1、Graphic technology and photography Colour characterization of digital still cameras (DSCs) Part 4: Programmable light emission system PD ISO/TS 17321-4:2016 BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06National foreword This Published Document is the UK implement
2、ation of ISO/TS 17321-4:2016. The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photography. 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
3、 of a contract. Users are responsible for its correct application. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 90199 7 ICS 37.040.10 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was publis
4、hed under the authority of the Standards Policy and Strategy Committee on 30 June 2016. Amendments/corrigenda issued since publication Date Text affected PUBLISHED DOCUMENT PD ISO/TS 17321-4:2016 ISO 2016 Graphic technology and photography Colour characterization of digital still cameras (DSCs) Part
5、 4: Programmable light emission system Technologie graphique et photographie Caractrisation de la couleur des appareils photonumriques Partie 4: Systme dmission de lumire programmable TECHNICAL SPECIFICATION ISO/TS 17321-4 Reference number ISO/TS 17321-4:2016(E) First edition 2016-06-01 PD ISO/TS 17
6、321-4:2016 ISO/TS 17321-4:2016(E)ii ISO 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical,
7、 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 office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzer
8、land Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org PD ISO/TS 17321-4:2016 ISO/TS 17321-4:2016(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Requirements 2 4.1 General . 2 4.2 Hardware requirements . . 3 4.2.1 General 3 4.2.
9、2 Operating condition 4 4.2.3 Specifications of the system . 4 4.2.4 Time stability and long-term stability of light intensity 7 4.3 Figure of merit for a colour target using a programmable light emission system . 9 4.3.1 General 9 4.3.2 Terms and notations of S R29 4.3.3 Method for the calculation
10、of S R210 4.3.4 Figure of merit 11 4.4 Report 11 Annex A (informative) Integrating sphere method and LED-driving method 13 Annex B (informative) Spectral power distribution optimization procedure for multiple LEDs.15 Annex C (informative) The need for constraints on the average values and maximum va
11、lues of S R2and CIEDE2000 .19 Annex D (informative) Evaluation method for light source generated by a programmable light emission system .21 Annex E (informative) S R2and CIEDE2000 recommendations for colorimetric image capture .24 Annex F (normative) S R2Land S R2calculation methods for a light emi
12、ssion system in which spectral distribution is only obtained by measurements .26 Bibliography .28 ISO 2016 All rights reserved iii Contents Page PD ISO/TS 17321-4:2016 ISO/TS 17321-4:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national stand
13、ards 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 committee. International orga
14、nizations, 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 develop this document and those intended for its
15、 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/IEC Directives, Part 2 (see www.iso.org/dir
16、ectives). 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 the development of the document will be in t
17、he 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 meaning of ISO specific terms and expressions rel
18、ated to conformit y 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. The committee responsible for this document is ISO/TC 42, Photography. ISO 17321
19、 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: Considerations for determining scene analysis transforms Technical Report Part 4: Programmable
20、light emission system Technical Specification The following parts are under preparation: Part 3: User controls and readouts for scene-referred imaging applications Technical Reportiv ISO 2016 All rights reserved PD ISO/TS 17321-4:2016 ISO/TS 17321-4:2016(E) Introduction There are many application ar
21、eas such as medical imaging, cosmetics, e-commerce, sales catalogue, fine art reproduction and artistic archive where colorimetric image capture and colorimetric image reproduction are desired. A high colour-fidelity imaging system using a black-and-white digital camera with rotary colour filters 12
22、 , and digital video cameras specified for colorimetric image capture 13 , both of which have the same colour sensitivity as the colour matching functions defined by CIE 1931, are available today and fulfil these requirements. However, Reference 12 is a large-scale device which cannot be used to cap
23、ture moving objects, and Reference 13 is dedicated to motion picture use. Digital still cameras (DSCs) are often used as convenient devices for colorimetric image capture. Typically, DSCs do not have sensor sensitivities that are linear transforms of the colour matching functions defined by CIE 1931
24、. It is, therefore, necessary that a matrix conversion from DSC-image- capture data to scene-colorimetric data be done to transform camera image data to estimates of scene colorimetric data. Although there are several methods to derive such a matrix, a method using colour targets is the most common
25、when there is no data describing the DSC sensor spectral sensitivities. Colour targets used to derive this conversion matrix are X-Rite ColorChecker Classic 1) , X-Rite ColorChecker Digital SG 2)and others. These targets are reflective and so have a limited colour gamut compared to scenes where the
26、subject includes highly saturated colours. In such a case, colour targets with highly saturated colours that can be used to derive the colour conversion matrix are very useful. This part of ISO 17321 is applicable to light emitting devices such as inorganic or organic LEDs, quantum dots and laser di
27、odes. Note that although an integrating sphere is typically used, other mechanisms would also be applicable. A procedure using a nonlinear Generalized Reduced Gradient (GRG) algorithm is specified in this part of ISO 17321 to minimize the square of the difference between a desired colour spectrum an
28、d the colour spectrum of the programmable light emission system. This part of ISO 17321 will make use of a metric (S R2 ), which provides a simple and direct means to calculate the colour difference between two spectra. This criterion (S R2 ) will be used as a method to evaluate the performance of a
29、 programmable light emission system in terms of its ability to match a reference spectral power distribution. S R2and CIEDE2000 metrics are both used for colour target evaluation. This programmable light emission system can generate arbitrary illuminants such as D55, D65 and Illuminant A. Annex D de
30、scribes evaluation metrics for light sources. This system has several advantages as follows. An arbitrary smooth spectral power distribution similar to colour targets under a light source can be produced. Many colour metamers can be generated easily. Colours with different luminance, same hue and sa
31、me saturation can be generated easily. Colours with different saturation, same luminance and same hue can be generated easily. Colours with high luminance can be produced. Reference colour target can be provided for display systems. 1) ColorChecker Classic is an example of a suitable product availab
32、le commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of this product. 2) ColorChecker Digital SG is an example of a suitable product available commercially. This information is given for the convenience of users of thi
33、s document and does not constitute an endorsement by ISO of this product. ISO 2016 All rights reserved v PD ISO/TS 17321-4:2016 Graphic technology and photography Colour characterization of digital still cameras (DSCs) Part 4: Programmable light emission system 1 Scope This part of ISO 17321 specifi
34、es requirements for a programmable light emission system to produce various spectral radiance distributions intended for DSC colour characterization applications. NOTE 1 Evaluation metrics are described in this part of ISO 17321. These evaluations metrics are intended to provide “Figure of Merit (go
35、odness)” relating to the ability of the device to produce arbitrary spectral power distributions. NOTE 2 This part of ISO 17321 applies to a programmable light emission system composed of LEDs. However, it can be applied to light emitting devices such as quantum dots, organic LEDs, laser diodes and
36、so forth. NOTE 3 If spiky spectral reproduction is required, devices which have more spiky spectral light emission are intended to be used. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For
37、dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 7589, Photography Illuminants for sensitometry Specifications for daylight, incandescent tungsten and printer 3 T erms a nd definiti ons For
38、 the purposes of this document, the following terms and definitions apply. 3.1 colour matching functions tristimulus values (3.6) of monochromatic stimuli of equal radiant power SOURCE: CIE Publication 17.4, 845-03-23 3.2 colour rendering index R measure of the degree to which the psychophysical col
39、our of an object illuminated by a test illuminant conforms to that of the same object illuminated by the reference illuminant, suitable allowance having been made for the state of chromatic adaptation SOURCE: CIE Publication No. 17.4:1987, 845-02-61 TECHNICAL SPECIFICATION ISO/TS 17321-4:2016(E) ISO
40、 2016 All rights reserved 1 PD ISO/TS 17321-4:2016 ISO/TS 17321-4:2016(E) 3.3 digital still camera DSC device which incorporates an image sensor and which produces a digital signal representing a still picture Note 1 to entry: A digital still camera is typically a portable, hand-held device. The dig
41、ital signal is usually recorded on a removable memory, such as a solid-state memory card or magnetic disk. SOURCE: ISO 17321-1:2012, 3.2 3.4 light-emitting diode LED semiconductor diode that emits non coherent optical radiation through stimulated emission resulting from the recombination electrons a
42、nd photons, when excited by an electric current SOURCE: IEC 60050-521, 521-04-39 3.5 raw DSC image data image data produced by or internal to a DSC that has not been processed, except for A/D conversion and the following optional steps: linearization, dark current/frame subtraction, shading and sens
43、itivity (flat field) correction, flare removal, white balancing (e.g. so the adopted white produces equal RGB values or no chrominance), missing colour pixel reconstruction (without colour transformations). SOURCE: ISO 17321-1:2012:3.4 modified. 3.6 tristimulus values amount of the three reference c
44、olour stimuli, in a given trichromatic system, required to match the colour of the stimulus considered Note 1 to entry: See colour matching functions (3.1). SOURCE: CIE Publication 17.4, 845-03-22 4 Requirements 4.1 General Figure 1 shows a section of an integrating sphere. This sphere is one method
45、 to ensure good spatial uniformity. Light emitting devices are placed at the bottom and an output window is placed on the side to allow the mixed light to be emitted. Annex A shows a typical LED-driving method. NOTE 1 Integrating sphere is a typical case, but other mechanisms would be applicable. Th
46、ere are many kinds of light emitting devices. However, this part of ISO 17321 describes a programmable light emission system using typical LEDs. Figure 2 shows typical spectral power distributions of a number of LEDs. These LEDs will be intensity-modulated and mixed (integrated) to produce a require
47、d spectral power distribution. NOTE 2 Pulse width and interval modulation for intensity modulation is applicable. NOTE 3 DSCs with automatic exposure control and automatic white balance cannot be applied for colour calibration using this system.2 ISO 2016 All rights reserved PD ISO/TS 17321-4:2016 I
48、SO/TS 17321-4:2016(E) Key 1 uniform light emission on the output window 2 output window 3 light emitting device array 4 integrating sphere F i g u r e 1 S c h e m a t i c c o n f i g u r a t i o n o f t h e p r o g r a m m a b l e l i g h t e m i s s i o n s y s t e m Figure 2 Example of spectral po
49、wer distributions for a chosen set of LEDs 4.2 Hardware requirements 4.2.1 General This Clause is to describe a light emitting system for DSC colour characterization that uses an integrating sphere. ISO 2016 All rights reserved 3 PD ISO/TS 17321-4:2016 ISO/TS 17321-4:2016(E) 4.2.2 Operating condition The light emitting system shall be designed to operate consistently under the following ranges. NOTE “Temperature” condition was referred from ISO 12646. Temperature: 18
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