1、BSI Standards PublicationBS ISO 15781:2015Photography Digital stillcameras Measuring shootingtime lag, shutter release timelag, shooting rate, and start-uptimeBS ISO 15781:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 15781:2015. It supersedes BS ISO 157
2、81:2013 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photography.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a
3、 contract. Users are responsible for its correct application. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 88099 5 ICS 37.040.10 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under
4、the authority of the Standards Policy and Strategy Committee on 31 March 2015.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e d ISO 2015Photography Digital still cameras Measuring shooting time lag, shutter release time lag, shooting rate, and start-up timePhotographie Camra
5、s numriques Mesurage du dcalage dans le temps de la prise de vue, dcalage dans le temps de louverture de lobjectif, cadence de prise et temps de dmarrageINTERNATIONAL STANDARDISO 15781Second edition 2015-03-15Reference number ISO 15781:2015(E)BS ISO 15781:2015ISO 15781:2015(E)ii ISO 2015 All rights
6、reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015All 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 photocopying, or posting on the internet or an intranet, without prior wr
7、itten permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO
8、15781:2015ISO 15781:2015(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Test conditions . 24.1 Illumination of the test scene . 24.2 The chart and positioning of the digital still camera . 34.3 Battery status . 44.4 Memory card . 44.5 Flash . 45 Measuremen
9、ts . 45.1 Definition of measurement. 45.1.1 General 45.1.2 External measurement .65.1.3 Internal measurement 65.2 Measurement method . 65.2.1 Start-up time . 65.2.2 Shooting time lag . 75.2.3 Shutter release time lag . 85.2.4 Shooting rate . 86 Reporting the results . 9Annex A (informative) Test res
10、ults of methods to start the timing device 10Annex B (informative) Timing device .12Annex C (informative) Measurement by internal method 16Annex D (informative) Examples of reporting the result .23Bibliography .25 ISO 2015 All rights reserved iiiContents PageBS ISO 15781:2015ISO 15781:2015(E)Forewor
11、dISO (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
12、 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 elec
13、trotechnical 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 d
14、rafted 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
15、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 convenience of users and does not cons
16、titute 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 Supplementary information .The c
17、ommittee responsible for this document is ISO/TC 42, Photography.This second edition cancels and replaces the first edition (ISO 15781:2013), of which it constitutes a minor revision.iv ISO 2015 All rights reservedBS ISO 15781:2015ISO 15781:2015(E)IntroductionTaking pictures of a moving target was n
18、early impossible in the early days of digital photography. After pressing the exposure button, it took a significant amount of time to capture the image and the chance to preserve the desired moment was gone.Part of the time between pressing the exposure button and the exposed picture is needed to f
19、ocus while another part is needed to adjust the exposure, etc. This unwelcome, but unavoidable period of time is called the shooting time lag. This is often mixed with the term shutter release time lag which is also defined in this International Standard. Optimized systems are nowadays able to decre
20、ase these time lags.Capturing the different stages of a fast moving object is sometimes very important, especially in areas like sports or people photography. This high shooting rate requires a fast image processing within the digital still camera that can be measured according to the method describ
21、ed in this International Standard.When a photographer decides to capture an image of a changing scene, if his or her digital still camera takes a long time to be ready to shoot once it is turned on, the opportunity to capture the image is lost. This time named start-up time is therefore another impo
22、rtant value which can be determined using this International Standard. ISO 2015 All rights reserved vBS ISO 15781:2015ISO 15781:2015(E)BS ISO 15781:2015Photography Digital still cameras Measuring shooting time lag, shutter release time lag, shooting rate, and start-up time1 ScopeThis International S
23、tandard specifies how to measure and report the shooting time lag, shutter release time lag, shooting rate, and start-up time for digital still cameras including camera modules in phones and tablet computers. It includes a method that uses control signals inside the digital still camera and a method
24、 that determines the timing values without requiring access to the inside of the digital still camera.Depending on the method used to start the timing device, there can be a time lag between the activation of the timing device and the closure of the exposure switch of the digital still camera.This I
25、nternational Standard does not address the measurement of auto focus accuracy and speed at low light conditions.For digital still cameras that continuously shoot images into the buffer, the exposure button only acts as a selector of an image that was taken before the exposure button was pressed. The
26、 methods to measure shutter time lag and shooting time lag do not address this case and cannot be used for this type of digital still camera.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For
27、dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 7589, Photography Illuminants for sensitometry Specifications for daylight, incandescent tungsten and printer3 Terms and definitionsFor the p
28、urposes of this document, the following terms and definitions apply.3.1digital still cameradevice which incorporates an image sensor and produces a digital signal representing a still pictureNote 1 to entry: A digital still camera is typically a portable, hand-held device. The digital signal is usua
29、lly recorded on a removable memory such as a solid-state memory card or magnetic disk.Note 2 to entry: This term is also defined in ISO 12231, ISO 12232, ISO 15739, and ISO 17321-1.3.2shooting time lagtime between pressing the exposure button (firmly depressing the shutter button to the maximum exte
30、nt without introducing a discontinuity) on a digital still camera 3.1 or a module built into a mobile device and the beginning of the exposureNote 1 to entry: This period of time includes all measurements and adjustments (e.g. auto focus and exposure control) a digital still camera needs to make pri
31、or to the beginning of the exposure.INTERNATIONAL STANDARD ISO 15781:2015(E) ISO 2015 All rights reserved 1BS ISO 15781:2015ISO 15781:2015(E)Note 2 to entry: When the exposure button of a digital still camera is pressed, it performs a number of time-consuming measurements and adjustments, e.g. deter
32、mination of the exposure and focus adjustment. The time needed for these procedures is part of the shooting time lag.3.3shutter release time lagtime duration to the time of starting the exposure from the time of fully pressing down the shutter button after having stabilized the focus operation due t
33、o half pressing of the shutter, in case of digital still cameras 3.1 that distinguish between the half pressing and the fully pressingNote 1 to entry: Instead of shutter release time lag, the terms shutter lag and release lag are used in some publications.3.4start-up timetime between switching a dig
34、ital still camera 3.1 on and the moment the camera has reached a standby state 3.6 ready to shootNote 1 to entry: It excludes the initialization of a memory card.3.5shooting ratereciprocal of the time between the beginning of the exposure of an image until the beginning of the exposure of the next i
35、mage3.6standby statestate achieved following the power-up process in which a digital still camera 3.1 is powered on and ready to capture an imageNote 1 to entry: If the digital still camera uses an electronic viewfinder, a preview image is normally displayed during the standby state.3.7pre-capture p
36、ointposition of a user control of a digital still camera 3.1 which activates pre-capture processes such as auto-focus and exposure calculationNote 1 to entry: The pre-capture point is typically reached by pressing an exposure button roughly halfway down.3.8capture pointposition of a user control of
37、a digital still camera 3.1 which activates the image capture operationNote 1 to entry: The capture point is typically reached by fully depressing the exposure button.4 Test conditions4.1 Illumination of the test sceneThe illumination level of the shooting area including the test chart should be even
38、 and above 500 lx and below 5 000 lx. The test scene shall be illuminated in a way that avoids specular reflection (see Figure 1). This can be achieved by using geometry typical for reproduction photography which means positioning the light sources in approximately 45 angle to the surface of the cha
39、rt. The illumination level of the area shall be reported together with the measurements.Timing measurements shall be performed under daylight conditions or a tungsten lamp. Procedures for determining whether the illumination used for OECF measurements is an acceptable match to the daylight illuminan
40、t shall be conducted in accordance with ISO 7589.2 ISO 2015 All rights reservedBS ISO 15781:2015ISO 15781:2015(E)calibrated spectral photometertest chartlight source tungstenFigure 1 Principle for illuminating the target4.2 The chart and positioning of the digital still cameraThe digital still camer
41、a shall be mounted on a solid stand (e.g. heavy tripod) perpendicular to and facing the surface of the chart (see Figure 2).As for the test chart, the chart shall allow the digital still camera to focus easily and allow an easy determination whether the captured image is correctly focused. Examples
42、include a black-and-white checker board or the three-line chart shown in Annex B. If the above condition is met, a typical image assessment chart can be used. Also, the ISO 12233 resolution chart can be placed in the chart area to determine whether the captured images are in focus.The height of the
43、chart shall be (80 10) cm and the distance to the chart shall be adjusted in a way that the height of the image is in accord with the chart height.The surround areas should be filled with a reflective area of 18 % neutral grey. Prior to the measurement, the digital still camera shall be checked to s
44、ee if it correctly focuses on the chart. If not, the correct focus shall be obtained by changing the chart or the illumination condition. If different setup conditions are required when the focal length of the lens is extremely long or short, these setup conditions shall be reported together with th
45、e measurement results. ISO 2015 All rights reserved 3BS ISO 15781:2015ISO 15781:2015(E)Dimensions in millimetresFigure 2 Chart and positioning4.3 Battery statusA secondary battery should always be fully charged and a primary battery should always be a new one prior to performing the measurements in
46、order to avoid inconsistent measurements caused by varying power supply. For cameras that support an AC power supply, the AC power supply should be used.4.4 Memory cardFor digital still cameras that support connection to an external memory card, a card with a sufficient capacity that does not interf
47、ere with the test shall be used. The card shall be initialized and formatted in the camera. After formatting the card, it shall remain in the digital still camera.If the digital still camera only has the internal memory, all images should be deleted by initializing the memory prior to the measuremen
48、t.4.5 FlashIf the flash is used to perform the measurements, it shall be reported together with the results.5 Measurements5.1 Definition of measurement5.1.1 GeneralThis International Standard defines two measurement methods. The first method is the “external measurement” method which can be performe
49、d without disassembling the digital camera. The second method is the “internal measurement” method which requires the camera body to be partially disassembled in order to perform measurements using electrical signals inside the camera body. The first method is the preferred method for measurements made by users of digital cameras. The second method is the preferred method for measurements made by digital camera manufacturers.NOTE 1 Figure 3, Figure 4, and Figure 5 show the periods of time to be measured.NOTE 2
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