ISO 19084:2015

INTERNATIONAL ISO
STANDARD 19084
First edition
2015-12-15
Photography — Digital cameras
— Chromatic displacement
measurements
Photographie — Caméras numériques — Mesurages du
déplacement chromatique
Reference number
ISO 19084:2015(E)
©
ISO 2015

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ISO 19084:2015(E)

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© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

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ISO 19084:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Test conditions and methods . 1
3.1 General . 1
3.2 Apparatus and hardware . 1
3.2.1 Lighting . 2
3.2.2 Test chart . 2
3.3 Arrangement of measuring equipment . 4
3.3.1 Reflective test chart . 4
3.3.2 Transmissive test chart . 4
3.3.3 Positioning of the camera . 5
3.4 Image/camera settings . 6
4 Analytical approach. 6
4.1 General . 6
4.2 Determination of displacement . 6
4.2.1 Dot chart . 6
4.2.2 V pattern chart . 7
4.3 Chromatic displacement (CD) . 8
4.3.1 Numerical definition . . 8
4.4 Radial chromatic displacement (RCD). 9
4.4.1 Numerical definition . . 9
5 Presentations of results .10
5.1 Chromatic displacement .10
5.2 Radial chromatic displacement .11
Annex A (informative) Extracting the dots from the target .13
Bibliography .14
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ISO 19084:2015(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 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.
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 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).
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 the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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The committee responsible for this document is ISO/TC 42, Photography.
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ISO 19084:2015(E)

Introduction
Digital still camera images sometimes experience a type of artefact known as chromatic displacement.
These artefacts generally appear as colour fringe at boundaries that separate dark and light features.
This International Standard defines this type of artefact as chromatic displacement regardless of the
source. In the case of multi-sensor digital still cameras, chromatic displacement may be caused by
optical, mechanical and electrical factors. In the case of single sensor digital still cameras, there are
almost no mechanical and electrical factors, so the chromatic displacement is mainly generated by
optical factors and artefacts caused by a mosaic colour filter array. Optical aberrations include lateral
chromatic aberration, longitudinal chromatic aberration and comatic aberration.
Lateral chromatic aberration arises when the size of an image changes with the wavelengths of light.
Because of this, lateral chromatic aberration is more conspicuous at the peripheral part of the image.
Lateral chromatic aberration is rotationally symmetric in an ideal case; however this might not be the
case due to manufacturing tolerances.
Longitudinal chromatic aberration arises when the back focus changes with the wavelength of light.
Unlike lateral chromatic aberration, longitudinal chromatic aberration may be conspicuous not only in
the peripheral part of the image but also in the central portion of the image.
Chromatic displacement by comatic aberration arises when the characteristic of a comatic aberration
changes with the wavelengths of light. This phenomenon, known as purple fringe or a colour fringe,
is conspicuous at the peripheral part of the image like lateral chromatic aberration. In many cases,
comatic aberration can be reduced by using a larger lens f-number (smaller aperture).
Chromatic displacement is emphasized or reduced by image processing.
To measure chromatic displacement, IEC 61146-2 is established by IEC and CIPA DCG-002-2012 based
on IEC 61146-2 is also established by CIPA. Furthermore, P1858 - Standard for Camera Phone Image
Quality(CPIQ) is being developed by IEEE.
This International Standard defines two methods for measuring, the Chromatic displacement and
Radial chromatic displacement. Chromatic displacement measures total chromatic displacement
encompassing all factors as provided by IEC 61146-2 and CIPA DCG-002-2012. Radial chromatic
displacement which measures optical aberration is based on a method developed by the CPIQ and is a
main factor in the chromatic aberration of a single sensor digital still camera.
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INTERNATIONAL STANDARD ISO 19084:2015(E)
Photography — Digital cameras — Chromatic
displacement measurements
1 Scope
This International Standard specifies the definition of chromatic displacement for digital still
cameras, test patterns, measurement conditions and methods, so as to enable the comparison of the
results of measurement.
The methods of measurement are designed to enable the assessment of the performance of digital still
cameras by using image data output by the digital still cameras.
This International Standard does not specify the allowable amount of chromatic displacement.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
chromatic displacement
shift in location of features of different colours in the output image caused by optical, mechanical,
electrical and image processing factors
Note 1 to entry: Optical factor include lateral chromatic aberration, longitudinal chromatic aberration,
characteristic comatic aberration and others.
Note 2 to entry: It is the displacement of the red (R) and the blue (B) channel in relation to the green (G) channel
in an output image.
Note 3 to entry: Chromatic displacement is evaluated by measuring the chromatic displacement in the lateral
direction in the image.
2.2
radial chromatic displacement
radial shift in location of different colours in the output image caused by the optical factor called lateral
chromatic aberration that may then be influenced by mechanical, electrical and image processing factors
3 Test conditions and methods
3.1 General
The measurement shall be carried out using the digital signals of the output images from the digital
still camera with which the test chart is captured.
The following measurement conditions should be used as nominal conditions when measuring the
chromatic displacement of a digital still camera. If it is not possible or appropriate to achieve these nominal
operating conditions, the actual operating conditions shall be listed along with the reported results.
3.2 Apparatus and hardware
Each test chart shall be specified, together with the lighting conditions such as illuminance, luminance
and colour temperature of illumination.
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ISO 19084:2015(E)

3.2.1 Lighting
Colour temperature of illumination shall be 5 700 K ± 1 000 K. This International Standard does not
require a specific illumination level. A level between 1 000 lx to 2 000 lx (in the case of transmissive
2 2
chart, between 318 cd/m to 637 cd/m ) is recommended. Special measurement purposes may require
other levels. Non-uniformity in illuminance (or luminance) on the chart shall be less than 10 %. The
light source(s) should be positioned to provide uniform illumination and produce no glare or specular
reflections from the target.
3.2.2 Test chart
3.2.2.1 General
Examples of the test charts are shown in Figure 1 and Figure 2. They can be either reflective test charts
or transmissive test chart. The black pattern such as dots or Vs shall represent less than 20 % of the total
surface of the image. The chart contrast level should at least be 40:1 and not be higher than 10 000:1.
3.2.2.2 Dot chart
The dot chart contains black circular dots placed on a perfectly regular square grid on a uniform white
background. Chromatic displacement and radial chromatic displacement are calculated by measuring
the centre positions of the circular dots. The size and the number of dots should be adjusted depending
on the number of pixels of the camera and the shooting distance. In the image of the chart, the number of
dots on a 4:3 image should be no less than 20 × 15 dots and the diameter of each dot shall be no less than
10 pixels. For a detailed description on how to determine the dots and dot centres in the chart, see 4.2.1.
Figure 1 — Dot chart
NOTE ISO 17850, Geometric distortion measurement also adopts the dot chart. Use of the
...