1、BS ISO 12233:2017 Photography Electronic still picture imaging Resolution and spatial frequency responses BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 12233:2017 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO 12233
2、:2017. It supersedes BS ISO 12233:2014 which is withdrawn. 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
3、 all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2017. Published by BSI Standards Limited 2017 ISBN 978 0 580 94951 7 ICS 37.040.10 Compliance with a British Standard cannot confer immunity from legal obligations. This
4、British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2017. Amendments/corrigenda issued since publication Date T e x t a f f e c t e dBS ISO 12233:2017 ISO 2017 Photography Electronic still picture imaging Resolution and spatial frequency re
5、sponses Photographie Imagerie des prises de vues lectroniques Rsolution et rponses en frquence spatiale INTERNATIONAL STANDARD ISO 12233 Third edition 2017-01 Reference number ISO 12233:2017(E)BS ISO 12233:2017ISO 12233:2017(E)ii ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2017, Pu
6、blished 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, including photocopying, or posting on the internet or an intranet, without prior written permission. Perm
7、ission 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, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.orgBS ISO 12233:2017ISO 12233:201
8、7(E)Foreword v Introduction vi 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Test conditions . 5 4.1 Test chart illumination . 5 4.2 Camera framing and lens focal length setting 5 4.3 Camera focusing . 6 4.4 Camera settings 6 4.5 White balance. 6 4.6 Luminance and colour measur
9、ements . 6 4.7 Gamma correction 6 5 Visual resolution measurement . 7 5.1 General . 7 5.2 Test chart 7 5.2.1 General 7 5.2.2 Material 7 5.2.3 Size . 7 5.2.4 Test patterns 7 5.2.5 Test pattern modulation 8 5.2.6 Positional tolerance . 8 5.3 Rules of judgement for visual observation . 8 5.3.1 Rules of
10、 judgement 8 5.3.2 An example of a correct visual judgement . 9 6 Edge-based spatial frequency response (e-SFR) . 9 6.1 General . 9 6.2 Methodology 10 6.2.1 Selection of the edge region of interest (ROI) 10 6.2.2 Transformation into effective exposure 10 6.2.3 Estimation of the location of the edge
11、10 6.2.4 Formation of a super-sampled line spread function array .12 6.2.5 Computation of the e-SFR .13 7 Sine-based spatial frequency response (s-SFR) measurement .13 8 Presentation of results 14 8.1 General 14 8.2 Resolution 14 8.2.1 General.14 8.2.2 Basic presentation .14 8.2.3 Representative pre
12、sentation 14 8.3 Spatial frequency response (SFR) .15 8.3.1 General.15 8.3.2 Spatial frequency response 15 8.3.3 Report of resolution value derived from the s-SFR .16 Annex A (informative) CIPA resolution test chart 17 Annex B (informative) Visual resolution measurement software 23 Annex C (informat
13、ive) Low contrast edge SFR test chart with OECF patches 28 Annex D (normative) Edge spatial frequency response (e-SFR) algorithm 30 Annex E (normative) Sine wave star test chart .33 ISO 2017 All rights reserved iii Contents PageBS ISO 12233:2017ISO 12233:2017(E)Annex F (normative) Sine wave spatial
14、frequency response (s-SFR) analysis algorithm .35 Annex G (informative) C olour-filt er ed r esolution measur ements .39 Annex H (informative) Units and summary metrics .41 Annex I (informative) Original t est chart defined in ISO 12233:2000 .44 Bibliography .48 iv ISO 2017 All rights reservedBS ISO
15、 12233:2017ISO 12233:2017(E) Foreword ISO (the International Organization for Standardization) 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 interest
16、ed 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-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Co
17、mmission (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 ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO document
18、s 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 possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsib
19、le 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 patent declarations received (see www .iso .org/ patents). Any trade name used in this document is information given
20、for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformit y assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Tr
21、ade (TBT) see the following URL: www . i s o .org/ iso/ foreword .html. The committee responsible for this document is ISO/TC 42, Photography. This third edition cancels and replaces the second edition (ISO 12233:2014), of which it constitutes a minor revision with changes in Annex D. ISO 2017 All r
22、ights reserved vBS ISO 12233:2017ISO 12233:2017(E) Introduction Purpose The spatial resolution capability is an important attribute of an electronic still-picture camera. Resolution measurement standards allow users to compare and verify spatial resolution measurements. This document defines termino
23、logy, test charts, and test methods for performing resolution measurements for analogue and digital electronic still-picture cameras. Technical background For consumer digital cameras, the term resolution is often incorrectly interpreted as the number of addressable photoelements. While there are ex
24、isting protocols for determining camera pixel counts, these are not to be confused with the interpretation of resolution as addressed in this document. Qualitatively, resolution is the ability of a camera to optically capture finely spaced detail, and is usually reported as a single valued metric. S
25、patial frequency response (SFR) is a multi-valued metric that measures contrast loss as a function of spatial frequency. Generally, contrast decreases as a function of spatial frequency to a level where detail is no longer visually resolved. This limiting frequency value is the resolution of the cam
26、era. A cameras resolution and its SFR are determined by a number of factors. These include, but are not limited to, the performance of the camera lens, the number of addressable photoelements in the optical imaging device, and the electrical circuits in the camera, which can include image compressio
27、n and gamma correction functions. While resolution and SFR are related metrics, their difference lies in their comprehensiveness and utility. As articulated in this document, resolution is a single frequency parameter that indicates whether the output signal contains a minimum threshold of detail in
28、formation for visual detection. In other words, resolution is the highest spatial frequency that a candidate camera can usefully capture under cited conditions. It can be very valuable for rapid manufacturing testing, quality control monitoring, or for providing a simple metric that can be easily un
29、derstood by end users. The algorithm used to determine resolution has been tested with visual experiments using human observers and correlates well with their estimation of high frequency detail loss. SFR is a numerical description of how contrast is changed by a camera as a function of the spatial
30、frequencies that describe the contrast. It is very beneficial for engineering, diagnostic, and image evaluation purposes and serves as an umbrella function from which such metrics as sharpness and acutance are derived. Often, practitioners will select the spatial frequency associated with a specifie
31、d SFR level as a modified non-visual resolution value. In a departure from the first edition of this document, two SFR measurements are described. Additionally, the first SFR metrology method, edge-based spatial frequency response, is identical to that described in the first edition, except that a l
32、ower contrast edge is used for the test chart. Regions of interest (ROI) near slanted vertical and horizontal edges are digitized and used to compute the SFR levels. The use of a slanted edge allows the edge gradient to be measured at many phases relative to the image sensor photoelements and to yie
33、ld a phase-averaged SFR response. A second sine wave-based SFR metrology technique is introduced in the second edition. Using a sine wave modulated target in a polar format (e.g. Siemens star), it is intended to provide an SFR response that is more resilient to ill-behaved spatial frequency signatur
34、es introduced by the image content driven processing of consumer digital cameras. In this sense, it is intended to enable easier interpretation of SFR levels from such camera sources. Comparing the results of the edge-based SFR and the sine-based SFR might indicate the extent to which nonlinear proc
35、essing is used. The first step in determining visual resolution or SFR is to capture an image of a suitable test chart with the camera under test. The test chart should include features of sufficiently fine detail and frequency content such as edges, lines, square waves, or sine wave patterns. The t
36、est chart defined in this document has been designed specifically to evaluate electronic still-picture cameras. It has not necessarily been designed to evaluate other electronic imaging equipment such as input scanners, CRT displays, hard- copy printers, or electro-photographic copiers, nor individu
37、al components of an electronic still-picture camera, such as the lens.vi ISO 2017 All rights reservedBS ISO 12233:2017ISO 12233:2017(E) Some of the measurements described in this document are performed using digital analysis techniques. They are also applicable with the analogue outputs of the camer
38、a by digitizing the analogue signals if there is adequate digitizing equipment. Methods for measuring SFR and resolution Selection rationale and guidance This section is intended to provide more detailed rationale and guidance for the selection of the different resolution metrology methods presented
39、 in this document. While resolution metrology of analogue optical systems, by way of spatial frequency response, is well established and largely consistent between methodologies (e.g. sine waves, lines, edges), metrology data for such systems are normally captured under well-controlled conditions wh
40、ere the required data linearity and spatial isotropy assumptions hold. Generally, it is not safe to assume these conditions for files from many digital cameras, even under laboratory capture environments. Exposure and image content dependent image processing of the digital image file before it is pr
41、ovided as a finished file to the user prevents this. This processing yields different SFR responses depending on the features in the scene or in the case of this document, the target. For instance, in-camera edge detection algorithms might specifically operate on edge features and selectively enhanc
42、e or blur them based on complex nonlinear decision rules. Depending on the intent, these algorithms might also be tuned differently for repetitive scene features such as those found in sine waves or bar pattern targets. Even for constrained camera settings recommended in this document, these nonline
43、ar operators can yield differing SFR results depending on the target feature set. Naturally, this causes confusion on which targets to use, either alone or in combination. Guidelines for selection are offered below. Edges are common features in naturally occurring scenes. They also tend to act as vi
44、sual acuity cues by which image quality is judged and imaging artefacts are manifested. This logic prescribed their use for SFR metrology in the past and current editions of this document. It is also why edge features are prone to image processing in many consumer digital cameras: they are visually
45、important. All other imaging conditions being equal, camera SFRs using different target contrast edge features can be significantly different, especially with respect to their morphology. This is largely due to nonlinear image processing operators and would not occur for strictly linear imaging syst
46、ems. To moderate this behaviour, a lower contrast slanted edge feature (Figure C.1) was chosen to replace the higher contrast version of the first edition. This feature choice still allows for acuity-amenable SFR results beyond the half-sampling frequency and helps prevent nonlinear data clipping th
47、at can occur with high contrast target features. It is also a more reliable rendering of visually important contrast levels in naturally occurring scenes. Sine wave features have long been the choice for directly calculating SFR of analogue imaging systems and they are intuitively satisfying. They h
48、ave been introduced into the second edition based on experiences from the edge-based approach. Because sine waves transition more slowly than edges, they are not prone to being identified as edges in embedded camera processors. As such, the ambiguity that image processing imposes on the SFR can be l
49、argely avoided by their use. Alternatively, if the image processing is influenced by the absence of sharp features, more aggressive processing might be used by the camera. A sine wave starburst test pattern (Figure 6) is adopted in the second edition. With the appropriate analysis software, a sine wave-based SFR can be calculated up to the half-sampling frequency. For the same reasons stated above, the sine wave-based target is also of low contrast and consistent with that of the edge-based version. An added benefit of the targets design over o
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