ISO 8478:1996
(Main)Photography — Camera lenses — Measurement of ISO spectral transmittance
Photography — Camera lenses — Measurement of ISO spectral transmittance
Gives a method for measuring the spectral transmittance of camera lenses. Describes particular conditions for measuring the axial spectral transmittance over a wavelength range from 350 nm to 700 nm of camera lenses which are to be used mainly for taking pictures of very distant objects.
Photographie — Objectifs photographiques — Mesurage du facteur spectral de transmission ISO
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Standards Content (Sample)
INTERNATIONAL
STANDARD 8478
First edition
1996-12-01
Photography - Camera lenses -
Measurement of IS0 spectral
transmittance
Objectifs photographiques - Mesurage du facteur
Photographie -
spectral de transmission IS0
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Refer-en& number
IS0 8478:1996(E)
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Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) 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 International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 8478 was prepared by Technical Committee
ISO/TC 42, Photography.
Annex A forms an integral part of this International Standard.
0 IS0 1996
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 mechanrcal, including
photocopyrng and mrcrofilm, without permlssion In writing from the publisher.
lnternational Organization for Standardization
Case Postale 56 l W-1 211 Geneve 20 l Swrtzerland
Printed in Switzerland
ii
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@ IS0 IS0 8478: 1996(E)
Introduction
This International Standard describes a preferred method for the
measurement of spectral transmittance. Alternative methods may be used
provided that the method gives the same result as that obtained according
to this International Standard within the tolerances allowed by it. In the
case of lenses with very long or short focal lengths, and in large aperture
lenses, care should be taken to maintain the ideal integration properties of
the integrating sphere.
Spectral transmittance of the lens under test may vary with the diameter
of the incident beam and with the angle of incidence of the beam. In order
to obtain uniform results, this International Standard specifies that the
measurement is to be made with a collimated beam incident upon the lens
along its optical axis, and filling the central half diameter of its entrance
pupil at its minimumf-number.
In the case of lenses with very long or short focal lengths, the measuring
method specified in this International Standard may not be applicable due
to the difficulty in preparing a very big or very small integrating sphere. In
such a case, an alternative method may be used provided that it gives the
same result as that obtained according to this International Standard within
the tolerances allowed by this standard.
Annex A which forms an integral part of this International Standard, is
provided to give a particular method for measuring the spectral
transmittance of mirror lenses.
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INTERNATIONAL STANDARD @ IS0 IS0 8478:1996(E)
Photography - Camera lenses - Measurement of IS0
spectral transmittance
1 Scope
This International Standard specifies a method for measuring the spectal transmittance of camera lenses. It
describes particular conditions for measuring the axial spectral transmittance, over a wavelength range from
350 nm to 700 nm, of camera lenses which are intended to be used mainly for taking pictures of very distant
objects.
If the spectral transmittance values are used exclusively for the calculation of the IS0 colour contribution index (see
IS0 6728) throughout this International Standard, the wavelength range should read 370 nm to 680 nm.
This International Standard is also applicable to mirror lenses (see annex A).
2 Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the edition indicated was valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent edition of the standard indicated below. Members of IEC and IS0 maintain
registers of currently valid International Standards.
Determination of IS0 co/our contribution index (/SO/CC/).
IS0 6728:1983, Photography - Camera lenses -
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 photographic lens: Lens used for recording the image of an object on photosensitive material, such as a
camera or enlarging lens.
NOTE - A projection lens is not a photographic lens.
3.2 camera lens: Lens attached to a still camera used for taking pictures of an object.
3.3 spectral transmittance of a lens: Transmittance denoted by z(a) and defined by the equation
1
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IS0 8478: 1996(E)
where
CD z~ is the transmitted radiant flux of wavelength A;
CD i’A is the corresponding incident radiant flux of wavelength A.
I
4 Apparatus
4.1 General
The apparatus (see figure 1) shall consist of a light source, a condenser lens, a monochromator (or narrow-
bandwidth filters, in limited applications), an aperture stop, a collimator and an integrating sphere together with a
photoelectric detector system.
NOTE - Narrow-band filters are subject to errors due to inter-reflections with other components. The use of narrow-band
filters should be limited to applications where proper corrections can be applied.
I
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IS
AS
a) Using a collimator lens
b) Using an off-axis paraboloid mirror collimator
LS Light source CM Collimator mirror 0 Centre of integrating sphere
C Condenser lens AS Aperture stop d Diameter of beam
M Monochromator IS Integrating sphere
CL Collimator lens DS Detector system
(test lens not shown)
Figure I - Arrangement of the apparatus
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0 IS0
IS0 8478:1996(E)
4.2 Light sources
The light source shall be capable of emitting a spatially and temporally stable radiant flux over the wavelength range
of 350 nm to 700 nm. Spatial variations shall not exceed the acceptance angle of the condenser; temporal variation
shall be less than 1 %.
4.3 Monochromator
The monochromator shall preferably be a double monochromator which shall employ two prisms or two gratings,
or one prism and one grating.
If a grating monochromator is used, it shall employ a filter or filters to cut off the higher-order diffracted radiation.
The wavelength range shall be from 350 nm to 700 nm.
Narrow-band filters may be used in place of the monochromator, provided that there are sufficient filters to cover
the required wavelength interval, and the filters shall have sufficient blocking outside the pass band. Corrections
shall be applied for inter-reflections.
For both the monochromator and the narrow-band filters, the wavelength interval and bandwidth shall be 10 nm or
less and adjustable. A 20 nm interval and bandwidth is satisfactory in the spectral region where the transmittance
variance
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