ISO 18946:2011

INTERNATIONAL ISO
STANDARD 18946
First edition
2011-12-15
Imaging materials — Reflection colour
photographic prints — Method for testing
humidity fastness
Matériaux pour l’image — Tirages photographiques en couleurs par
réflexion — Méthode d’essai de la solidité à l’humidité
Reference number
©
ISO 2011
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ii © ISO 2011 – All rights reserved

Contents Page
Foreword . v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
5 Outline of test procedure . 2
6 Sample preparation . 3
6.1 General . 3
6.2 Test target . 4
6.3 Printer driver setting . 5
6.4 Printing conditions. 5
6.5 Sample conditioning . 5
7 Humidity exposure . 6
7.1 Equipment and calibration . 6
7.2 Test environment control . 6
7.3 Method A — Fixed humidity condition . 7
7.4 Method B — Multiple humidity conditions . 7
7.5 Method C — Fixed low-humidity condition . 7
8 Colorimetric measurement . 7
9 Data analysis . 8
10 Test report . 9
10.1 General . 9
10.2 Samples information . 9
10.3 Test conditions . 9
10.4 Results . 9
Annex A (informative) Correspondence to psychophysical evaluation . 11
Bibliography .12
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 18946 was prepared by Technical Committee ISO/TC 42, Photography.
iv © ISO 2011 – All rights reserved

Introduction
This International Standard addresses the methods and procedures for testing the humidity fastness of reflection
colour photographic prints. Low and high humidity exposure are covered. This is of particular relevance to dye-
[10][11][12][13][14][15][16]
based ink-jet prints or dye diffusion process prints .
Some types of colour photographic print suffer from changes in image appearance when exposed to a high
relative humidity environment. The observed changes relate to colour, tone and loss of sharpness caused by
horizontal and vertical diffusion of colorants as a result of exposure to elevated humidity.
The elevated humidity can arise from:
a) exposure to high relative humidity of the environment of the display area or storage space;
b) trapped moisture as a result of stacking prints, or inserting them into albums, in a high relative humidity
environment;
c) trapped moisture as a result of stacking prints, or inserting them into albums, before sufficient dry time has
elapsed.
Therefore, humidity based on meteorological data and users’ behaviour was considered in determining the
appropriate test conditions for the humidity fastness test. The test method stipulated in this International
Standard is validated for case a).
Image deterioration of dye-based prints caused by high humidity is often detectable by the following
characteristics.
— Blur (sharpness loss), change of colour and/or tone is observed.
— The deterioration is observed in higher humidity, commonly over 80 %RH or over 90 %RH.
— The deterioration can occur in a relatively short time, even within one or two weeks.
— Higher density images, or images that contain more secondary or mixed colours, are generally more
affected. The largest change is usually observed at the boundary of different colours, or with images that
have contrasting background colours. The size of the higher density area also affects the deterioration
because the solvent and water of the ink diffuses to the adjacent lower density area when the higher
density area is small.
It is important to take into account these characteristics when determining the appropriate test chart and test
conditions.
It has also been observed that low relative humidities can accelerate the yellowing of certain types of inkjet
papers. Indoor low humidities are common in colder climates as a result of heating air drawn in from the
outdoors with very low dew points, and also in hot, dry climates in combination with air conditioning. In addition
to D yellowing, very low humidities have also been shown to cause physical degradation to image-receiving
min
layers; this phenomenon is outside the scope of this International Standard.
This International Standard makes use of a checkerboard pattern that allows assessment of humidity-induced
[11]
blur by means of a relatively simple colorimetric measurement .
INTERNATIONAL STANDARD ISO 18946:2011(E)
Imaging materials — Reflection colour photographic prints —
Method for testing humidity fastness
1 Scope
This International Standard describes test methods for evaluating reflection colour photographic prints with
regard to changes in image appearance resulting from exposure to both low and high relative humidity.
The observed changes relate to colour, tone and loss of sharpness caused by horizontal and vertical diffusion
of colorants from exposure to elevated humidity levels. Other humidity-related factors, such as mould and
mildew growth, and physical damage, such as curl, cockle, cracking or delamination due to humidity cycling,
are outside the scope of this test method.
Although the method and procedures described in this International Standard can be used to test any colour
hardcopy technology, it is particularly appropriate to systems where the colorants are applied by a mechanism
involving the diffusion of colorant into image-receiving layers, for example inkjet or dye diffusion processes,
and to certain types of inkjet media that are susceptible to D yellowing.
min
2 Normative references
The following referenced documents are indispensable for the application 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 18913, Imaging materials — Permanence — Vocabulary
ISO 18931, Imaging materials — Recommendations for humidity measurement and control
ISO 18941, Imaging materials — Colour reflection prints — Test method for ozone gas fading stability
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts images
ISO 11664-4, Colorimetry — Part 4: CIE 1976 L*a*b* Colour space
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18913 and the following apply.
3.1
operational control point
set point for equilibrium conditions measured at one or more sensor locations in an exposure device
NOTE Adapted from ASTM G113.
3.2
operational fluctuations
positive and negative deviations from the setting of the sensor at the operational control set point during
equilibrium conditions in a laboratory accelerated weathering device
NOTE 1 Operational fluctuations are the result of unavoidable machine variables and do not include measurement
uncertainty. Operational fluctuations apply only at the location of the control sensor and do not imply uniformity of conditions
throughout the test chamber.
NOTE 2 Adapted from ASTM G113.
3.3
operational uniformity
range around the operational control point for measured parameters within the intended exposure area, within
the limits of the intended operational range
NOTE Adapted from ASTM G113.
3.4
uncertainty (of measurement)
parameter, associated with the result of a measurement, that characterizes the dispersion of the values that
could be reasonably attributed to the measurement
NOTE 1 The parameter might be, for example, a standard deviation (or a given multiple of it), or the half-width of an
interval having a stated confidence level.
NOTE 2 Uncertainty of measurement comprises, in general, many components. Some of these components can be
evaluated from statistical distribution of the results of series of measurements and can be characterized by experimental
standard deviations. The other components, which can also be characterized by standard deviations, are evaluated from
assumed probability distributions based on experience or other information.
NOTE 3 It is understood that the result of the measurement is the best estimate of the value of the measurement and
that all components of uncertainty, including those arising from systematic effects, such as components associated with
corrections and reference standards, contribute to the dispersion.
NOTE 4 Adapted from ISO/IEC Guide 98-3:2008, 2.2.3.
4 Requirements
This International Standard specifies a set of recommended test methods with associated requirements for
permitted reporting. Data from these tests shall not be used to make life expectancy claims, such as time-
based print lifetime claims, either comparative or absolute. Conversion of data obtained from these methods
for the purpose of making public statements regarding product life shall be in accordance with the applicable
International Standards for specification of print life.
The test methods in this International Standard might be useful as stand-alone test methods for comparison
of the stability of image materials with resp
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