ISO 1230:2007
(Main)Photography — Determination of flash guide numbers for electronic flash equipment
Photography — Determination of flash guide numbers for electronic flash equipment
ISO 1230:2007 specifies the definition and determination of the ISO guide number of electronic flash equipment. It does not specify the definitions and measuring methods for the light output of electronic flash equipment, which are specified in ISO 2827.
Photographie — Détermination des nombres guides des appareils à éclairs
Fotografija – Določanje vodilnih števil za elektronski bliskovni pribor
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INTERNATIONAL ISO
STANDARD 1230
Third edition
2007-09-01
Photography — Determination of flash
guide numbers for electronic flash
equipment
Photographie — Détermination des nombres guides des appareils à
éclairs
Reference number
ISO 1230:2007(E)
©
ISO 2007
---------------------- Page: 1 ----------------------
ISO 1230:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2007 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 1230:2007(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. 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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 1230 was prepared by Technical Committee ISO/TC 42, Photography.
This third edition cancels and replaces the second edition (ISO 1230:1992), which has been technically
revised.
© ISO 2007 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 1230:2007(E)
Introduction
In general flash photography, where the flash light source is mounted on a camera, the product of the camera
lens ƒ-number and the distance from the flash light source to the subject is a constant with respect to the
ISO speed of the film or the digital still camera 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 or
image sensor, the ƒ-number is adjusted with respect 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 electronic flash equipment. The camera lens ƒ-number setting can easily be
calculated by dividing the guide number by the distance from the flash light source to the subject.
iv © ISO 2007 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 1230:2007(E)
Photography — Determination of flash guide numbers for
electronic flash equipment
1 Scope
This International Standard specifies the definition and determination of the ISO guide number of electronic
flash equipment. It does not specify the definitions and measuring methods for the light output of electronic
flash equipment, which are specified in ISO 2827.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
guide number
N
GN
product of the camera lens ƒ-number, required for a suitable exposure on a film or an image sensor, and the
distance from the flash light source to the subject with respect to the ISO speed of the film or the digital still
camera to be used
NOTE The guide number is expressed in metres. Annex A provides the conversion calculation for converting the
guide number from metres into feet.
2.2
ISO guide number
N
ISO/GN
guide number, for a film or a digital still camera of ISO 100, “X ” synchronization and an exposure time which
can fully utilize the total output of the flash light source
3 Calculation of the guide number
3.1 ISO guide number
The ISO guide number, N , shall be calculated using the following formula:
ISO/GN
Nk=I()t dt (1)
ISO/GN
∫
where
–1 2 –1
k is a constant equal to 0,51 lm ⋅m⋅s ;
∫I(t)dt is the time integral of the luminous intensity of electronic flash equipment, expressed in candella
–1
seconds (cd⋅s = lm⋅sr ⋅s).
See Annex B for details of Equation (1).
© ISO 2007 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 1230:2007(E)
3.2 Guide number for any ISO speed other than 100
The guide number for any ISO speed other than 100 can be calculated from the following formula:
S
NN(ISO,S) =× (2)
ISO/GN
100
where S is the ISO speed (arithmetic).
4 Designation of guide number
Designation of guide numbers on products or instructions should be rounded to two significant digits and
followed by metres. When a guide number does not express the ISO guide number [i.e. for films or digital still
cameras other than those of ISO speed 100 (arithmetic)], the refere
...
SLOVENSKI STANDARD
SIST ISO 1230:2008
01-januar-2008
)RWRJUDILMD±'RORþDQMHYRGLOQLKãWHYLO]DHOHNWURQVNLEOLVNRYQLSULERU
Photography - Determination of flash guide numbers for electronic flash equipment
Ta slovenski standard je istoveten z:
ICS:
37.040.10 Fotografska oprema. Photographic equipment.
Projektorji Projectors
SIST ISO 1230:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
INTERNATIONAL ISO
STANDARD 1230
Third edition
2007-09-01
Photography — Determination of flash
guide numbers for electronic flash
equipment
Photographie — Détermination des nombres guides des appareils à
éclairs
Reference number
ISO 1230:2007(E)
©
ISO 2007
---------------------- Page: 2 ----------------------
ISO 1230:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2007 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 1230:2007(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. 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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 1230 was prepared by Technical Committee ISO/TC 42, Photography.
This third edition cancels and replaces the second edition (ISO 1230:1992), which has been technically
revised.
© ISO 2007 – All rights reserved iii
---------------------- Page: 4 ----------------------
ISO 1230:2007(E)
Introduction
In general flash photography, where the flash light source is mounted on a camera, the product of the camera
lens ƒ-number and the distance from the flash light source to the subject is a constant with respect to the
ISO speed of the film or the digital still camera 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 or
image sensor, the ƒ-number is adjusted with respect 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 electronic flash equipment. The camera lens ƒ-number setting can easily be
calculated by dividing the guide number by the distance from the flash light source to the subject.
iv © ISO 2007 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 1230:2007(E)
Photography — Determination of flash guide numbers for
electronic flash equipment
1 Scope
This International Standard specifies the definition and determination of the ISO guide number of electronic
flash equipment. It does not specify the definitions and measuring methods for the light output of electronic
flash equipment, which are specified in ISO 2827.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
guide number
N
GN
product of the camera lens ƒ-number, required for a suitable exposure on a film or an image sensor, and the
distance from the flash light source to the subject with respect to the ISO speed of the film or the digital still
camera to be used
NOTE The guide number is expressed in metres. Annex A provides the conversion calculation for converting the
guide number from metres into feet.
2.2
ISO guide number
N
ISO/GN
guide number, for a film or a digital still camera of ISO 100, “X ” synchronization and an exposure time which
can fully utilize the total output of the flash light source
3 Calculation of the guide number
3.1 ISO guide number
The ISO guide number, N , shall be calculated using the following formula:
ISO/GN
Nk=I()t dt (1)
ISO/GN
∫
where
–1 2 –1
k is a constant equal to 0,51 lm ⋅m⋅s ;
∫I(t)dt is the time integral of the luminous intensity of electronic flash equipment, expressed in candella
–1
seconds (cd⋅s = lm⋅sr ⋅s).
See Annex B for details of Equation (1).
© ISO 2007 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 1230:2007(E)
3.2 Guide number for any ISO speed other than 100
The guide number for any ISO speed other than 100 can be calculated from the following formula:
S
NN(ISO,S) =× (2)
ISO/GN
100
where S is the ISO s
...
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