SIST ISO 12233:2014

INTERNATIONAL ISO
STANDARD 12233
Second edition
2014-02-15
Photography — Electronic still picture
imaging — Resolution and spatial
frequency responses
Photographie — Imagerie des prises de vues électroniques —
Résolution et réponses en fréquence spatiale
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms 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 . 5
4.4 Camera settings . 5
4.5 White balance. 6
4.6 Luminance and colour measurements . 6
4.7 Gamma correction . 6
5 Visual resolution measurement . 6
5.1 General . 6
5.2 Test chart. 7
5.3 Rules of judgement for visual observation . 8
6 Edge-based spatial frequency response (e-SFR) . 9
6.1 General . 9
6.2 Methodology . 9
7 Sine-based spatial frequency response (s-SFR) measurement .12
8 Presentation of results .13
8.1 General .13
8.2 Resolution .13
8.3 Spatial frequency response (SFR) .14
Annex A (informative) CIPA resolution test chart .17
Annex B (informative) Visual resolution measurement software .23
Annex C (informative) 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
Annex F (normative) Sine wave Spatial Frequency Response (s-SFR) analysis algorithm .35
Annex G (informative) Colour-filtered resolution measurements .40
Annex H (informative) Units and summary metrics .42
Annex I (informative) Original test chart defined in ISO 12233:2000 .45
Bibliography .49
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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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/directives).
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 12233:2000), which has been technically
revised.
iv © ISO 2014 – All rights reserved

Introduction
0.1 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
International Standard defines terminology, test charts, and test methods for performing resolution
measurements for analog and digital electronic still-picture cameras.
0.2 Technical background
For consumer digital cameras, the term resolution is often incorrectly interpreted as the number of
addressable photoelements. While there are existing protocols for determining camera pixel counts,
these should not be confused with the interpretation of resolution as addressed in this International
Standard. Qualitatively, resolution is the ability of a camera to optically capture finely spaced detail, and
is usually reported as a single valued metric. Spatial 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 camera. A camera’s 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 compression and gamma correction functions.
While resolution and SFR are related metrics, their difference lies in their comprehensiveness and
utility. As articulated in this International Standard, resolution is a single frequency parameter that
indicates whether the output signal contains a minimum threshold of detail information 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 understood 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
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 specified
SFR level as a modified non-visual resolution value.
In a departure from the first edition of this International Standard, 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 lower 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 yield a phase-averaged SFR response.
A second sine wave-based SFR metrology technique is introduced in this 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 signatures 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 processing 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 test chart defined in this
International Standard 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 individual components of an
electronic still-picture camera, such as the lens.
Some of the measurements described in this International Standard are performed using digital analysis
techniques. They are also applicable with the analogue outputs of the camera by digitizing the analogue
signals if there is adequate digitizing equipment.
0.3 Methods for m
...