1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 17321-1:2012Graphic technology andphotography Colourcharacterisation of digital stillcameras (DSCs)Part 1: Stimuli, metrology and testproceduresBS ISO 17321-1:2012 BRITISH
2、 STANDARDNational forewordThis British Standard is the UK implementation of ISO 17321-1:2012.It supersedes BS ISO 17321-1:2006 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee CPW/42, Photography.A list of organizations represented on this committee can
3、beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012 ISBN 978 0 580 71332 3 ICS 37.040.10 Complia
4、nce with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 November 2012. Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 17321-1:2012 ISO 2012Graphic techn
5、ology and photography Colour characterisation of digital still cameras (DSCs) Part 1: Stimuli, metrology and test proceduresTechnologie graphique et photographie Caractrisation de la couleur des appareils photonumriques Partie 1: Stimuli, mtrologie et modes opratoires dessaiINTERNATIONAL STANDARDISO
6、17321-1Second edition2012-11-01Reference numberISO 17321-1:2012(E)BS ISO 17321-1:2012ISO 17321-1:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any
7、 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 requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyri
8、ghtiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 17321-1:2012ISO 17321-1:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 DSC colour characterization methods 24.1 General . 24.2 Spectral sensitivity-b
9、ased characterization Method A 34.3 Target-based characterization Method B 4Annex A (informative) Recommended laboratory set-up for photographing a reflection colour test target . 8Annex B (informative) Digital still camera/sensitivity metamerism index (DSC/SMI)10Annex C (informative) Characterizati
10、on target considerations 16Annex D (informative) Calculating natural scene element responses from spectral characterization data 23Bibliography .26BS ISO 17321-1:2012ISO 17321-1:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bo
11、dies (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 committee. International organizatio
12、ns, 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 accordance with the rules given in the I
13、SO/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 requires approval by at least 75 % of the
14、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 17321-1 was prepared by Technical Committee ISO/TC 42, Photography, i
15、n collaboration with ISO/TC 130, Graphic technology.This second edition cancels and replaces the first edition (ISO 17321-1:2006), of which it constitutes a minor revision with the following changes: in 4.3.3.4.2, the typographical error “senor image area” was corrected to “sensor image area”; in B.
16、2.6, a broken link to tools for non-linear optimization has been updated.ISO 17321 consists of the following parts, under the general title Graphic technology and photography Colour characterization of digital still cameras (DSCs): Part 1: Stimuli, metrology and test procedures Part 2: Consideration
17、s for determining scene analysis transforms Technical Reportiv ISO 2012 All rights reservedBS ISO 17321-1:2012ISO 17321-1:2012(E)IntroductionThe spectral responses of the colour analysis channels of digital still cameras (DSCs) do not, in general, match those of a typical human observer, such as def
18、ined by the CIE standard colorimetric observer. Nor do the responses of different DSCs ordinarily match each other. In characterizing DSCs, it is therefore necessary to take account of the DSC spectral sensitivities, illumination, and encoding colour space. This part of ISO 17321 will begin to addre
19、ss these considerations. This part of ISO 17321 defines stimuli (spectral illumination or a colour target), metrology and photographic test procedures for acquiring DSC characterization data. It specifies test procedures for “scenes”, the most general picture taking conditions where metameric colour
20、s and a range of illumination sources are encountered. It also specifies test procedures for hardcopy “originals”, a more narrowly defined picture-taking condition in which the illumination source and the colorants being imaged are pre-defined.ISO 17321 will distinguish among several possible image
21、representations in different colour encodings as depicted in Figure 1 which shows the diagram of a generic image workflow for digital photography.Figure 1 Generic image workflow for digital photographyThe DSC characterizations obtained using this part of ISO 17321 will be applicable to raw (sensor-r
22、eferred) DSC data. Two alternative methods are described for obtaining these characterization data. Method A, the spectral method, uses spectral lights as stimuli for measuring the colour performance of a DSC. Method B, the target method, involves the use of a physical colour test target under speci
23、fic lighting conditions to measure DSC colour performance. Annexes A to C recommend a laboratory set-up for photographing reflection targets, provide target patch selection criteria, and provide a digital still camera metamerism index. ISO 2012 All rights reserved vBS ISO 17321-1:2012ISO 17321-1:201
24、2(E)Some operations (colour pixel reconstruction, flare removal, white balancing) can be performed without disqualifying the DSC data as being raw. However, operations that render the image data so that they become output-referred (ready to display or to print) generally do disqualify the data. With
25、 such cameras, this standard can only be applied if the capability exists to extract or to regenerate raw data, e.g. by applying the inverse of the rendering transform or by tapping the appropriate signals internal to the camera.The technical experts who have developed this part of ISO 17321 recogni
26、ze that a standard that could be applied generally to any (not just raw) DSC output would be desirable. Such a standard is problematic for DSCs that employ colour-rendering algorithms in order to produce output-referred image data. For such DSCs, it would frequently be impossible to determine if col
27、our analysis errors relative to the scene or original captured were due to sensor image encoding errors or to proprietary colour rendering algorithms. The only way to make this distinction is if the colour rendering used is well documented and available, and the rendered data can be converted to un-
28、rendered data by inverting the colour rendering. This situation is unlikely to occur because one of the major differentiators in DSC performance is the colour rendering. Sophisticated colour-rendering algorithms can be image dependent, and locally varying within an image. This makes it extremely dif
29、ficult to reliably determine the exact colour rendering used by analysing captured test scenes.The purpose of this part of ISO 17321 is both to assist in the characterization of DSCs for colour management purposes and to assist camera manufacturers in the determination of the colour analysis capabil
30、ities of DSCs that they are developing. This standard is applicable to any DSC intended for photographic or graphic technology applications. However, for many users it is not practical to apply this part of ISO 17321 to individual DSCs. Some of the measurements described in this part of ISO 17321 re
31、quire complex, expensive measurement equipment. In the case of test targets that are commercially produced, spectral as well as colorimetric measurement data would ideally accompany the target.Those unfamiliar with this part of ISO 17321 are encouraged to read through the entire standard (in particu
32、lar the informative annexes) before proceeding with DSC characterization, in order to verify appropriateness for their particular application. In some cases, the procedures described in the multimedia standard, IEC 61966-95might be more applicable.It is proposed that other parts of ISO 17321 will be
33、 developed in the future to deal with other aspects of the colour characterization of digital still cameras.vi ISO 2012 All rights reservedBS ISO 17321-1:2012INTERNATIONAL STANDARD ISO 17321-1:2012(E)Graphic technology and photography Colour characterisation of digital still cameras (DSCs) Part 1: S
34、timuli, metrology and test procedures1 ScopeThis part of ISO 17321 specifies colour stimuli, metrology, and test procedures for the colour characterization of a digital still camera (DSC) to be used for photography and graphic technology. Two methods are provided, one using narrow spectral band illu
35、mination and the other using a spectrally and colorimetrically calibrated target. Except for a specific set of permitted data operations, these DSC data are raw.This part of ISO 17321 does not specify the methods for deriving transformations from raw DSC data in order to estimate scene colorimetry.2
36、 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 7589, Photography Illumin
37、ants for sensitometry Specifications for daylight, incandescenttungsten and printerISO 13655, Graphic technology Spectral measurement and colorimetric computation for graphic arts imagesISO 14524:2009, Photography Electronic still-picture cameras Methods for measuring opto-electronic conversion func
38、tions (OECFs)3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1adopted whitespectral radiance distribution as seen by an image capture or measurement device and converted to colour signals that are considered to be perfectly achromatic and to have
39、 an observer adaptive luminance factor of unity; i.e. colour signals that are considered to correspond to a perfect white diffuserISO 22028-1NOTE 1 The adopted white can vary within a scene.NOTE 2 No assumptions can be made concerning the relation between the adapted or adopted white and measurement
40、s of near perfectly reflecting diffusers in a scene, because measurements of such diffusers will depend on the illumination and viewing geometry, and other elements in the scene that can affect perception. ISO 2012 All rights reserved 1BS ISO 17321-1:2012ISO 17321-1:2012(E)3.2digital still cameraDSC
41、device that incorporates an image sensor and that produces a digital signal representing a still pictureNOTE A digital still camera is typically a portable, hand-held device. The digital signal is usually recorded on a removable memory, such as a solid-state memory card or magnetic disk.3.3opto-elec
42、tronic conversion functionOECFrelationship between log of input levels and corresponding digital output levels for an opto-electronic digital image capture systemNOTE If the input log exposure points are very finely spaced and the output noise is small compared to the quantization interval, the OECF
43、 possibly has a step-like character. Such behaviour is an artefact of the quantization process and needs to be removed by using an appropriate smoothing algorithm or by fitting a smooth curve to the data.3.4raw DSC image dataimage data produced by, or internal to, a DSC that has not been processed,
44、except for A/D conversion and the following optional steps: linearization, dark current/frame subtraction, shading and sensitivity (flat field) correction, flare removal, white balancing (e.g. so the adopted white produces equal RGB values or no chrominance), missing colour pixel reconstruction (wit
45、hout colour transformations)3.5spectrally non-selectiveexhibiting reflective or transmissive characteristics that are constant over the wavelength range of interest4 DSC colour characterization methods4.1 GeneralTwo methods are specified for obtaining raw DSC colour characterization data, a spectral
46、 method and a target method. The method that is most applicable in any particular situation depends on a variety of factors including, but not limited to, the following: the extent of ones prior knowledge about the spectral content of the scenes or originals to be captured; the equipment available;
47、the accuracy required.The spectral method requires elaborate equipment in a laboratory environment, but can be used to produce characterization data for samples with arbitrary spectral distributions. The target method is suitable for studio and field use, but can only provide accurate characterizati
48、on data to the extent that the target spectral characteristics match those of the scene or original to be photographed.2 ISO 2012 All rights reservedBS ISO 17321-1:2012ISO 17321-1:2012(E)4.2 Spectral sensitivity-based characterization Method A4.2.1 Equipment4.2.1.1 GeneralSpectral sensitivity-based
49、characterization measurements shall be obtained by using a light source and monochromator to evenly illuminate a diffuse transmissive or reflective surface with electromagnetic radiation (light) containing a limited range of wavelengths centred on selected wavelengths, as specified in 4.2.3. Integrated relative radiance measurements of the illuminated surface shall be obtained for each selected wavelength using a radiance or irradiance meter with a spectral sensitivity calibration accurate to within 0,1 %
