ISO 15781:2019
(Main)Photography — Digital still cameras — Measuring shooting time lag, shutter release time lag, shooting rate, and start-up time lag
Photography — Digital still cameras — Measuring shooting time lag, shutter release time lag, shooting rate, and start-up time lag
This document specifies how to measure and report the shooting time lag, shutter release time lag, shooting rate and start-up time lag 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 that determines the timing values without requiring access to the inside of the digital still camera. This document does not address the measurement either of auto focus speed below recommended illumination level or auto focus accuracy.
Photographie — Caméras numériques — Décalage dans le temps du mesurage de la prise, décalage dans le temps de l'ouverture de l'objectif, cadence de prise et temps de démarrage
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 15781
Third edition
2019-06
Photography — Digital still cameras —
Measuring shooting time lag, shutter
release time lag, shooting rate, and
start-up time lag
Photographie — Caméras numériques — Décalage dans le temps du
mesurage de la prise, décalage dans le temps de l'ouverture de
l'objectif, cadence de prise et temps de démarrage
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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 written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test conditions . 3
4.1 Illumination of the test scene . 3
4.2 The chart and positioning of the digital still camera . 4
4.3 Battery status . 5
4.4 Memory card . 5
4.5 Flash . 5
4.6 Image stabilization . 5
4.7 Other camera settings . 5
5 Measurements . 6
5.1 Definition of measurement. 6
5.1.1 General. 6
5.1.2 Measurement with external controls . 7
5.1.3 Measurement with internal controls . 7
5.2 Measurement method . 8
5.2.1 Start-up time . 8
5.2.2 Shooting time lag . 9
5.2.3 Shutter release time lag .10
5.2.4 Shooting rate .10
6 Reporting the results .11
Annex A (informative) Test results of methods to start the timing device .13
Annex B (informative) Timing device .15
Annex C (informative) Measurement with internal controls .21
Annex D (informative) Examples of reporting the result .28
Annex E (informative) Estimation of the measurement accuracy .30
Annex F (informative) Example setup for measuring the shooting time lag for cameras with
continuous autofocus.32
Bibliography .36
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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee 42, Photography.
This third edition cancels and replaces the second edition (ISO 15781:2015), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Current scope includes digital still cameras that continuously shoot images into the buffer and select
an image depending on the moment the exposure button is pressed.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
Introduction
Taking pictures of a moving target was nearly 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 focus,
another part is needed to adjust the exposure, etc. This unwelcome but unavoidable period of time
is called shooting time lag. This is often mixed with the term shutter release time lag, which is also
defined in this document. Optimized systems are nowadays able to decrease 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 fast image processing within the
digital still camera that can be measured according to the method described in this document.
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 lag is therefore another important value, which can be determined using
this document.
INTERNATIONAL STANDARD ISO 15781:2019(E)
Photography — Digital still cameras — Measuring shooting
time lag, shutter release time lag, shooting rate, and start-
up time lag
1 Scope
This document specifies how to measure and report the shooting time lag, shutter release time lag,
shooting rate and start-up time lag 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 that
determines the timing values without requiring access to the inside of the digital still camera.
This document does not address the measurement either of auto focus speed below recommended
illumination level or auto focus accuracy.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 7589, Photography — Illuminants for sensitometry — Specifications for daylight, incandescent
tungsten and printer
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
digital still camera
device which incorporates an image sensor and produces a digital signal representing a still picture (1)
Note 1 to entry: A digital still camera is typically a portable, hand-held device. The digital signal is usually
recorded on a removable memory, such as a solid-state memory card or magnetic disk.
[SOURCE: ISO 12231, 3.40, modified — Note 2 to entry has been deleted.]
3.2
shooting time lag
t
SL
time elapsed from stand-by state to reaching capture point on a digital still camera or a module built
into a mobile device and the beginning of the exposure
Note 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 prior to the beginning of the exposure.
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. determination of the exposure and focus adjustment. The time
needed for these procedures is part of the shooting time lag.
Note 3 to entry: A capture point is often initiated from stand-by state by firmly depressing the shutter button to
the maximum extent without introducing a discontinuity, see 3.8.
3.3
shutter release time lag
t
RL
time elapsed from pre-capture point (3.7) to the time of starting the exposure by reaching capture
point after having stabilized the focus operation (often due to half pressing of the shutter button), in
the case of digital still cameras that distinguish between pre-capture and capture points (3.8) (often the
half pressing and the fully pressing of the shutter button)
Note 1 to entry: Instead of shutter release time lag, the terms shutter lag and release lag are used in some
publications.
Note 2 to entry: A capture point is often initiated from pre-capture point by fully pressing down the shutter button.
3.4
start-up time lag
t
start-up
time elapsed between switching a digital still camera on and the moment the camera has reached a
standby state (3.6) ready to shoot
Note 1 to entry: Start-up time lag excludes the initialization of a memory card.
Note 2 to entry: How this time is determined for the different devices is described in 5.2.1.
3.5
shooting rate
f
shooting
reciprocal of the time elapsed between the beginning of the exposure of an image until the beginning of
the exposure of the next image, that is, between successive capture start states
3.6
standby state
state achieved following the power-up process, in which a digital still camera is powered on and ready
to capture an image
Note 1 to entry: If the digital still camera uses an electronic viewfinder, a preview image is normally displayed
during the standby state.
Note 2 to entry: Standby state excludes the initialization of a memory card.
3.7
pre-capture point
position of a user control of a digital still camera which activates pre-capture processes, such as auto-
focus and exposure calculation
Note 1 to entry: The pre-capture point is typically reached by pressing an exposure button roughly halfway
down on traditional digital still camera. On mobile devices with touchscreen this point might be reached by long
pressing the trigger button.
3.8
capture point
position of a user control of a digital still camera which activates the image capture operation
Note 1 to entry: The capture point is typically reached by fully depressing the exposure button on traditional
digital still cameras. On mobile devices with touchscreen this point can be reached either when pushing the
trigger button, or releasing it.
2 © ISO 2019 – All rights reserved
3.9
push duration
total elapsed time during which the trigger button is pushed
Note 1 to entry: This duration is not usually associated with a particular function on traditional digital still
camera other than capture burst. On mobile devices that use a touchscreen, it can trigger some particular
functions such as the autofocus.
4 Test conditions
4.1 Illumination of the test scene
An illumination level between 500 lx to 5 000 lx is recommended. Special measurement purposes may
require other levels.
The test scene shall be illuminated in a way that avoids specular reflection (see Figure 1). This can be
achieved by using a geometry typical for reproduction photography, which means positioning the light
sources in approximately a 45° angle to the surface of the chart. 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 is an acceptable match to the daylight illuminant, shall be
conducted in accordance with ISO 7589.
Key
1 calibrated spectral photometer
2 test chart
3 light source tungsten or filtered to D55
Figure 1 — Principle for illuminating the target
4.2 The chart and positioning of the digital still camera
The digital still camera 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 a 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 include a black-and-white
checker board or the three-line chart shown in informative Annex B. If the above condition is met, a
typical image assessment chart may be used. Also, the ISO 12233 resolution chart may be placed in the
chart area to determine whether the captured images are in focus.
The height of the 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 see 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 the measurement results.
4 © ISO 2019 – All rights reserved
Key
1 surround area: 18% grey chart
2 chart height 800 mm
3 chart
4 33 x focal length
5 focal length
6 image height
Figure 2 — Chart and positioning
4.3 Battery status
A secondary battery should always be fully charged and a primary battery should always be a new one
prior to performing the measurements in 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 card
For digital still cameras that support connection to a removable memory card, a card with a sufficient
capacity and speed so that it does not interfere with the test shall be used. Slow cards can interfere
with the measurements and increase the measured times. 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 internal memory, all images should be deleted and sufficient memory
should be free that any lack of memory does not interfere with the test.
4.5 Flash
If the flash is used to perform the measurements, it shall be reported together with the results.
4.6 Image stabilization
In case the image stabilization is used to perform the measurement, it shall be reported together with
the results.
4.7 Other camera settings
Since camera settings can impact the measurement results the factory settings of the camera shall be
used and any deviation from those shall be reported with the measurement results.
5 Measurements
5.1 Definition of measurement
5.1.1 General
This document defines two measurement methods. The first method is the “external measurement”
method, which can be performed 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 Figures 3, 4, and 5 show the periods of time to be measured.
NOTE 2 “Procedure related to the pre-capture point” means the procedure by which the digital still camera
measures the light intensity and distance, determines the exposure, and adjusts the focus when the pre-capture
point switch of the digital still camera is pressed.
NOTE 3 “Procedure related to the capture point” means the procedure by which the digital still camera
processes the image captures and preparation of the image storage when the capture point switch of the camera
is pressed.
a
The time between switching the power on and the moment the viewfinder image (through-image)
is displayed, or the time between switching the power on and the moment pre-capture point can be
accepted, whichever is longer.
Figure 3 — Measurement period for start-up time lag
6 © ISO 2019 – All rights reserved
Figure 4 — Measurement period for shooting time lag and shutter release time lag
Figure 5 — Measurement period for shooting rate
5.1.2 Measurement with external controls
The measurement with external controls is performed without disassembling the camera with the
advantage that the measurement can be performed on the product level. Specifically, for instance,
the measurement can be performed shooting a timing device that can determine a time interval from
captured images. An example of this method is shown in informative Annex B.
When using the measurement with external controls the acceptable level of the time lag between
pressing the exposure button and activating the timing device is application dependent and needs
to be considered prior to performing a test and the estimated error caused by this time lag shall be
reported together with the results (see Annex B). A test was performed using different approaches and
the results are shown in Annex A.
5.1.3 Measurement with internal controls
The measurement using internal controls and connectors enables a direct measurement of time
intervals between input signals and device control signals but it involves disassembling the camera.
This allows the operational timing to be obtained reliably and has the advantage that the measurement
can be performed accurately and stably. With this method, there is no bias due to the accuracy of the
actuation device (see Annex B).
However, only camera manufacturers usually use this method because it is very difficult for parties
other than camera manufacturers to disassemble the camera and select and measure the device control
signals. An example of this method is shown in Annex C.
5.2 Measurement method
5.2.1 Start-up time
The digital still camera shall be switched on and set to record mode. Every setting that requires
additional time when switching the camera on (e.g. playing an intro sound) shall be turned off, and the
camera shall be focused on the timing device before it is switched off again. Start the measurement
when the power switch is turned on again. The measurement value shall be an average of at least
10 measurements.
In cases of devices that include other applications besides the camera (mobile devices) the devices
shall be switched off completely prior to the measurement and switched on again to make sure all
applications running on the device have been terminated. The power switch for turning the camera on
may be substituted by starting a camera app or pressing an activation key. In these cases, the fastest
method of starting the camera shall be selected and be reported together with the results.
For these devices the starting point for turning the camera function on is the regular operational
standby mode of the device. This means the device is in standby and locked. If it is necessary to unlock
the mobile device and to enter one or multiple menus to start the camera module, this time shall be
integrated in the reported start-up time lag.
The digital still camera shall not be disconnected from the power supply until the test is finished. The
measurement results and conditions shall be reported according to the description in Clause 6.
When using the measurement with external controls, the timing device shall be inserted electronically
to control the power switch or the power supply of the camera, if possible. The accuracy of the timing
device for measuring the start-up time shall be at least 0,1 s (the sampling shall be 0,01 s). If the timing
device is started manually all measured values <0,5 s shall be reported as 0,5 s and the fact of the
manual activation shall be reported together with the result. When the power switch is turned on,
the timing device shall be started. A picture of the chart (object) shall be taken immediately after the
shutter release becomes active after turning the camera on.
The start-up time lag is obtained through the Formula (1).
tt=−t (1)
S0 SL
where
t is start-up time lag;
S
t is time elapsed from operating the switch until the beginning of the exposure of the first image;
t is shooting time lag.
SL
When using the measurement with internal controls, suppliers as shown in Annex C shall directly
observe appropriate signals, and the time defined in 5.1.1 shall be measured.
NOTE The shooting time lag t needs to be measured before applying Formula (1) to determine the start-up
SL
time lag t .
S
8 © ISO 2019 – All rights reserved
5.2.2 Shooting time lag
5.2.2.1 General
Continuous autofocus of the camera shall be switched off if possible. In case that is possible follow
procedure described in 5.2.2.2. If that is not possible follow procedure described in 5.2.2.3. For
digital still cameras that continuously shoot images into a buffer, exposure time has an influence on
the shooting time lag measurement since the exposure point depends on the exposure time. Annex E
provides more details on this issue.
Exposure time shall be reported.
5.2.2.2 Measurement in case of normal autofocus
Prior to each measurement of the shooting time lag, the digital still camera shall be defocused by either:
a) turning to face a distant object that shall be located at a distance of at least 100 times the focal
length of the camera lens or 5 m, whichever is greater;
b) manually focused to infinity;
c) focused to infinity using a collimator.
The shooting time lag, t , shall be measured by turning the digital still camera to face the chart and by
SL
fully pressing the exposure button.
In the case of the measurement with external controls, the shooting time lag is obtained by comparing
the state of the timing device at the moment the exposure button is fully pressed and the state of the
timing device in the correct focused image. If the image is clearly out of focus, it shall not be used
to measure the shooting time lag because in this case the camera may trade the focus accuracy for
higher speed (shutter priority) and the image of the timing device is blurred and unable to show the
correct timing. For cameras that do not deliver sharp images when pressing the exposure button fully,
the digital still camera shall be allowed to focus by first pressing the exposure button halfway down;
immediately after the camera indicates that it is in focus, the exposure button shall be fully pressed.
The state of the timing device shall be recorded when the exposure button is pressed halfway down
and the fact that the digital still camera did not focus correctly without this manual adjustment shall be
reported together with the results.
In the case of the measurement with internal controls, appropriate signals shall be directly observed as
shown in Annex C, and the time period defined in 5.1.1 shall be measured.
The reported shooting time lag shall be an average of at least 10 measurements shot in a row (with the
camera defocused between each shot) right after the previous image has been stored to the storage
media and without switching the camera off. Depending on the required measurement accuracy,
additional measurements might be necessary as shown in Annex E.
If the measured time is significantly shorter or longer for the first of the 10 images, the measurement
shall be repeated. If the same results occur, values for the first and the following exposures shall be
reported separately.
The measured shooting time lag will vary depending on the focal length the camera is set to.
The measurement results and conditions shall be reported according to the description in Clause 6.
5.2.2.3 Measurement in case of continuous autofocus
It is necessary to take into account the time the continuous autofocus requires to focus on the chart
before the capture point.
To ensure consistent and repeatable results the camera needs to focus on a close distance “defocus
chart” prior to focusing on the test chart. This “defocus chart” shall be placed in the optical path at
a minimum distance of 150 mm from the camera or to the shortest distance the camera can focus on
whichever is longer. The “defocus chart” shall consist of high contrast structures on which the camera
can easily focus. A dead leaves target (See ISO TS 19567-2) with a contrast of 50 % and greater is one
potential chart. The “defocus chart” shall be illuminated with a light source that delivers a spectral
distribution comparable to the one for the illumination of the test chart and at an illumination level that
is within ±0,3 exposure values of the one for the test chart. This avoids a readjustment of the auto white
balance and auto exposure setting for the final image.
In the case the above procedure is not applicable (e.g. measuring in macro mode) the defocus chart and
the test chart can be switched so that the defocus is done on a longer distance and the focus on the test
chart on a short distance. This specific case needs to be reported with the results.
The defocus chart shall be extracted out of the optical path in 0,1 s or less. This can be done by
mechanically moving the “defocus chart” or by using a mirror or turning the camera. However it needs
to be made clear that no vibrations occur that influence the results. In special occasions setups may be
used where the extraction of the defocus target takes longer than the 0,1 s. These setups are optional
and measurements made with those shall clearly be marked in the results.
The moment the defocus target is out of the optical path is the time 0. The timing device itself may be
started at a defined time prior to the process to be able to measure negative shooting time lags. For
cameras with focus priority the exposure shall be triggered at time 0. For cameras with shutter priority
exposure, shooting time lag shall be measured as the shortest delay from time 0 that ensures to give
not more than 20 % of the images that are obviously out of focus. This delay shall be introduced by
increasing the time between time 0 and the pressing of the exposure button from 0 with accuracy of
0,01 s with no less than 30 shots.
Annex F is one out of many potential setups how the measurement may be performed in case of
continuous autofocus.
That the device is using continuous autofocus shall be reported.
The reported shooting time lag shall be an average of at least 10 measurements shot in a row right after
the previous image has been stored to the storage media and without switching the camera off. As
specified above, the camera shall be defocused using the “defocus chart” in between each measurement.
Depending on the required measurement accuracy, additional measurements might be necessary as
shown in Annex E.
If the measured time is significantly shorter or longer for the first of the 10 images, the measurement
shall be repeated. If the same results occur, values for the first and the following exposures shall be
reported separately.
The measurement results and conditions shall be reported according to the description in Clause 6.
5.2.3 Shutter release time lag
The shutter release time lag shall be measured using the same requirements for the shooting time lag
except that the state of timing device shall be recorded after the digital still camera is facing the chart
(object) and is in focus.
For digital still cameras that continuously shoot images into a buffer, exposure time has an influence
on the shutter release time lag measurement since the exposure point depends on the exposure time.
Annex E provides more details on this issue.
The measurement results and conditions shall be reported according to the description in Clause 6.
5.2.4 Shooting rate
The default setting for measuring the shooting rate should be the camera set to the highest pixel count
available in the camera and the highest image quality for compressed and fully processed images (e.g.
lowest JPEG compression) available. However, any other setting may be used and the setting shall be
10 © ISO 2019 – All rights reserved
reported along with the measurement results. The camera shall be positioned as described in 4.2 and
correctly focused on the target. To achieve the highest frequency possible, the digital still camera shall
be set to burst mode (if it exists), and the exposure time shall be 1/100 of a second or less (if adjustable).
If the camera does not allow setting mode and exposure time, the measurement shall be performed
using the default setting.
A set of the images should be taken with the camera by keeping the exposure button pressed until
the shooting rate slows significantly down or until 100 images are captured whichever number is
smaller. The reciprocal of the time elapsed from the beginning of the exposure for one image and the
beginning of the exposure of the next image is the value of the shooting rate. If the shooting rate changes
significantly during the test, the number of exposures possible at the used mode shall be reported along
with the value of the shooting rate.
NOTE Digital still cameras often shoot several images at a constant frequency at the beginning of capturing
a series of images. In case the buffer memory fills up because the camera is not able to process and transfer the
images to the storage medium fast enough, the frequency decreases after the memory is full. This is the point
where the camera noticeably slows down.
The shooting rate shall be calculated on a specified number of frames, at least 10. If either of the
following events takes place prior to 10 frames, the number of frames actually taken shall be recorded
and reported:
a) The camera ceases to function for more than 2 s — effectively rendering multiple exposure mode
useless, or
b) The frame rate slows significantly and the camera indicates that its internal buffer is full.
The frame rate shall be determined using the Formulae (2) and (3):
n
1 1
f = with T = ()tt− (2)
ni i−1
∑
T n−1
n
i=2
n
s= ((tt−−))T (3)
∑ ii−1 n
n−1
i=2
where
f is image frequency;
n is the number of the last image before the camera begins to slow down;
t is the time from the start until the beginning of the exposure for a specific image;
T is the arithmetic mean of the measured value for n intervals from the beginning of the exposure
n
for one image until the beginning of the exposure for the next image;
s standard deviation.
The shooting rate, the standard deviation of the mean, and measurement conditions shall be reported
according to the description in Clause 6.
6 Reporting the results
The results of the timing values described in this document depend on several camera settings as well
as surrounding conditions. These camera settings and surrounding conditions shall be managed enough
during the measurement and they shall be reported with the results. In some cases, however, simpler
presentation without complete description on the camera settings or the surrounding conditions may
be used. An example is specification notes in a catalogue for the end users. In this case the missing
information should be accessible and in the public domain.
The results of measurements should be reported with at least two significant digits. When the shooting
time lag and start-up time lag is less than one second, the shutter release time lag is less than 10 ms or the
shooting rate is less than one image per second, the results may be reported with one significant digit.
With respect to the reporting of the shutter release time lag:
If either of the maximum or minimum value according to the measurement method in 5.2.3 is shifted
from the average value (20 ms or more), maximum and minimum values shall also be reported in
addition to the average value.
A complete report of the results shall contain all the necessary information in order to reproduce the
measurement.
Small letters indicate for the measurements for which the reporting of these settings are mandatory,
if not all: for shooting time lag, for shutter release time lag, for start-up time lag and for
(a) (b) (c) (d)
shooting rate.
In particular, the following shall be recorded:
— measurement method used;
— exposure time for digital still cameras that continuously shoot images into a buffer ;
(a,b)
— the push time for devices for which the push duration might trigger some particular functions ;
(a, b)
— identification of the measured product, e.g. product type, serial number, firmware version,
information on the used lens;
— identification of the used memory card, e.g. card specifications, memory size ;
(c, d)
— any special environmental conditions in which the test was performed, e.g. illumination of the test
scene, subject distance, special setup conditions ;
(a, b, d)
— any specific conditions necessary to enable the test to be performed, e.g. power supply;
— any operating states of the camera necessary to enable the test to be performed, e.g. exposure time,
number of recorded pixels, image quality, capture mode (e.g. portrait, sports), focal length, focus
mode (e.g. high speed), flash usage, stabilization ;
(a, b, d)
— In case of reporting the measurement result of continuous autofocus, indication that this is the
result of continuous autofocus and the distance of “defocus chart” ;
(a)
— In case of shutter priority, the ratio of images are obviously out of focus unless the ratio is 0 ;
(a)
— In case of devices that include other applications the method of activating the camera .
(c)
Camera settings and surrounding conditions shall be maintained during measurements and reported
with the results.
An example of a test report with information to report and associated values are given in Annex D.
12 © ISO 2019 – All rights reserved
Annex A
(informative)
Test results of methods to start the timing device
To find out about the time lag between the actuation of the timing device and the closure of the exposure
switch (activated by the exposure button) of the digital still camera, an experiment has been performed
using several real cameras (see Figure A.1).
A modified version of the timing device mentioned in B.2. has been used. This version used one input for
the micro switch to start the device and a second input that was connected to the exposure button of
the sample camera as a stop signal. This way the time lag between the two signals could be measured.
A positive value in Table A.1 means that the micro switch was actuated before the camera exposure
switch. A negative value means that the force needed for the micro switch was higher than that needed
for the camera, which leads to the case that the camera was actuated before the micro switch.
Table A.1 — Measured times lags between actuation of the micro switch and the camera
exposure switch
Activating Camera 1 Camera 1 Camera 2 Camera 2 Camera 3 Camera 3
force index finger electromagnetic index finger electromagnetic index finger electromagnetic
needed finger finger finger
for micro
switch
N ms ms ms ms ms ms
1,2 8 0,8 27 1,5 8 1
1,6 3 0,35 35 1,1 17 1,4
1,8 −3 1,25 21 1,7 3 2
3 −9 0,75 −2,5 1 −22 −2,5
4,2 −25 −11 −30 −27 −25 −7
Key
X activation force [N]
Y time lag [mSec.]
camera 1 index finger
camera 1 electromagnetic finger
camera 2 index finger
camera 2 electromagnetic finger
camera 3 index finger
camera 3 electromagnetic finger
NOTE Solid lines show the results from the index finger and the dashed lines the results from the
electromagnetic finger.
Figure A.1 — Time lag
The experiment shows that for using the index finger it is important to select a micro switch that
has about the same activating force as the camera exposure button if a time lag smaller than 10 ms
is needed. Using an average switch, the time lag is typically within the area of 30 ms. Therefore, the
assigned accuracy of the measurement using the index finger to actuate a micro switch is ±30 ms.
For the “electromagnetic finger” the results show that as long as the force needed to actuate the
micro switch is smaller than the force needed to actuate the camera exposure button, the time lag is
within ±2 ms. Only if the force needed to actuate the micro switch is much higher than the one needed
to actuate the exposure button, the time lag is significantly higher. Therefore the assigned accuracy for
the measurement using the electromagnetic finger is ±2 ms.
14 © ISO 2019 – All rights reserved
Annex B
(informative)
Timing device
B.1 Actuation of the timing device
This document notes four different ways to actuate the timing device that is needed to perform the
described measurements. The first two ways have been evaluated (see informative Annex A for details)
and, based on the results, been given a related deviation. The term deviation in this case describes the
time lag between the actuation of the timing device and the closure of the exposure switch of the camera.
When an actuation method is used, it is a good practice to determine and report its statistical accuracy
(mean and standard deviation). If a switch is used, it is also good practice to report the activating force.
Index finger: starting the timing device using a micro switch that is activated by the tester's index
finger (see Figure B.1). Although a carefully selected switch in combination with an experienced tester
may lead to higher accuracies the typical accuracy is ±0,03 s. The typical activating force for a camera
exposure button is between 1,0°N and 3,0 N. If a micro switch is used
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...