ISO 516:2019

INTERNATIONAL ISO
STANDARD 516
Fourth edition
2019-04
Camera shutters — Timing — General
definition and mechanical shutter
measurements
Obturateurs d'appareils photographiques — Durée d'exposition —
Définition générale et mesurages d'obturateur mécanique
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 Symbols . 4
5 Required characteristics and their tolerances . 5
5.1 Exposure time . 5
5.1.1 Exposure time marking . 6
5.1.2 Tolerances . 6
5.2 Delay time . 6
5.2.1 Front shutters . 6
5.2.2 Focal-plane shutters . 8
6 Test methods . 9
6.1 General . 9
6.2 Apparatus . 9
6.2.1 Apparatus . 9
6.2.2 Detector . 9
6.2.3 Time-interval meter .10
6.3 Front-shutter test .10
6.3.1 Test assembly .10
6.3.2 Procedure .10
6.4 Focal-plane-shutter test .11
6.4.1 Test assembly .11
6.4.2 Procedure .12
7 Explanatory notes .13
7.1 Tolerance .13
7.2 Test method .14
Annex A (normative) Graphic test methods .15
Bibliography .22
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
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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 ISO/TC 42, Photography.
This fourth edition cancels and replaces the third edition (ISO 516:1999) which has been technically
revised. The following changes have been made:
— The title and scope have been updated to reflect that the document is applicable to mechanical
shutters.
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
A superseded edition of this document was developed in the mechanical-shutters-only era. The scope
of this edition has been changed as many digital still cameras with non-mechanical shutters are now
introduced to the market.
INTERNATIONAL STANDARD ISO 516:2019(E)
Camera shutters — Timing — General definition and
mechanical shutter measurements
1 Scope
This document provides a uniform basis for determining the exposure times for all types of shutters
used in still cameras and contains suitable definitions of the terms used.
It specifies the exposure-time markings for all types of shutters and their tolerances.
The characteristics of all types of mechanical shutters, which are mounted in still cameras and affect
the control of exposure, motion-stopping ability and synchronization with a photoflash light source are
also defined.
The tolerances specified are the target values for the shutter performance that can be expected to
give good results. They are not intended for application as a general inspection standard in controlling
the performance of mechanical shutters, since tolerances may vary with the feature and price class of
camera tested.
Test methods are described for routine manufacturing testing and quality control. These test methods
require access to the focal plane of the camera and can therefore not be applied to assembled digital
still cameras.
2 Normative references
There are no normative references in this document.
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
front shutter
any shutter in the vicinity of the lens
Note 1 to entry: The front shutter can be in front of, behind or between the lens elements and can consist of
rotating discs, rotating slats, sliding blades, oscillating blades, etc. Programmed shutters are also included.
Note 2 to entry: The common characteristic for the front shutter is that the entire picture area is exposed almost
simultaneously.
Note 3 to entry: When the shutter and diaphragm are located too far apart, both exposure and shutter speed may
vary at different points in the picture area.
3.2
focal-plane shutter
any shutter in the vicinity of the focal plane
Note 1 to entry: The focal-plane shutter can consist of fixed or variable slit curtains, rotating discs, sliding
blades, etc.
Note 2 to entry: The essential feature of the focal-plane shutter is that the picture area is exposed incrementally,
in such a way that the time required to expose the entire picture area is greater than the exposure time of any
one point.
3.3
effective time
t
e
best measure of the amount of light falling on the picture area
Note 1 to entry: Effective time is defined by the following formula:
H
t =
e
E
Note 2 to entry: At any point on the picture area, t is generally the same for the entire picture area for front
e
shutters when vignetting is not severe. For focal-plane shutters, t will vary with w and v . The formula in Note 1
e c
to entry can be approximated with the below formula for convenience in measurement:
w
t = (focal plane shutter)
e
v
c
The formula in Note 2 to entry can only be applied under the condition of w ≥ d /A.
s
3.4
exposure time
t
eo
effective time measured at the centre of the picture area
3.5
total time
t
o
the time for which any given point in the picture area is exposed to light
Note 1 to entry: At any point on the picture area, to is generally the same, or almost, on the entire picture area for
front shutters.
Note 2 to entry: For a focal-plane shutter, however, to is dependent on w, A, d and V . The curtain displacement to
s c
completely expose one point becomes w + d /A, which can be converted to t , if the velocity is known, using the
s o
following formula:
d
s
w+
A
t =
o
V
c
Note 3 to entry: This formula can be inexact in the presence of vignetting.
See Figure 1.
2 © ISO 2019 – All rights reserved

a
Taking lens.
b
Curtain.
c
Focal lens.
Figure 1 — Total time for a focal-plane shutter
3.6
shutter efficiency
η
ratio of effective time to total time
Note 1 to entry: The shutter efficiency is given by:
t
e
η=
t
o
3.7
fluctuation of exposure time
p
the value of p is determined by the following formula
x +σ
p
2 =
x −σ
where x and σ are the mean and standard deviation of the values of five successive measurements
3.8
ratio of two adjacent exposure times
q
ratio of the mean values of two adjacent shutter speed settings obtained from values of five successive
measurements
Note 1 to entry: The ratio is expressed by the following formula:
...