SIST ISO 18909:2011

INTERNATIONAL ISO
STANDARD 18909
First edition
2006-07-15
Photography — Processed photographic
colour films and paper prints — Methods
for measuring image stability
Photographie — Films et papiers photographiques couleur traités —
Méthodes de mesure de la stabilité de l'image

Reference number
©
ISO 2006
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ii © ISO 2006 – All rights reserved

Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Test methods — General . 1
3.1 Sensitometric exposure . 1
3.2 Processing. 2
3.3 Densitometry . 3
3.4 Definition of density terms . 3
3.5 Density values to be measured . 3
3.6 Method of correction of density measurements for d changes . 3
min
3.7 Computation of image-life parameters. 8
3.8 Effects of dye fading and stain formation on the printing quality of colour negative
images. 9
4 Test methods — Dark stability . 10
4.1 Introduction . 10
4.2 Test conditions . 10
4.3 Number of specimens . 11
4.4 Test equipment and operation for specimens free-hanging in air . 11
4.5 Test equipment and operation for specimens sealed in moisture-proof bags . 12
4.6 Conditioning and packaging of specimens in moisture-proof bags. 12
4.7 Incubation conditions for specimens sealed in moisture-proof bags . 12
4.8 Computation of dark stability . 12
5 Test methods — Light stability . 12
5.1 Introduction . 12
5.2 Number of specimens . 13
5.3 Irradiance measurements and normalization of test results. 13
5.4 Backing of test specimens during irradiation testing. 13
5.5 Specification for standard window glass.14
5.6 High-intensity filtered xenon arc ID65 illuminant (50 klx to 100 klx) for simulated indoor
indirect daylight through window glass. 14
5.7 Glass-filtered fluorescent room illumination — Cool White fluorescent lamps (80 klx or
lower). 16
5.8 Incandescent tungsten room illumination 3,0 klx – CIE illuminant A spectral distribution. 18
5.9 Simulated outdoor sunlight (xenon arc) 100 klx – CIE D65 spectral distribution. 18
5.10 Intermittent tungsten-halogen lamp slide projection 1 000 klx . 21
5.11 Computation of light stability . 21
6 Test report . 21
6.1 Introduction . 21
6.2 Dark stability tests. 23
6.3 Light stability tests . 24
Annex A (informative) Numbering system for related International Standards. 25
Annex B (informative) A method of interpolation for step wedge exposures. 27
Annex C (informative) Method for power equation d correction of reflection print materials. 28
min
Annex D (informative) Illustration of Arrhenius calculation for dark stability . 33
Annex E (informative) The importance of the starting density in the assessment of dye fading and
colour balance changes in light-stability tests. 37
Annex F (informative) Enclosure effects in light-stability tests with prints framed under glass or
plastic sheets. 39
Annex G (informative) Data treatment for the stability of light-exposed colour images. 41
Bibliography . 49

iv © ISO 2006 – All rights reserved

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 18909 was prepared by Technical Committee ISO/TC 42, Photography.
This first edition cancels and replaces ISO 10977:1993, of which it constitutes a technical revision.
Introduction
This International Standard is one of a series of standards dealing with the physical properties and stability of
imaging materials. To facilitate identification of these documents, they are assigned a number within the block
from 18900 – 18999 (see Annex A).
This International Standard is divided into two parts. The first covers the methods and procedures for
predicting the long-term, dark storage stability of colour photographic images; the second covers the methods
and procedures for measuring the colour stability of such images when exposed to light of specified intensities
and spectral distribution, at specified temperatures and relative humidities.
Today, the majority of continuous-tone photographs are made with colour photographic materials. The length
of time that such photographs are to be kept can vary from a few days to many hundreds of years and the
importance of image stability can be correspondingly small or great. Often the ultimate use of a particular
photograph may not be known at the outset. Knowledge of the useful life of colour photographs is important to
many users, especially since stability requirements often vary depending upon the application. For museums,
archives, and others responsible for the care of colour photographic materials, an understanding of the
behaviour of these materials under various storage and display conditions is essential if they are to be
preserved in good condition for long periods of time.
Organic cyan, magenta and yellow dyes that are dispersed in transparent binder layers coated on to
transparent or white opaque supports form the images of most modern colour photographs. Colour
photographic dye images typically fade during storage and display; they will usually also change in colour
balance because the three image dyes seldom fade at the same rate. In addition, a yellowish (or occasionally
other colour) stain may form and physical degradation may occur, such as embrittlement and cracking of the
support and image layers. The rate of fading and staining can vary appreciably and is governed principally by
the intrinsic stability of the colour photographic material and by the conditions under which the photograph is
stored and displayed. The quality of chemical processing is another important factor. Post-processing
treatments, such as application of lacquers, plastic laminates and retouching colours, may also affect the
stability of colour materials.
The two main factors that influence storage behaviour, or dark stability, are the temperature and relative
humidity of the air that has access to the photograph. High temperature, particularly in combination with high
relative humidity, will accelerate the chemical reactions that can lead to degradation of one or more of the
image dyes. Low-temperature, low-humidity storage, on the other hand, can greatly prolong the life of
photographic colour images. Other potential causes of image degradation are atmospheric pollutants (such as
oxidizing and reducing gases), micro-organisms and insects.
Primarily the intensity of the illumination, the duration of exposure to light, the spectral distribution of the
illumination, and the ambient environmental conditions influence the stability of colour photographs when
displayed indoors or outdoors. (However, the normally slower dark fading and staining reactions also proceed
during display periods and will contribute to the total change in image quality). Ultraviolet (UV) radiation is
particularly harmful to some types of colour photographs and can cause rapid fading as well as degradation of
plastic layers such as the pigmented polyethylene layer of resin-coated (RC) paper supports.
In practice, colour photographs are stored and displayed under varying combinations of temperature, relative
humidity and illumination, and for different lengths of time. For this reason, it is not possible to precisely
predict the useful life of a given type of photographic material unless the specific conditions of storage and
display are known in advance. Furthermore, the amount of change that is acceptable differs greatly from
viewer to viewer and is influenced by the type of scene and the tonal and colour qualities of the ima
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