ISO 17221:2014

INTERNATIONAL ISO
STANDARD 17221
First edition
2014-05-01
Plastics — Determination of image
clarity (degree of sharpness of
reflected or transmitted image)
Plastiques — Détermination de la clarté de l’image (degré de netteté
de l’image réfléchie ou transmise)
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Instrument . 1
6 Test specimen . 4
7 Procedure. 4
7.1 Zero adjustment . 4
7.2 Sensitivity adjustment . 5
7.3 Measurement on the test specimen . 5
8 Calculation . 5
9 Test report . 6
Annex A (informative) Example of determination . 7
Annex B (informative) Precision .10
Bibliography
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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
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The committee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 5, Physical chemical
properties.
iv © ISO 2014 – All rights reserved

Introduction
Visual assessment of the image clarity of plastics is carried out by evaluating the sharpness of an
image reflected from a surface, using a specified incident angle, for reflection. For transmission, image
sharpness is evaluated by viewing a suitable target through the plastic. The degree of image clarity
is influenced by the clearness, surface irregularities and haziness of surfaces. Gloss meters and haze
meters do not correctly access this phenomenon. Image clarity is not the same as and should not be
confused with gloss or haze. Therefore, standardized methods for determining the optical parameter of
image clarity are needed.
INTERNATIONAL STANDARD ISO 17221:2014(E)
Plastics — Determination of image clarity (degree of
sharpness of reflected or transmitted image)
1 Scope
This International Standard specifies an instrumental method for determining the image clarity on
plastics specimens by measuring reflection from the specimen surface or transmission through the
specimen.
The method can be applied only to a flat surface.
NOTE For same materials, different values of image clarity can be obtained depending on specimen
preparation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 472, Plastics — Vocabulary
ISO 2813, Paints and varnishes — Determination of specular gloss of non-metallic paint films at 20°, 60°
and 85°
ISO 11664-1, Colorimetry — Part 1: CIE standard colorimetric observers
ISO 11664-2, Colorimetry — Part 2: CIE standard illuminants
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following apply.
3.1
image clarity
degree of sharpness of an image reflected by a specimen or transmitted through a specimen
Note 1 to entry: Image clarity is expressed in percentage (%).
4 Principle
For the measurement of image clarity, a lamp illuminates the narrow source aperture-slit. The collimating
lens projects a parallel beam upon the specimen. The image is either reflected from or transmitted
through the specimen, as appropriate. The image is received by the de-collimating lens and focused
upon the optical mask. The light passing through the optical mask is received by the light receptor. This
resultant signal is processed yielding image clarity values.
5 Instrument
5.1 Light source and spectral response. The light source and the photometer shall be used in
conjunction with a filter to provide an output corresponding to the photopic standard luminous efficiency
V(λ), which is identical to the colour-matching function y(λ) specified in ISO 11664-1, under CIE standard
illuminant A as specified in ISO 11664-2. The output of the photodetector shall be proportional to the
incident flux, to within 1 % of the incident flux, over the range used. The spectral and photometric
characteristics of the light source and photometer shall be kept constant during measurements.
5.2 Slit, 0,03 mm ± 0,01 mm in width and not less than 20 mm in length.
5.3 Optical mask, consisting of opaque and transparent lines having the same width and spacing. Six
different groups of lines having different widths are utilized. An optical mask is illustrated in Figure 1.
Table 1 gives the dimension for the lines of the optical mask.
Key
a opaque area Group 1 transparent and opaque lines each 2,0 mm in width
b transparent area Group 2 transparent and opaque lines each 1,0 mm in width
c width of opaque area Group 3 transparent and opaque lines each 0,5 mm in width
d width of transparent area Group 4 transparent and opaque lines each 0,25 mm in width
Group 5 transparent and opaque lines each 0,125 mm in width
Group 6 opaque line 1,0 mm in width
Figure 1 — Optical mask of image clarity
Table 1 — Optical mask (dimensions)
Optical mask line
Tolerance Group width
Group No. width Quantity
mm mm
mm
1 2,000 4 ±0,200 16
2 1,000 6 ±0,100 12
3 0,500 9 ±0,050 9
4 0,250 16 ±0,025 8
5 0,125 21 ±0,013 5,25
1,000
6 1 ±0,100 1
(only opaque)
NOTE Other dimensions of the optical mask may be used depending on the surface structure of the specimen if agreed
upon between the interested parties.
2 © ISO 2014 – All rights reserved

5.4 Geometry (for reflection measurement). The normal geometry is 45°:45°. The 60°:60° may be
used if agreed upon between the interested parties.
NOTE The 60°:60° geometry may be used depending on the surface structure of the specimen for conforming
the visual assessments.
5.5 Black glass standard, giving a constant light intensity when any of the five line widths of optical
mask is used for passing light. The bottom level of the waves is defined as the standard zero level.
The black glass standard surface used should conform to specifications such as given in ISO 2813.
5.6 Structure. A diagrammatic representation of the apparatus used for evaluation of image clarity
in transmission is shown in Figure 2. Figure 3 shows a diagrammatic representation for reflection
measurement of image clarity.
Key
1 light source 5 de-collimating lens with a focal length 130 mm
2 source aperture-slit 6 optical mask
3 collimating lens with a focal length 130 mm 7 image of source aperture-slit on the optical mask
4 specimen 8 light receptor
Figure 2 — Typical diagrammatic representation for transmission measurement of image
clarity
...