ISO 8478:2017

INTERNATIONAL ISO
STANDARD 8478
Second edition
2017-11
Optics and photonics — Camera
lenses — Measurement of ISO spectral
transmittance
Optique et photonique — Objectifs photographiques — Mesurage du
facteur spectral de transmission ISO
Reference number
ISO 8478:2017(E)
©
ISO 2017

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ISO 8478:2017(E)

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ISO 8478:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 2
5 Conditions. 3
6 Procedure. 4
7 Presentation of the results . 5
Annex A (normative) Method for measuring spectral transmittance of mirror lenses .6
Bibliography . 8
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ISO 8478:2017(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.
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee
SC 1, Fundamental standards.
This second edition cancels and replaces the first edition (ISO 8478:1996), of which it constitutes a
minor revision.
The main changes compared to the previous edition are as follows:
— the document has been updated to current drafting rules;
— A.2 b) has been adjusted.
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ISO 8478:2017(E)

Introduction
This document 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 document 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 document 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 minimum f-number.
In the case of lenses with very long or short focal lengths, the measuring method specified in this
document 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 document within the tolerances allowed by this document.
Annex A, which forms an integral part of this document, is provided to give a particular method for
measuring the spectral transmittance of mirror lenses.
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INTERNATIONAL STANDARD ISO 8478:2017(E)
Optics and photonics — Camera lenses — Measurement of
ISO spectral transmittance
1 Scope
This document specifies a method for measuring the spectral 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 ISO colour contribution
index (see ISO 6728) throughout this document, the wavelength range reads 370 nm to 680 nm.
This document is also applicable to mirror lenses (see Annex A).
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:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
photographic lens
lens used for recording the image of an object on photosensitive material, such as a camera or
enlarging lens
Note 1 to entry: 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 τλ() and defined by the formula
Φ
τλ,
τλ()=
Φ
i,λ
where

is the transmitted radiant flux of wavelength, λ;
Φ
τλ,

Φ
is the corresponding incident radiant flux of wavelength, λ.
i ,λ
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ISO 8478:2017(E)

4 Apparatus
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.
...