1、BSI Standards PublicationBS ISO 19084:2015Photography Digital cameras Chromatic displacementmeasurementsBS ISO 19084:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 19084:2015.The UK participation in its preparation was entrusted to TechnicalCommittee CPW/
2、42, Photography.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2015.Published
3、by BSI Standards Limited 2015ISBN 978 0 580 86651 7ICS 37.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 December 2015.Amendments/corrigenda issued since
4、 publicationDate T e x t a f f e c t e dBS ISO 19084:2015 ISO 2015Photography Digital cameras Chromatic displacement measurementsPhotographie Camras numriques Mesurages du dplacement chromatiqueINTERNATIONAL STANDARDISO19084First edition2015-12-15Reference numberISO 19084:2015(E)BS ISO 19084:2015ISO
5、 19084:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in SwitzerlandAll 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 photocopyi
6、ng, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 1
7、1Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 19084:2015ISO 19084:2015(E)Foreword ivIntroduction v1 Scope . 12 Terms and definitions . 13 Test conditions and methods . 13.1 General . 13.2 Apparatus and hardware 13.2.1 Lighting 23.2.2 Test chart 23.3 Arrangement of measuring equipment . 43.3
8、.1 Reflective test chart . 43.3.2 Transmissive test chart 43.3.3 Positioning of the camera . 53.4 Image/camera settings 64 Analytical approach. 64.1 General . 64.2 Determination of displacement 64.2.1 Dot chart . 64.2.2 V pattern chart . 74.3 Chromatic displacement (CD) 84.3.1 Numerical definition .
9、 84.4 Radial chromatic displacement (RCD) 94.4.1 Numerical definition . 95 Presentations of results .105.1 Chromatic displacement 105.2 Radial chromatic displacement . 11Annex A (informative) Extracting the dots from the target .13Bibliography .14 ISO 2015 All rights reserved iiiContents PageBS ISO
10、19084:2015ISO 19084:2015(E)ForewordISO (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
11、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 Commi
12、ssion (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 sh
13、ould 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 i
14、dentifying 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 for the conv
15、enience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword
16、 - Supplementary informationThe committee responsible for this document is ISO/TC 42, Photography.iv ISO 2015 All rights reservedBS ISO 19084:2015ISO 19084:2015(E)IntroductionDigital still camera images sometimes experience a type of artefact known as chromatic displacement. These artefacts generall
17、y 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
18、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
19、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 aberratio
20、n 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 conspicuou
21、s 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 conspi
22、cuous 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 estab
23、lished 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 displacem
24、ent. 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
25、a single sensor digital still camera. ISO 2015 All rights reserved vBS ISO 19084:2015BS ISO 19084:2015Photography Digital cameras Chromatic displacement measurements1 ScopeThis International Standard specifies the definition of chromatic displacement for digital still cameras, test patterns, measure
26、ment 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
27、the allowable amount of chromatic displacement.2 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.2.1chromatic displacementshift in location of features of different colours in the output image caused by optical, mechanical, electrical and image proce
28、ssing factorsNote 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.N
29、ote 3 to entry: Chromatic displacement is evaluated by measuring the chromatic displacement in the lateral direction in the image.2.2radial chromatic displacementradial shift in location of different colours in the output image caused by the optical factor called lateral chromatic aberration that ma
30、y then be influenced by mechanical, electrical and image processing factors3 Test conditions and methods3.1 GeneralThe 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 conditi
31、ons 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
32、Each test chart shall be specified, together with the lighting conditions such as illuminance, luminance and colour temperature of illumination.INTERNATIONAL STANDARD ISO 19084:2015(E) ISO 2015 All rights reserved 1BS ISO 19084:2015ISO 19084:2015(E)3.2.1 LightingColour temperature of illumination sh
33、all 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 chart, between 318 cd/m2to 637 cd/m2) is recommended. Special measurement purposes may require other levels. Non-uniformity in illumin
34、ance (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 chart3.2.2.1 GeneralExamples of the test charts are shown in Figure 1 and Figure 2. They can be e
35、ither 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 chartThe dot chart contains black circular dots
36、 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
37、 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 chartN
38、OTE ISO 17850, Geometric distortion measurement also adopts the dot chart. Use of the dot chart may reduce the workload required for camera characterization.2 ISO 2015 All rights reservedBS ISO 19084:2015ISO 19084:2015(E)3.2.2.3 V pattern chartThe V pattern chart enables the displacement to be measu
39、red in both the horizontal and vertical directions by only measuring the displacement at reproduced positions in only the horizontal direction. The method for extracting the geometric values is described in 4.2.2.HV0,5H0,7H0,9H0,5V0,7V0,9VV/80V/10V/20V/8090XX22332434263541 42 43 44 45 46 47Figure 2
40、V pattern chart3.2.2.4 Requirement for the chart planarityNon-planarity can be caused by bending of a chart.Requirement for the chart planarity is:Surface deviation which is a height or depth from the reference plane (indicated as bending “l1” in Figure 3) shall be less than 1,5 % of the width of th
41、e chart.NOTE The required accuracy for a specific measurement sets the requirement for the chart planarity as follows.For small bending, “l3” is equal to half the width of the chart to which all numbers are normalized. If bending “l1” occurs in a chart the effective chart width seen by the camera is
42、 “l2”. The difference between l3and l2causes the deviation in % measured due to the bending of the chart and is calculated by (1 l2/l3) 100.The International Standard requirement for local geometric distortion measurement should be a maximum error of 0,045 % due to deviation in planarity of the char
43、t. This equals a maximum deviation in planarity of 3 %. And 3 % of half the width equals to 1,5 % of the full width of the chart. ISO 2015 All rights reserved 3BS ISO 19084:2015ISO 19084:2015(E)Figure 3 Explanation for the chart planarity and its effect on measured value3.3 Arrangement of measuring
44、equipment3.3.1 Reflective test chartThe arrangement of the measuring equipment for a reflective test chart shall be set up as shown in Figure 4. The camera shall be positioned such that it casts no shadow on the chart. The background of the test chart shall be matte black wall or black surround.Matt
45、e black wall or black surroundTest chartLampLampDigital stillcamera Distance isadjusted toframethe test chart Bafg976les to prevent directillumination of thecamera lens by the lampsFigure 4 Arrangement of measuring equipment for reflective test chart3.3.2 Transmissive test chartThe arrangement of th
46、e measuring equipment for a transmissive test chart shall be set up as shown in Figure 5. Instead of a light box, an integrating sphere may be used. Regardless of which light source is used, the illumination shall be diffuse and uniform on the chart plane consistent with the requirement in 3.2.1.4 I
47、SO 2015 All rights reservedBS ISO 19084:2015ISO 19084:2015(E)Test chartDigital stillcameraLight boxDistance isadjusted toframethe test chart Figure 5 Arrangement of measuring equipment for transmissive test chart3.3.3 Positioning of the cameraThe chart needs to be orthogonal to the optical axis. The
48、 alignment can be performed using a mirror set up on the target plane (i.e. parallel to the target plane) as shown in Figure 6.Pan, tilt and laterally displace the camera position to the left, right, up and down until the centre point of the taking lens in the image of the camera in the viewfinder i
49、s at the image centre.Figure 6 Alignment of the camera with the target plane using a mirrorIf the mirror is not available or the positioning method is not applicable, a manual alignment using the lines of dots in the chart shall be performed so that the intersection of the central horizontal and vertical lines of the dots is in the centre of the image. For each horizontal line, the lines shall be oriented parallel to the horizontal image borders meaning that the line shall be at the same image height for the same distan
