ISO 15781:2019

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
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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
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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).
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.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 pres
...