SIST ISO 20462-3:2014

Photography - Psychophysical experimental methods for estimating image quality - Part 3: Quality ruler method

ISO 20462-3:2012 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 de la règle de qualité

Fotografija - Psihofizične eksperimentalne metode za ocenjevanje slikovne kakovosti - 3. del: Metoda referenčne kakovosti

General Information

• Status: Published
• Publication Date: 03-Feb-2014
• ICS: 37.040.01 - Photography in general
• Technical Committee: GRT - Graphical technology
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 15-Jan-2014
• Due Date: 22-Mar-2014
• Completion Date: 04-Feb-2014
• Ref Project: ISO 20462-3:2012 - Photography — Psychophysical experimental methods for estimating image quality — Part 3: Quality ruler method

Relations

• Replaces: SIST ISO 20462-3:2011 - Photography - Psychophysical experimental methods for estimating image quality - Part 3: Quality ruler method
• Effective Date: 01-Mar-2014

Standards Content (Sample)

SLOVENSKI STANDARD
01-marec-2014
1DGRPHãþD
SIST ISO 20462-3:2011
)RWRJUDILMD3VLKRIL]LþQHHNVSHULPHQWDOQHPHWRGH]DRFHQMHYDQMHVOLNRYQH
NDNRYRVWLGHO0HWRGDUHIHUHQþQHNDNRYRVWL
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 de la règle de qualité
Ta slovenski standard je istoveten z: ISO 20462-3:2012
ICS:
37.040.01 Fotografija na splošno Photography in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 20462-3
Second edition
2012-05-15
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 de la règle de qualité
Reference number
©
ISO 2012
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 [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – 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) .10
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 for measuring primary SQS .12
8.3 Experimental requirements for measuring secondary SQS .12
Annex A (informative) Sample instructions for a hardcopy quality ruler experiment .13
Annex B (informative) Sample instructions for softcopy ruler experiments using binary sort
paired comparison .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.19
Annex E (informative) Example of results from quality ruler experiments .21
Annex F (informative) Sample instructions for a softcopy ruler experiment using slider bar matching 25
Bibliography .26
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.
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 20462-3 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 20462-3:2005), which has been technically revised.
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 2012 – 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 standardized numerical
scale or associated physical references, which is desirable when results of different experiments are to be
compared or integrated.
ISO 20462-1, ISO 20462-2 and this part of ISO 20462 address the need for documented means of determining
image quality in a calibrated fashion. ISO 20462-1 provides an overview of practical psychophysics and aids
in identifying the better choice between the two alternative approaches described in ISO 20462-2 (triplet
[2][3][4] [5]
comparison method ) and this part of ISO 20462 (quality ruler method ). These two techniques are
complementary and together are sufficient to span a wide range of practical applications. ISO 20462-2 and this
part of ISO 20462 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 at the Standards Resources link at www.imaging.org. Digital Reference Stimuli (DRS)
will also be provided at the Standards Resources link at www.imaging.org. These images, when displayed on a
high-quality monitor and viewed correctly, will have approximately known absolute SQS values, and accurately
known relative SQS values (JNDs). Included with the images will be software for running softcopy quality ruler
experiments. 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 ensured 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 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 20462-3:2012(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, Graphic technology and photography — Viewing conditions
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
EXAMPLES Noise, 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 (3.11)
EXAMPLES Image structure properties such as sharpness and noise; colour and tone reproduction properties such as
contrast, colour balance, and relative colourfulness; digital artefacts such as aliasing, contouring, and compression defects.
3.3
digital reference stimuli
DRS
set of digital images used in the softcopy r
...

INTERNATIONAL ISO
STANDARD 20462-3
Second edition
2012-05-15
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 de la règle de qualité
Reference number
©
ISO 2012
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 [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – 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) .10
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 for measuring primary SQS .12
8.3 Experimental requirements for measuring secondary SQS .12
Annex A (informative) Sample instructions for a hardcopy quality ruler experiment .13
Annex B (informative) Sample instructions for softcopy ruler experiments using binary sort
paired comparison .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.19
Annex E (informative) Example of results from quality ruler experiments .21
Annex F (informative) Sample instructions for a softcopy ruler experiment using slider bar matching 25
Bibliography .26
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.
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 20462-3 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 20462-3:2005), which has been technically revised.
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 2012 – 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 standardized numerical
scale or associated physical references, which is desirable when results of different experiments are to be
compared or integrated.
ISO 20462-1, ISO 20462-2 and this part of ISO 20462 address the need for documented means of determining
image quality in a calibrated fashion. ISO 20462-1 provides an overview of practical psychophysics and aids
in identifying the better choice between the two alternative approaches described in ISO 20462-2 (triplet
[2][3][4] [5]
comparison method ) and this part of ISO 20462 (quality ruler method ). These two techniques are
complementary and together are sufficient to span a wide range of practical applications. ISO 20462-2 and this
part of ISO 20462 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 at the Standards Resources link at www.imaging.org. Digital Reference Stimuli (DRS)
will also be provided at the Standards Resources link at www.imaging.org. These images, when displayed on a
high-quality monitor and viewed correctly, will have approximately known absolute SQS values, and accurately
known relative SQS values (JNDs). Included with the images will be software for running softcopy quality ruler
experiments. 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 ensured 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 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 20462-3:2012(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, Graphic technology and photography — Viewing conditions
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
EXAMPLES Noise, 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 (3.11)
EXAMPLES Image structure properties such as sharpness and noise; colour and tone reproduction properties such as
contrast, colour balance, and relative colourfulness; digital artefacts such as aliasing, contouring, and compression defects.
3.3
digital reference stimuli
DRS
set of digital images used in the softcopy ruler, which vary in sharpness and are calibrated against the standard
quality scale (SQS) when suitably displayed and viewed
NOTE The DRS will be available at the Standards Resources link at www.imaging.org.
3.4
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.
3.5
instructions
set of directions given to the observer for performing the psychophysical evaluation task
3.6
just noticeable difference
JND
stimulus difference that leads to a 75:25 proportion of responses in
...