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 respect to one specific failure mode. Data from the test methods of this
International Standard may be used in stand-alone reporting of the absolute or comparative stability of image
materials with respect to the specific failure mode dealt with in this International Standard, when reported in
compliance with the reporting requirements of this International Standard. Caution shall be exercised when
comparing test results for different materials. Comparisons shall be limited to test cases that use equipment
with matching specifications and matching test conditions.
5 Outline of test procedure
[11]
The checkerboard pattern shown in Figure 1 shall be printed at (23 ± 2) °C and in an environment of
(50 ± 10) %RH.
The test samples shall be conditioned, positioned with unrestricted airflow, for (24 ± 2) h at (23 ± 2) °C and
(50 ± 5) %RH.
The printed samples shall be exposed to high humidity or low humidity as specified in Clause 7.
The colour patches shall be measured using CIELAB colorimetry before and after the humidity exposures.
∗
ΔE for the patches of the checkerboard pattern shall be calculated.
ab
This International Standard stipulates three test methods: A, B, and C.
Method A demonstrates the degree of the deterioration (∆E of the printed image) quantitatively in a fixed
humidity condition, i.e. 25 °C and 85 %RH, for a given period of time. Four weeks is the recommended duration.
One, two or eight week durations can be used. Method A is most useful for research and development of
2 © ISO 2011 – All rights reserved

printing systems or printing materials where the humidity fastness of many samples can be screened and
closely compared.
Method B demonstrates the limitations of printing systems and materials by analysing data from tests at various
levels of humidity, i.e. 25 °C for two weeks at three or more humidity levels chosen from 60, 65, 70, 75, 80,
85, 90 and 95 %RH, and showing where each sample starts to deteriorate. Method B is especially useful for
communicating with end users who will be able to recognize the high humidity limitations for each product
tested.
Method C demonstrates the propensity of the image-receiving layer or underlying substrate to yellow upon
[18]
exposure to low relative humidities, i.e. 25 °C at 20 %RH for up to six months .
The test procedures are summarized in Table 1.
Table 1 — Summary of test procedures
Steps Procedures and test conditions
Test target Checkerboard pattern shown in Figure 1
Sample preparation
Temperature (23 ± 2) °C and (50 ± 10) %RH
and RH
Temperature (23 ± 2) °C and (50 ± 5) %RH
and RH
Sample conditioning
Duration (24 ± 2) h, unrestricted airflow
Method CIE colorimetry conforming to measurement condition M0 of
ISO 13655
Measurement
Parameter ∗
ΔE of 84 patches in Figure 1 before and after the humidity
ab
exposure
Method A 25 °C and 85 %RH
Recommended duration of 4 weeks
One, two or eight week durations can be used
Humidity exposure
Method B 25 °C for two weeks at three or more humidity levels chosen from
60, 65, 70, 75, 80, 85, 90 and 95 %RH
Method C 25 °C at 20 %RH for up to six months
Method CIE colorimetry conforming to measurement condition M0 of
ISO 13655
Measurement
Parameter ∗
ΔE of 84 patches in Figure 1 before and after the humidity
ab
exposure
Methods A and C Measured deterioration at a fixed humidity
Report
Method B Highest limit humidity without significant deterioration
6 Sample preparation
6.1 General
The checkerboard pattern shown in Figure 1 shall be printed at (23 ± 2) °C and (50 ± 10) %RH.
The test samples shall be conditioned for (24 ± 2) h at (23 ± 2) °C and (50 ± 5) %RH before humidity exposure,
positioned with unrestricted airflow.
1)
The sample holding environment shall be ozone-free [≤2 nl/l average ozone concentration over any 24 h
period] for ozone-sensitive samples, as determined in accordance with ISO 18941. A material that is not
sensitive to ozone shall have demonstrated no measurable D or printed patch colour change at ambient
min
1) 1 nl/l = 1ppb (1 ×10−9). Although the notation “ppb” (parts per billion) is widely used in the measurement and reporting
of trace amounts of pollutants in the atmosphere, it is not used in International Standards because it is language-dependent.
ozone exposure levels and measurement condition temperature and humidity, over time periods consistent
with measurement and test-staging time periods.
At least two replicate prints are required for each test case. Replicates shall be located for testing in different
regions of the test chamber volume.
It is recommended that reference samples be included in every exposure test to track consistency of the test
[9]
procedures as well as unintended changes of test conditions .
6.2 Test target
The checkerboard test pattern (see Figure 1) shall be used as the test target. This test file is contained in the
Humidity Print Stability Digital Test File collection and is available at http://www.i3a.org/resources/#iso. The
standard Humidity Print Stability Digital Test File shall be downloaded and maintained in the tiff file format. No
lossy image or file compression shall be applied to the target file. The digital file resolution shall be maintained
as 600 dpi. The Humidity Print Stability Digital Test File is encoded in sRGB, defined as per IEC 61966-2-1, and
uses the tiff format with the sRGB ICC profile embedded. After downloading, the Humidity Print Stability Digital
Test File shall be retained in that format and encoding with the ICC profile retained.
NOTE Other file formats that retain the state of exactly unchanged pixel encoding values, no lossy compression,
embedded sRGB ICC profile, and 600 dpi, can be treated as equivalent to the tiff format for internal use in a test environment.
This test pattern contains all of the cyclic combinations of Y, M, C, R, G, B, white and black as a checkerboard
pattern. Rows 1, 7, 13 and 14 consist of solid-fill colour patches, which are used to evaluate changes in colour
quality. Rows 2 to 6 and 8 to 12 consist of colour patches with a fine checkerboard pattern of interleaved colour
squares which manifest colour changes that correlate well with loss of line quality caused by lateral migration
of colorants.
This test target was created to measure both colour and tone change and blur of the checkerboard pattern.
The change in the CIELAB c
...