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IS0
I N T ER N AT1 O N A L ORGAN I Z AT 1 ON FOR S TA N DARD IZAT I O N
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I SO R EC O M M EN DATI O N
R 435
IS0 CONVENTIONAL TYPOGRAPHICAL CHARACTER
FOR LEGIBILITY TESTS (IS0 CHARACTER)
1st EDITION
April 1965
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 435, IS0 Conventional Typographical Character .for Legibility
Tests (IS0 Character), was drawn up by Technical Committee ISO/TC 46, Documentation,
the Secretariat of which is held by the Nederlands Instituut voor Documentatie en Registratuur
(N.I.D.E.R.) on behalf of the Stichting Nederlands Normalisatie-instituut ("1).
Work on this question by the Technical Committee began in 1952 and led, in 1958, to the
adoption of a Draft IS0 Recommendation.
In November 1961, this Draft IS0 Recommendation (NO 482) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial
nature, by the following Member Bodies :
Poland
Australia Greece
Austria Hungary Portugal
Belgium India Romania
Brazil Israel Spain
Canada Italy Sweden
Switzerland
Czechoslovakia Japan
Denmark Netherlands Turkey
France New Zealand United Kingdom
Germany Norway U.S.A.
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in April 1965, to accept it as an IS0 RECOMMENDATION.
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ISO/R 435 - 1965 (E)
FOREWORD
No documentary reproduction process can avoid giving a more or less impaired image of the
characters and illustrations of the original document.
The user is sensitive to this impairment of the legibility of the image, the effects of which range
from the impossibility of identifying certain details to the fatigue caused by prolonged reading.
Introduced in this way, the concept of legibility may seem subjective, and therefore more difficult
to define than are the characteristics usually taken into consideration in this connection by
photographers and opticians: for example, resolving power of optical devices, blurring of net-
works of parallel lines, graininess of the image. But users are less directly conscious of such
characteristics, and it seemed desirable to endeavour to make legibility accessible to experiment
and even, up to a point, measurable, by specifying with great accuracy a recommended conven-
tional typographical character.
This character, which may vary in orientation and size, is mainly used for making legibility
mires or legibility test objects comparable to the typographic mires or test objects used in print-
ing practice. Microcopies are made from these test objects and are known as micromires or
nzicro-test objects.
The main practical applications of the IS0 character are based especially on the following expe-
rimental properties :
(a) If from a group of test characters of a certain height a particular document reproduction
process produces an idenfiJiable image, it can be assumed that the same process will
produce, from a printed text of comparable typeface size, a satisfactory image and, in
particular, one sharp enough to be read for a certain time without undue fatigue for
the reader.
(b) In general, the identification of one and the same group of IS0 characters by different
observers gives substantially identical results.
The use of test objects and micro-test objects gives manufacturers of reading apparatus,
operators and users on the one hand useful means of investigation, and on the other
hand the elements of a common language for judging the quality of their apparatus
or work.
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IÇO/R 435 - 1965 (E)
IS0 Recommendation R 435 April 1965
IS0 CONVENTIONAL TYPOGRAPHICAL CHARACTER
FOR LEGIBILITY TESTS (IS0 CHARACTER)
1. NATURE OF IS0 CHARACTER
The IS0 character is a conventional typographical character, similar to printing typeface and
accurately defined as to shape and size.
2. DESCRIPTION
2.1 Shape
The IS0 character consists of a regular octagon with two interior parallel stripes, as shown
in Figure 1 below.
The dark stripes and the clear spaces between them are of the same width and can be oriented
in four different ways (vertically, horizontally, 45" to the right, 45" to the left).
.
C'CI c'c'c c c
7777777
FIG. 1. - Enlarged drawing of the IS0 conventional typographical character for legibility tests
2.2 Sizes
2.2.1 Sizes of characters for mires (test objecfs)
The standard sizes (see clause 3.1) of the IS0 characters to be used for mires (test
objects) (see clause 4.3) are, in hundredths of a millimetre,
80 100 125 160
50 63
This range can be extended at each end in terms of the R 10 series of preferred numbers
(see IS0 Recommendation R 3, Preferred Numbers. Series of Preferred Numbers) *.
2.2.2 Sizes of characters for micromires (micro-test objects)
...