ISO 1230:1992
(Main)Photography — Determination of flash guide numbers
Photography — Determination of flash guide numbers
Specifies a method for measuring the reflector factor. Contains formulae for calculating the ISO guide number for flash lamps (with and without integral factors resp.). Gives terms and definitions.
Photographie — Détermination des nombres-guides des appareils à éclairs
Photography - Determination of flash guide numbers
General Information
Relations
Standards Content (Sample)
INTERNATIONAL
STANDARD
Second edition
1992-03-0 1
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.
Photography - Determination of flash guide
numbers
DGtermination des nombres-guides des appareils a
Photographie -
Mairs
-- --
--
Reference number
-- --
_-. __-_I_-- .-.--- ISO 1230:1992(E)
- . .
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ISO 1230:1992(E)
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. Esch 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, govern-
mental 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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an Inter-
national Standard requires approval by at least 75 % of the member
bodies casting a vote.
International Standard ISO 1230 was prepared by Technical Committee
ISO/TC 42, Photography.
This second edition cancels and replaces the first edition
(ISO 1230:1973), of which it constitutes a technical revision.
Annexes A, B and C of this International Standard are for information
only.
0 ISO 1992
All rights reserved. No part of this publication may be reproduced or utilized in any form
or by any means, electronie or mechanical, lncluding photocopying and microfilm, without
Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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ISO 1230:1992(E)
Introduction
In general flash photography, where the flash light Source is mounted
on a Camera, the product of the Camera lensjinumber and the distance
from the flash light Source to the subject is a constant with respect to the
ISO Speed of the film to be used. The illuminance of the subject varies
with the distance according to the inverse-Square law and, in Order to
obtain the Same suitable exposure on film, thej-number should be ad-
justed according to the Square root of the illuminance of the subject.
The constant is named “flash guide number” and is a very useful guide
for flash photographers, because the guide number represents, in a
sense, the power of illumination of the light Source, for both flash lamps
with and without integral reflectors and electronie flash equipment. The
Camera lens fnumber setting tan easily be calculated by dividing the
guide number by the distance from the flash light Source to the subject.
. . .
Ill
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INTERNATIONAL STANDARD ISO 1230:1992(E)
Photography -!- Determination of flash guide numbers
flash equipment compared to that from a bare lamp
1 Scope
in a direction perpendicular to the axis of the lamp.
This International Standard specifies the definition
3.2 guide number (GN): The product of the Camera
and determination of the ISO guide numbers of flash
lensfnumber required for a suitable exposure on a
light sources for general photographic use, including
film and the distance from the flash light Source to
expendable Photoflash lamps with and without inte-
the subject, in metres, with respect to the ISO Speed
gral reflectors and electronie flash equipment. DefL
of the film to be used.
nitions and measuring methods for the light output
of Photoflash lamps without integral reflectors are
3.3 ISO guide number (ISO/GN): The guide num-
specified in ISO 1229. Definitions and measuring
ber, expressed in metres, for a film of Speed ISO
methods for the light output of electronie flash
100/21”,
“X” synchronization, an exposure of 1/30 s
equipment are specified in ISO 2827.
and, in the case of an expendable Photoflash lamp
without integral reflector, a reflector factor of 5 (see
NOTE 1 The same technique may be used for
measurement of light output of Photoflash lamps with in- clause 5).
tegral reflectors.
4 Method for measurlng reflector factor
2 Normative references
4.1 Measurements of luminous intensity (in
candelas) shall be carried out in a room with non-
The following Standards contain provisions which,
reflecting Walls at a distance of at least 2 m or
through reference in this text, constitute provisions
twelve times the reflector diameter-, whichever value
of this International Standard. At the time of publi-
is the greater. For this purpose, normal Photoflash
cation, the editions indicated were valid. All stan-
dards are subject to revision, and Parties to lamps intended for equipment with reflectors shall
agreements based on this International Standard be used.
are encouraged to investigate the possibility of ap-
plying the most recent editions of the Standards in-
4.2 Sufficient quantities of Photoflash lamps shall
dicated below. Members of IEC and ISO maintain
be measured so as to ensure good average values;
registers of currently valid International Standards.
starting at the reflector axis, these measurements
shall be carried out in all directions of interest so
ISO 1229:1989, Photography - Expendable
that the reflector factor may be calculated.
photoflash lamps - Determination of light output.
5 Reflector factors for flash lamp
ISO 2827:1988, Phofography - Electronie flash
equipment - Determination of light output and per-
equlpment
formante.
If the reflector factor of any equipment for expend-
able Photoflash lamps otherwise complying with this
3 Definitions
International Standard differs materially from the
value 5, a correction factor shall be published by the
For the purposes of this International Standard, the
manufacturer of the equipment. This shall be
following definitions apply.
marked on the equipment or included as part of the
Standard instructions supplied with it, enabling the
3.1 reflector factor: The amplification of the lurni-
ISO guide number of the Photoflash lamp to be
nous intensity taking the beam intensity in a solid
transformed to a guide number for the combination
angle 2 x 5” around the axis of the reflector of the
of lamp and flash equipment.
-----------------
...
SLOVENSKI STANDARD
SIST ISO 1230:1997
01-september-1997
Photography - Determination of flash guide numbers
Photography -- Determination of flash guide numbers
Photographie -- Détermination des nombres-guides des appareils à éclairs
Ta slovenski standard je istoveten z: ISO 1230:1992
ICS:
37.040.10 Fotografska oprema. Photographic equipment.
Projektorji Projectors
SIST ISO 1230:1997 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 1230:1997
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SIST ISO 1230:1997
INTERNATIONAL
STANDARD
Second edition
1992-03-0 1
-----
~-- ~~------__-------
.
Photography - Determination of flash guide
numbers
DGtermination des nombres-guides des appareils a
Photographie -
Mairs
-- --
--
Reference number
-- --
_-. __-_I_-- .-.--- ISO 1230:1992(E)
- . .
---------------------- Page: 3 ----------------------
SIST ISO 1230:1997
ISO 1230:1992(E)
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. Esch 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, govern-
mental 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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an Inter-
national Standard requires approval by at least 75 % of the member
bodies casting a vote.
International Standard ISO 1230 was prepared by Technical Committee
ISO/TC 42, Photography.
This second edition cancels and replaces the first edition
(ISO 1230:1973), of which it constitutes a technical revision.
Annexes A, B and C of this International Standard are for information
only.
0 ISO 1992
All rights reserved. No part of this publication may be reproduced or utilized in any form
or by any means, electronie or mechanical, lncluding photocopying and microfilm, without
Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
---------------------- Page: 4 ----------------------
SIST ISO 1230:1997
ISO 1230:1992(E)
Introduction
In general flash photography, where the flash light Source is mounted
on a Camera, the product of the Camera lensjinumber and the distance
from the flash light Source to the subject is a constant with respect to the
ISO Speed of the film to be used. The illuminance of the subject varies
with the distance according to the inverse-Square law and, in Order to
obtain the Same suitable exposure on film, thej-number should be ad-
justed according to the Square root of the illuminance of the subject.
The constant is named “flash guide number” and is a very useful guide
for flash photographers, because the guide number represents, in a
sense, the power of illumination of the light Source, for both flash lamps
with and without integral reflectors and electronie flash equipment. The
Camera lens fnumber setting tan easily be calculated by dividing the
guide number by the distance from the flash light Source to the subject.
. . .
Ill
---------------------- Page: 5 ----------------------
SIST ISO 1230:1997
This page intentionally left blank
---------------------- Page: 6 ----------------------
SIST ISO 1230:1997
INTERNATIONAL STANDARD ISO 1230:1992(E)
Photography -!- Determination of flash guide numbers
flash equipment compared to that from a bare lamp
1 Scope
in a direction perpendicular to the axis of the lamp.
This International Standard specifies the definition
3.2 guide number (GN): The product of the Camera
and determination of the ISO guide numbers of flash
lensfnumber required for a suitable exposure on a
light sources for general photographic use, including
film and the distance from the flash light Source to
expendable Photoflash lamps with and without inte-
the subject, in metres, with respect to the ISO Speed
gral reflectors and electronie flash equipment. DefL
of the film to be used.
nitions and measuring methods for the light output
of Photoflash lamps without integral reflectors are
3.3 ISO guide number (ISO/GN): The guide num-
specified in ISO 1229. Definitions and measuring
ber, expressed in metres, for a film of Speed ISO
methods for the light output of electronie flash
100/21”,
“X” synchronization, an exposure of 1/30 s
equipment are specified in ISO 2827.
and, in the case of an expendable Photoflash lamp
without integral reflector, a reflector factor of 5 (see
NOTE 1 The same technique may be used for
measurement of light output of Photoflash lamps with in- clause 5).
tegral reflectors.
4 Method for measurlng reflector factor
2 Normative references
4.1 Measurements of luminous intensity (in
candelas) shall be carried out in a room with non-
The following Standards contain provisions which,
reflecting Walls at a distance of at least 2 m or
through reference in this text, constitute provisions
twelve times the reflector diameter-, whichever value
of this International Standard. At the time of publi-
is the greater. For this purpose, normal Photoflash
cation, the editions indicated were valid. All stan-
dards are subject to revision, and Parties to lamps intended for equipment with reflectors shall
agreements based on this International Standard be used.
are encouraged to investigate the possibility of ap-
plying the most recent editions of the Standards in-
4.2 Sufficient quantities of Photoflash lamps shall
dicated below. Members of IEC and ISO maintain
be measured so as to ensure good average values;
registers of currently valid International Standards.
starting at the reflector axis, these measurements
shall be carried out in all directions of interest so
ISO 1229:1989, Photography - Expendable
that the reflector factor may be calculated.
photoflash lamps - Determination of light output.
5 Reflector factors for flash lamp
ISO 2827:1988, Phofography - Electronie flash
equipment - Determination of light output and per-
equlpment
formante.
If the reflector factor of any equipment for expend-
able Photoflash lamps otherwise complying with this
3 Definitions
International Standard differs materially from the
value 5, a correcti
...
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