Vys, Vzsare Vx, Vy, Vzvalues calculated for the spot ink solid;Vxp, Vyp, Vzpare Vx, Vy, Vzvalues calculated for the substrate;Vxt, Vyt, Vztare Vx, Vy, Vzvalues calculated f
49、or the spot ink tone.The value components are defined to have functional form similar to that of CIE L*, as shown in Formulae (2)(6):VfXXx=n116 16 (2)VfYYy=n116 16 (3)VfZZz=n116 16 (4)whereX, Y, Z are tristimulus values calculated as specified in ISO 13655;Xn, Yn, Znare tristimulus values of the selected illuminant and observer, which will normally be D50 for graphic arts applications as specified in ISO 13655.and wherefu u()=()13if u 6293(5)fu u()=()+941108429if u
