SIST ISO 20462-3:2011
Photography - Psychophysical experimental methods for estimating image quality - Part 3: Quality ruler method
Photography - Psychophysical experimental methods for estimating image quality - Part 3: Quality ruler method
ISO 20462-3:2005 specifies: the nature of a quality ruler; hardcopy and softcopy implementations of quality rulers; how quality rulers may be generated or obtained; and the standard quality scale (SQS), a fixed numerical scale that may be measured using quality rulers.
Photographie - Méthodes psychophysiques expérimentales pour estimer la qualité d'image - Partie 3: Méthode <<quality ruler>>
Fotografija - Psihofizične eksperimentalne metode za ocenjevanje slikovne kakovosti - 3. del: Metoda referenčne kakovosti
Ta del ISO 20462 določa: a) naravo orodja za referenčno kakovost; b) izvedbo orodij za referenčno kakovost v papirnati in elektronski obliki; c) kako nastanejo orodja za referenčno kakovost oz. kako jih pridobimo; in d) standardno lestvico kakovosti (SQS), ustaljeno številčno lestvico, ki se lahko meri z orodji za referenčno kakovost.
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 20462-3
First edition
2005-11-01
Photography — Psychophysical
experimental methods for estimating
image quality —
Part 3:
Quality ruler method
Photographie — Méthodes psychophysiques expérimentales pour
estimer la qualité d'image —
Partie 3: Méthode «quality ruler»
Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2005
All rights reserved. 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
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Quality ruler experiments . 5
4.1 General properties of quality rulers. 5
4.2 Experimental conditions and reported results . 5
4.3 Attributes varied in quality rulers . 5
5 Hardcopy quality ruler implementation. 6
5.1 Physical apparatus. 6
5.2 Reference stimuli. 7
6 Softcopy quality ruler implementation . 8
6.1 Physical apparatus. 8
6.2 Reference stimuli. 8
6.3 Controlling software. 8
7 Generation of quality ruler stimuli . 9
7.1 General requirements. 9
7.2 Modulation transfer functions (MTFs) . 9
7.3 Scene-dependent ruler calibration. 11
8 Standard quality scale (SQS) determinations. 12
8.1 Properties of the SQS. 12
8.2 Experimental requirements. 12
Annex A (informative) Sample instructions for a hardcopy quality ruler experiment. 13
Annex B (informative) Sample instructions for a softcopy quality ruler experiment. 15
Annex C (informative) Sample code of a binary search routine for the softcopy quality ruler. 17
Annex D (informative) Calibration of the standard quality scale (SQS) and its reference stimuli. 18
Annex E (informative) Example of results from quality ruler experiments . 20
Bibliography . 24
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 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-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 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 requires approval by at least 75 % of the member bodies casting a vote.
ISO 20462-3 was prepared by Technical Committee ISO/TC 42, Photography.
ISO 20462 consists of the following parts, under the general title Photography — Psychophysical experimental
methods for estimating image quality:
⎯ Part 1: Overview of psychophysical elements
⎯ Part 2: Triplet comparison method
⎯ Part 3: Quality ruler method
iv © ISO 2005 – All rights reserved
Introduction
There are many circumstances under which it is desirable to quantify image quality in a standardized fashion
that facilitates interpretation of results within a given experiment and/or comparison of results between
different experiments. Such information can be of value in assessing the performance of different capture or
display devices, image processing algorithms, etc. under various conditions. However, the choice of the best
psychometric method for a particular application may be difficult to make, and interpretation of the rating
scales produced by the numerical analyses is frequently ambiguous. Furthermore, none of the commonly
used rating techniques provides an efficient mechanism for calibration of the results against a standardised
numerical scale or associated physical references, which is desirable when results of different experiments
are to be compared or integrated.
The three parts of ISO 20462 address the need for documented means of determining image quality in a
calibrated fashion. Part 1 provides an overview of practical psychophysics and aids in identifying the better
[1][2]
choice between the two alternative approaches described in Part 2 (triplet comparison method ) and Part 3
[3]
(quality ruler method ). These two techniques are complementary and together are sufficient to span a wide
range of practical applications. Parts 2 and 3 document both specific experimental methods and associated
data reduction techniques. It is the intent of these methods to produce results that are not merely directional in
nature, but are expressed in terms of relative or fixed scales that are calibrated in terms of just noticeable
differences (JNDs), so that the significance of experimentally measured stimulus differences is readily
ascertained.
The quality ruler method described in this part of ISO 20462 is particularly suitable for measuring quality
differences exceeding one JND. The ratings given by an observer can be converted to JND values in real time,
rather than having to wait until the entire experimental data set has been collected and analysed. Furthermore,
with suitable reference stimuli, the quality ruler method permits the results to be reported using the standard
quality scale (SQS), a fixed numerical scale that:
a) is anchored against physical standards;
b) has one unit corresponding to one JND; and
c) has a zero point corresponding to an image having little identifiable information content.
Reflection prints calibrated against the absolute SQS, which are referred to as standard reference stimuli
(SRS), will be available on the I3A website. This part of ISO 20462 also describes how users can conveniently
generate their own quality ruler images with correct relative calibrations and, if desired, calibrate them
absolutely against the SRS.
The International Organization for Standardization (ISO) draws attention to the fact that it is claimed that
compliance with this document may involve the use of US Patent Numbers 6,639,999 and 6,658,139
concerning the quality ruler given in Clauses 4 to 6.
ISO takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he is willing to negotiate licences under reasonable and
non-discriminatory terms and conditions with applicants throughout the world. In this respect, the statement of
the holder of this patent right is registered with ISO. Patent inquiries may be addressed to:
General Council and Senior Vice President
Eastman Kodak Company
345 State Street
Rochester, NY 14650
USA
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those identified above. ISO shall not be held responsible for identifying any or all such patent
rights.
vi © ISO 2005 – All rights reserved
INTERNATIONAL STANDARD ISO 20462-3:2005(E)
Photography — Psychophysical experimental methods for
estimating image quality —
Part 3:
Quality ruler method
1 Scope
This part of ISO 20462 specifies:
a) the nature of a quality ruler;
b) hardcopy and softcopy implementations of quality rulers;
c) how quality rulers may be generated or obtained; and
d) the standard quality scale (SQS), a fixed numerical scale that may be measured using quality rulers.
2 Normative references
The 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 3664, Viewing conditions — Graphic technology and photography
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
artefactual attribute
attribute of image quality that, when evident in an image, nearly always leads to a loss of overall image quality
EXAMPLE Examples of artefactual attributes include noise and aliasing.
NOTE The commonly used terms defect and impairment are similar in meaning.
3.2
attribute
aspect, dimension, or component of overall image quality
cf. artefactual attribute (3.1) and preferential attribute (3.10)
EXAMPLE Examples of image quality attributes include image structure properties such as sharpness and noise;
colour and tone reproduction properties such as contrast, colour balance, and relative colourfulness; and digital artefacts
such as aliasing, contouring, and compression defects.
3.3
image quality
impression of the overall merit or excellence of an image, as perceived by an observer neither associated with
the act of photography nor closely involved with the subject matter depicted
NOTE The purpose of defining image quality in terms of third-party (uninvolved) observers is to eliminate sources of
variability that arise from more idiosyncratic aspects of image perception and pertain to attributes outside the control of
imaging system designers.
3.4
instructions
set of directions given to the observer for performing the psychophysical evaluation task
3.5
just noticeable difference
JND
stimulus difference that leads to a 75:25 proportion of responses in a paired comparison task
cf. quality JND (3.12)
3.6
magnitude estimation method
psychophysical method involving the assignment of a numerical value to each test stimulus that is proportional
to image quality; typically, a reference stimulus with an assigned numerical value is present to anchor the
rating scale
NOTE The numerical scale resulting from a magnitude estimation experiment is usually assumed to constitute a ratio
scale which, ideally, is a scale in which a constant percentage change in value corresponds with one JND. In practice,
modest deviations from this behaviour occur, complicating the transformation of the rating scale into units of JNDs without
...
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.VOLNRYQHPhotographie - Méthodes psychophysiques expérimentales pour estimer la qualité d'image - Partie 3: Méthode <>Photography - Psychophysical experimental methods for estimating image quality - Part 3: Quality ruler method37.040.01Fotografija na splošnoPhotography in generalICS:Ta slovenski standard je istoveten z:ISO 20462-3:2005SIST ISO 20462-3:2011en01-julij-2011SIST ISO 20462-3:2011SLOVENSKI
STANDARD
Reference numberISO 20462-3:2005(E)© ISO 2005
INTERNATIONAL STANDARD ISO20462-3First edition2005-11-01Photography — Psychophysical experimental methods for estimating image quality — Part 3: Quality ruler method Photographie — Méthodes psychophysiques expérimentales pour estimer la qualité d'image — Partie 3: Méthode «quality ruler»
©
ISO 2005 All rights reserved. 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 ISO's member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyright@iso.org Web www.iso.org Published in Switzerland
ii
iiiContents Page Foreword.iv Introduction.v 1 Scope.1 2 Normative references.1 3 Terms and definitions.1 4 Quality ruler experiments.5 4.1 General properties of quality rulers.5 4.2 Experimental conditions and reported results.5 4.3 Attributes varied in quality rulers.5 5 Hardcopy quality ruler implementation.6 5.1 Physical apparatus.6 5.2 Reference stimuli.7 6 Softcopy quality ruler implementation.8 6.1 Physical apparatus.8 6.2 Reference stimuli.8 6.3 Controlling software.8 7 Generation of quality ruler stimuli.9 7.1 General requirements.9 7.2 Modulation transfer functions (MTFs).9 7.3 Scene-dependent ruler calibration.11 8 Standard quality scale (SQS) determinations.12 8.1 Properties of the SQS.12 8.2 Experimental requirements.12 Annex A (informative) Sample instructions for a hardcopy quality ruler experiment.13 Annex B (informative) Sample instructions for a softcopy quality ruler experiment.15 Annex C (informative) Sample code of a binary search routine for the softcopy quality ruler.17 Annex D (informative) Calibration of the standard quality scale (SQS) and its reference stimuli.18 Annex E (informative) Example of results from quality ruler experiments.20 Bibliography.24
vIntroduction There are many circumstances under which it is desirable to quantify image quality in a standardized fashion that facilitates interpretation of results within a given experiment and/or comparison of results between different experiments. Such information can be of value in assessing the performance of different capture or display devices, image processing algorithms, etc. under various conditions. However, the choice of the best psychometric method for a particular application may be difficult to make, and interpretation of the rating scales produced by the numerical analyses is frequently ambiguous. Furthermore, none of the commonly used rating techniques provides an efficient mechanism for calibration of the results against a standardised numerical scale or associated physical references, which is desirable when results of different experiments are to be compared or integrated. The three parts of ISO 20462 address the need for documented means of determining image quality in a calibrated fashion. Part 1 provides an overview of practical psychophysics and aids in identifying the better choice between the two alternative approaches described in Part 2 (triplet comparison method[1][2]) and Part 3 (quality ruler method[3]). These two techniques are complementary and together are sufficient to span a wide range of practical applications. Parts 2 and 3 document both specific experimental methods and associated data reduction techniques. It is the intent of these methods to produce results that are not merely directional in nature, but are expressed in terms of relative or fixed scales that are calibrated in terms of just noticeable differences (JNDs), so that the significance of experimentally measured stimulus differences is readily ascertained. The quality ruler method described in this part of ISO 20462 is particularly suitable for measuring quality differences exceeding one JND. The ratings given by an observer can be converted to JND values in real time, rather than having to wait until the entire experimental data set has been collected and analysed. Furthermore, with suitable reference stimuli, the quality ruler method permits the results to be reported using the standard quality scale (SQS), a fixed numerical scale that: a) is anchored against physical standards; b) has one unit corresponding to one JND; and c) has a zero point corresponding to an image having little identifiable information content. Reflection prints calibrated against the absolute SQS, which are referred to as standard reference stimuli (SRS), will be available on the I3A website. This part of ISO 20462 also describes how users can conveniently generate their own quality ruler images with correct relative calibrations and, if desired, calibrate them absolutely against the SRS. The International Organization for Standardization (ISO) draws attention to the fact that it is claimed that compliance with this document may involve the use of US Patent Numbers 6,639,999 and 6,658,139 concerning the quality ruler given in Clauses 4 to 6. ISO takes no position concerning the evidence, validity and scope of this patent right. The holder of this patent right has assured ISO that he is willing to negotiate licences under reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect, the statement of the holder of this patent right is registered with ISO. Patent inquiries may be addressed to: General Council and Senior Vice President Eastman Kodak Company 345 State Street Rochester, NY 14650 USA SIST ISO 20462-3:2011
INTERNATIONAL STANDARD ISO 20462-3:2005(E) © ISO 2005 – All rights reserved
1Photography — Psychophysical experimental methods for estimating image quality — Part 3: Quality ruler method 1 Scope This part of ISO 20462 specifies: a) the nature of a quality ruler; b) hardcopy and softcopy implementations of quality rulers; c) how quality rulers may be generated or obtained; and d) the standard quality scale (SQS), a fixed numerical scale that may be measured using quality rulers. 2 Normative references The 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 3664, Viewing conditions — Graphic technology and photography 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 artefactual attribute attribute of image quality that, when evident in an image, nearly always leads to a loss of overall image quality EXAMPLE Examples of artefactual attributes include noise and aliasing. NOTE The commonly used terms defect and impairment are similar in meaning. 3.2 attribute aspect, dimension, or component of overall image quality cf. artefactual attribute (3.1) and preferential attribute (3.10) EXAMPLE Examples of image quality attributes include image structure properties such as sharpness and noise; colour and tone reproduction properties such as contrast, colour balance, and relative colourfulness; and digital artefacts such as aliasing, contouring, and compression defects. SIST ISO 20462-3:2011
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.