ISO/PAS 18940-1:2023

PUBLICLY ISO/PAS
AVAILABLE 18940-1
SPECIFICATION
First edition
2023-09
Imaging materials — Image
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 2023
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Published in Switzerland
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 Test target . 2
5.2 Light stability test . . 3
5.3 Ozone gas stability test . 4
5.4 Thermal stability test . 4
5.5 Humidity fastness test in high humidity condition . 4
6 Measurement .4
7 Data processing and graph creation .4
7.1 Data processing. 4
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 . 9
8 Reporting .10
8.1 Internal recording . 10
8.2 Reporting for external communications . 11
Bibliography .12
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 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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 42, Photography.
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 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.
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
2 x
presence of which 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 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.
The ISO 18940 series specifies the test methods, the test conditions and details of the data analysis. The
ISO 18940 series 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 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 standard.
Additional parts of the ISO 18940 series are being envisaged as future work to define standardized
evaluation point criteria on the 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
ISO/TR 18942.
v
PUBLICLY AVAILABLE SPECIFICATION ISO/PAS 18940-1:2023(E)
Imaging materials — Image permanence specification of
reflection photographic prints for indoor applications —
Part 1:
Test methods
1 Scope
This document specifies the test methods, the test conditions, the test target design, and the analysis
procedures for the evaluation of the image permanence performance of digital 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.
This document is applicable to any digital photographic reflection print, which includes prints created
by chromogenic silver halide, inkjet, electrophotography, thermal diffusion, and others. Black and white
prints composed of metallic silver are not within the scope, but monochrome prints where the printing
process contains dyes are within the scope.
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.
Application-specific end-points, environmental conditions and test doses (durations, intensity) are not
included in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references the latest edition of the referenced document (including any amendments) applies.
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts
images
ISO 18924, Imaging materials — Test method for Arrhenius-type predictions
ISO 18936:2020, Imaging materials — Processed colour photographs — Methods for measuring thermal
stability
ISO 18937-2:2023, Imaging materials — Methods for measuring indoor light stability of photographic
prints — Part 2: Xenon arc lamp exposure
ISO 18941, Imaging materials — Colour reflection prints — Test method for ozone gas fading stability
ISO 18944, Imaging materials — Reflection colour photographic prints — Test print construction and
measurement
ISO 18946, Imaging materials — Reflection colour photographic prints — Method for testing humidity
fastness
ISO/CIE 11664-1, Colorimetry — Part 1: CIE standard colorimetric observers
ISO/CIE 11664-4, Colorimetry — Part 4: CIE 1976 L*a*b* colour space
3 Terms, definitions and abbreviations
3.1 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.2 Abbreviations
CIE: Commission internationale de l'éclairage (International Commission on Illumination)
4 Requirements
To be in accordance with this document, the user shall provide graphical reporting of image permanence
testing associated with all four environmental stress factors required in this document, one at a time,
including light, heat, ozone, and humidity. If the result of one or several stress factors is not available, it
shall be reported that there is no result of that stress factor.
5 Test procedures
5.1 Test target
For light, ozone and thermal stability tests, the test target shall consist of the 24 patches with sRGB
values defined in Table 1. The requirements for preparation, printing, handling and measurement of the
test target defined in ISO 18944 apply. When preparing the test target prints, the sRGB values of Table 1
are used to construct the test patches instead of the sRGB values defined in ISO 18944:2018, 5.3.2 and
Annex A. Test targets for high humidity testing are defined in ISO 18946.
An example of test target design is shown in Figure 1.
NOTE 1 This test target was created based on ISO 18944:2018, Table A.1. However, in order to reduce the test
load, the number of patches was reduced from 357 to 24, and 3 brown patches were added.
Table 1 — Colour patch of the test target - RGB values of input signal in 8 bit
Number 1 2 3 4 5 6 7 8 9 10 11 12
Name of col- Dark Me- Light Dark Medi- Light Dark Me- Light Dark Dark Dark
our patch Yellow dium Yellow Ma- um Ma- Cyan dium Cyan Blue Green Red
Yellow genta Ma- genta Cyan
genta
Digital R 255 255 255 255 255 255 32 64 128 64 64 255
value in
G 255 255 255 32 64 128 255 255 255 64 255 64
8 bit
B 32 64 128 255 255 255 255 255 255 255 64 64

Number 13 14 15 16 17 18 19 20 21 22 23 24
Name of col- Black Dark Me- Me- Light White Dark Me- Light Light Light Light
our patch Grey dium dium Grey brown dium brown Blue Green Red
Grey-1 Grey-2 brown
Digital R 0 32 64 128 192 255 131 204 230 12
...