1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 12642-1:2011Graphic technology Inputdata for characterization offour-colour process printingPart 1: Initial data setBS ISO 12642-1:2011 BRITISH STANDARDNational forewordTh
2、is British Standard is the UK implementation of ISO 12642-1:2011.It supersedes BS ISO 12642:1996 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PAI/43, Graphic technology.A list of organizations represented on this committee can beobtained on request t
3、o its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 73109 9ICS 35.240.30; 37.100.99Compliance with a British Standard cannot confer immunity fromlegal obligations.This British
4、 Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2011.Amendments issued since publicationDate Text affectedBS ISO 12642-1:2011Reference numberISO 12642-1:2011(E)ISO 2011INTERNATIONAL STANDARD ISO12642-1Second edition2011-07-15Graphic technology Inp
5、ut data for characterization of four-colour process printing Part 1: Initial data set Technologie graphique Donnes dentre pour caractrisation dimpression en quadrichromie Partie 1: Ensemble de donnes initiales BS ISO 12642-1:2011ISO 12642-1:2011(E) COPYRIGHT PROTECTED DOCUMENT ISO 2011 All rights re
6、served. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requ
7、ester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2011 All rights reservedBS ISO 12642-1:2011ISO 12642-1:2011(E) ISO 2011 All rights reserved iiiContents Page Foreword iv
8、Introduction.v 1 Scope1 2 Normative references1 3 Terms and definitions .1 4 Requirements.2 Annex A (informative) Application notes9 Bibliography13 BS ISO 12642-1:2011ISO 12642-1:2011(E) iv ISO 2011 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide f
9、ederation 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 represented on that co
10、mmittee. 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. International Standards are drafted in accor
11、dance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requir
12、es approval by at least 75 % of the member bodies casting a vote. 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. ISO 12642-1 was prepared by Technic
13、al Committee ISO/TC 130, Graphic technology. This second edition cancels and replaces the first edition (ISO 12642-1:1996) and its Technical Corrigendum (ISO 12642-1:1996/Cor.1:2005) and introduces no change in the technical requirements. Subclause 4.4 and Annex B have been replaced by references to
14、 ISO 28178 which has been created to include the data exchange file format for this and other International Standards. ISO 12642 consists of the following parts, under the general title Graphic technology Input data for characterization of four-colour process printing: Part 1: Initial data set Part
15、2: Expanded data set BS ISO 12642-1:2011ISO 12642-1:2011(E) ISO 2011 All rights reserved vIntroduction 0.1 General background The technical content of this part of ISO 12642 is identical to ANSI IT8.7/3-1993. The ANSI document resulted from the joint efforts of an international industry group that i
16、ncluded participants representing a broad range of prepress vendors, film manufacturers, and users. This group, initially identified as the DDES (Digital Data Exchange Standards) Committee, later became the founders of the ANSI IT8 (Image Technology) accredited standards committee which is responsib
17、le for electronic data exchange standards in graphic arts prepress. In an environment in which colour information is passed between electronic publishing systems, it is essential for colour to be defined in an unambiguous manner. Substantial experimental evidence enables us to conclude that, for fov
18、eal vision, this can be achieved by specifying the mixture of three linearly independent stimuli required to match that colour. In 1931 a complete system of colour definition was developed by the CIE (Commission Internationale de lEclairage) based on experimental evidence published during the previo
19、us decade. This evidence confirmed the similarity between observers in making such a match. That system and its derivatives are now universally accepted for colour specification. Many half-tone colour printing processes, however, require more than three colourants. There are two reasons for this. Ge
20、nerally the gamut of colours achievable with three printing inks is rather limited, and printing additional inks can extend the gamut significantly. Furthermore, the provision of extra inks can reduce the magnitude of the visual change caused by the variability in colour and register which arises in
21、 print production. By far the most common additional ink used is black, and four-colour process printing is accepted as the norm for most forms of printing. The addition of an extra ink means that the production of a colour cannot, in general, be defined uniquely. As a result, different parts of a p
22、rinted sheet can use varying ink combinations to achieve the same colour. For many practical purposes it is desirable to specify this combination directly, rather than encode it by rules, and this leads to the requirement to transfer data in a four-colour, device-specific mode. If the same data are
23、to be used for other applications, or even if it needs to be modified for a different set of printing characteristics, some additional information is necessary to enable the receiver of the data to interpret it. This part of ISO 12642 has been developed to achieve this objective. It provides a data
24、set which can be transmitted with an image to enable the receiver, if required, either to transform the data into a device-independent state or correct it for a different printing characteristic. An alternative application of the tools provided by this part of ISO 12642 is to enable the characteriza
25、tion of output systems; in this context, work has been undertaken by the committee to generate data for the major types of half-tone printing processes which have been specified internationally. This procedure is described in the application notes (Annex A) and the data will be published in future a
26、nnexes. The body of this part of ISO 12642 defines the ink values to be used for characterizing any four-colour (cyan, magenta, yellow, and black) half-tone printing process (including gravure). These ink values are defined as either digital data in a computer or half-tone tone values on film. This
27、requires that particular care be taken in the preparation of film to ensure that the output device is properly “linearized” and the half-tone film values match the numerical data in the computer file. For some applications the film values used for linearization can be one or more generations removed
28、 from the film produced by the film writer. The measurement procedures and the data format to be used in determining and reporting tristimulus values (X,Y,Z) are also included. While the technique employed in this part of ISO 12642 applies to all output processes, the data have been optimized for fo
29、ur-colour half-tone printing. For non-half-tone processes, or those which use colourants that are significantly different from typical printing inks, it is advisable that the reference data file be determined in such a way that it provides reasonably uniform colour differences when the data file is
30、rendered. For a system which does not meet the criterion, the user-optional data set can be utilized. Suggestions for this are made in the application notes; however, they are not part of this part of ISO 12642. BS ISO 12642-1:2011ISO 12642-1:2011(E) vi ISO 2011 All rights reservedNote that this par
31、t of ISO 12642 does not define the physical layout of the patches or their size. This is because any such decision depends on the printing device to be used, and the area required for colour measurement. It is anticipated that a specific layout will be produced to suit the needs of the user. However
32、, in order to realize the colours necessary for the measurements of specific printing processes to be included as future annexes, it was necessary to produce a specific layout. This layout, composed of four groups of patches, has been adopted by both ANSI/CGATS and ISO/TC 130. Within TC 130 the digi
33、tal data in the appropriate format are contained in images S7 to S10 of the Standard Colour Image Data (SCID), ISO 12640-1:1997. For the guidance of others, this layout is shown in Figure A.1. 0.2 Technical background 0.2.1 Printing characteristics Various efforts have been made over the past 20 yea
34、rs to reduce the variation which occurs between printing presses. Initially, standards such as ISO 2846 were developed to specify the colour of printing inks. Subsequently, as a result of the lead of FOGRA/BVD in Germany, significant effort has been made in developing specifications which define con
35、straints for the ink transfer onto paper. This is achieved by specifying either the reflection density or the tristimulus values of a uniform (solid) printed ink film, and by specifying tolerances on the optical density (i.e. dot value) of various half-tone dot values. Within the international print
36、ing community such specifications are widely recognized and have become, in many cases, de facto printing standards. For magazine and periodical printing, SWOP (in the USA) and FIPP (in Europe) are widely recognized standards. For commercial printing, the specifications of FOGRA and PIRA are widely
37、known in Europe. Specifications are also evolving for newspaper and heat-set web production. Future annexes to this part of ISO 12642 might contain the colorimetric tristimulus values corresponding to these percent dot values when printed in accordance with a number of such printing specifications.
38、Such data can be used as the basis for the conversion between ink values and tristimulus values. Note that any characterization of the process takes account of all steps involved in print production. Thus it includes production of the separations, any contacting operations that might be required and
39、 platemaking. All of the printing specifications as referred to above include recommendations for maintaining consistency of such operations to ensure that validity of a characterization is maintained. For characterizing printing conditions which differ from the published specifications, two options
40、 exist. Either the large palette of colours can be printed and measured, or the process can be modelled analytically. The analytical modelling approach has the advantage of requiring far fewer colour measurements; the disadvantages lie in the accuracy of prediction. For many applications, a satisfac
41、tory compromise is achieved by using modelling for the modification of published data. This is discussed in more detail in the application notes. 0.2.2 Choice of colour palette It is generally agreed that measurement of a reasonably large number of colours is preferred for accurate characterization
42、of any printing process. It is not possible to be precise about how many colours are required; the number will depend on many factors including the accuracy of colour rendition required, the uniformity of spacing of the samples in terms of colour, the type of modelling process used, and any nonlinea
43、r characteristics of a specific printing process. However, practical experience suggests that measuring all combinations of six levels each for cyan, magenta, yellow, and black, preferably weighted towards lower half-tone dot values, will frequently prove adequate. Generally, for higher levels of bl
44、ack, the number of samples can be considerably reduced, since the colour difference between samples is very small. With the addition of single colour scales which contain extra values to assist in defining local nonlinearity, the accuracy obtained for most printing processes is adequate. A reduced-s
45、ize data set can be used if: a less accurate characterization is adequate; the process can be modelled accurately by one of the well-known models listed in the application notes; the aim of the measurement is to seek small corrections to an already accurate characterization. BS ISO 12642-1:2011ISO 1
46、2642-1:2011(E) ISO 2011 All rights reserved viiThe advantages of this approach are that the measurement effort is substantially lower and that the file size of the data is greatly reduced. This can be advantageous when images are compressed although, in general, even the larger file is small compare
47、d to most images. The proposal accepted for this part of ISO 12642 defines a colour palette consisting of 928 combinations of cyan, magenta, yellow, and black ink values. It is this palette (hereafter called the extended ink value data set) which has been measured to provide colour characterization
48、data on the major printing specifications. Where such an extensive set of data is not required, a subset of this palette which consists of 182 colours (hereafter called the basic ink value data set) is specified. It provides data suited to a variety of modelling methods and generally provides excess
49、ive data for any specific method. It is sufficient for almost all published modelling methods. For a characterization which cannot be achieved with the data sets defined in this part of ISO 12642, provision is made for a user-optional set of any size. The format of the data is defined in this part of ISO 12642. It is anticipated that the basic data set will be the default file supplied in the header of image files to be exchanged, and that by prior agreement, one of the larger palettes can be provided when required. It is the inten
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