ISO/PAS 18940-1:2025
(Main)Imaging materials — Image permanence specification of reflection photographic prints for indoor applications — Part 1: Test methods
Imaging materials — Image permanence specification of reflection photographic prints for indoor applications — Part 1: Test methods
This document specifies the test methods, test conditions, test target design, and analysis procedures for the evaluation of the image permanence performance of photographic reflection prints. Tests based on ISO 18936, ISO 18937 (all parts), ISO 18941, and ISO 18946 characterize the thermal stability, the light stability, the ozone stability, and the humidity stability of photographic prints, respectively. This document is applicable to any photographic reflection print produced through a digital step in the workflow. It includes prints created by chromogenic silver halide, inkjet, electrophotography, thermal diffusion, and other technologies. With reference to monochrome prints, this document is relevant to photographic prints where the print material contains colorants. This document is not relevant to monochrome silver halide prints, often known as black and white prints. The document specifies the content and procedure for graphical reporting of test results as a first level data collection for basic technical communication of image permanence performance of photographic prints. This document does not include application-specific end-points, environmental conditions during preservation and display of photographic prints, and test doses (durations, intensity).
Matériaux pour l'image — Spécification relative à la permanence de l’image des tirages photographiques par réflexion pour applications intérieures — Partie 1: Méthodes d'essai
General Information
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Standards Content (Sample)
Publicly
Available
Specification
ISO/PAS 18940-1
Second edition
Imaging materials — Image
2025-05
permanence specification of
reflection photographic prints for
indoor applications —
Part 1:
Test methods
Matériaux pour l'image — Spécification relative à la permanence
de l’image des tirages photographiques par réflexion pour
applications intérieures —
Partie 1: Méthodes d'essai
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviations . 2
3.1 Terms and definitions .2
3.2 Abbreviations .2
4 Requirements . 2
5 Test procedures . 2
5.1 Outline .2
5.2 Test target .2
5.3 Light stability test . .4
5.4 Ozone gas stability test .4
5.5 Thermal stability test .4
5.6 Humidity fastness test in high humidity condition .4
6 Measurement . 4
7 Data processing and graph creation . 5
7.1 Data processing.5
7.2 Calculation of colour difference .5
7.3 Graph reporting .6
7.3.1 General .6
7.3.2 Light stability .7
7.3.3 Ozone gas stability .8
7.3.4 Thermal stability .9
7.3.5 Humidity fastness in high humidity conditions .10
8 Reporting .11
8.1 Internal recording .11
8.2 Reporting for external communications . 12
Bibliography . 14
iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO/PAS 18940-1:2023), which has been
technically revised.
The main changes are as follows:
— editorial modifications for clarification based on the comments on the DPAS of the first edition.
A list of all parts in the ISO 18940 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
Test methods for measurement of the image permanence for four important environmental stress factors
for indoor use of photographs are described in the following International Standards:
— ISO 18936 for thermal stability;
— ISO 18937 (all parts) for light stability;
— ISO 18941 for ozone gas stability;
— ISO 18946 for humidity fastness;
— ISO 18949 for low humidity testing.
Humidity testing according to ISO 18946 specifies high humidity test conditions to test for image fastness
(resistance to colorant migration). Humidity testing according to ISO 18949 specifies low humidity test
conditions, which can be observed in hot arid climates and during winter in continental climates. The
importance of low humidity depends on the environmental conditions of the specific usage case. Testing
according to ISO 18949 is optional.
NOTE It is acknowledged that other environmental stress factors can be present during indoor use of photographs
than the four mentioned before. Examples are other atmospheric gases, including SO and NO , the presence of which
x x
depends on local factors such as traffic, industry and heating. Mechanical stresses are also not considered here,
as these are typically considered to be low in the context of indoor consumer use of photographs as compared to
[3]
commercial applications (see ISO/TS 21139-1 ).
Each document includes variants of the test methods, test conditions and data analysis procedures to cover
different purposes. For the purpose of an overall specification for indoor image permanence performance, it
is necessary to specify which method, which condition and which data analysis procedure to select.
This document specifies the test methods, the test conditions and details of the data analysis. This document
also specifies how to communicate the results obtained by these test methods.
This document specifies which test method, test conditions and data analysis procedure are selected from
those listed in ISO 18936, ISO 18937 (all parts), ISO 18941, and ISO 18946.
In addition, this document also specifies the first level reporting of the results from the aforementioned
test methods in terms of data plots, which is the most generic reporting method. Graphical reporting
addresses the needs of communication on various levels, including technical product information on
datasheets, internet home pages, leaflets and posters distributed at trade shows. Graphic reporting is a key
for this document, as it provides the foundation for defining end-point criteria and specifications of image
permanence in other parts of this document.
Additional parts of the ISO 18940 series are being envisaged as future work to define standardized evaluation
point criteria on one hand and typical environmental conditions on the other, so that 'typical' expectations
for colour changes in the use profile 'consumer home' are taken into consideration. These additional parts
acknowledge that the actual expectations, use conditions (display and/or storage, including a certain level of
protection) as well as the actual environmental conditions in a specific instance of the use profile may vary.
More information on the image permanence issues of the consumer home environment can be found in
[2]
ISO/TR 18942 .
v
Publicly Available Specification ISO/PAS 18940-1:2025(en)
Imaging materials — Image permanence specification of
reflection photographic prints for indoor applications —
Part 1:
Test methods
1 Scope
This document specifies the test methods, test conditions, test target design, and analysis procedures for
the evaluation of the image permanence performance of photographic reflection prints. Tests based on
ISO 18936, ISO 18937 (all parts), ISO 18941, and ISO 18946 characterize the thermal stability, the light
stability, the ozone stability, and the humidity stability of photographic prints, respectively.
This document is applicable to any photographic reflection print produced through a digital step in the
workflow. It includes prints created by chromogenic silver halide, inkjet, electrophotography, thermal
diffusion, and other technologies. With reference to monochrome prints, this document is relevant
to photographic prints where the print material contains colorants. This document is not relevant to
monochrome silver halide prints, often known as black and white prints.
The document specifies the content and procedure for graphical reportin
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