Legibility
Legibility has been given many names - among them discernability, readability, and visibility - some
of which have the same meaning and others which only partially define the term.
Legibility literally means "able to be read". This ability to be read combines visibility (the quality of being seen)
with comprehension (understanding). Perception has a lot to do with legibility. It is by this complex process that we
select, interpret and organize sensory stimuli into coherent pictures; then these shade into perception as we relate
what we see and feel with past learning.
Information perception is basically a process of reducing uncertainty by identifying regularities; information is defined
in terms not of content, but of regularity as opposed to randomness. The more signals available to be picked up, the
easier it is to identify the information. At the same time, if an image is incomplete it is usually possible to determine
the meaning by combining the information contained in the image.
The typefaces now generally in use are all capable of being read without difficulty; types which are not legible do
not remain in general use for long. But the legibility of any series depends to some extent not only on the letter-forms
but on the way they are arranged and printed.
Studies in legibility
A number of scientific studies have been carried out during this century by researchers to determine the optimal level
of legibility for a typeface. They have all come up with results, many of which are later superseded by using different
research techniques. Among these research projects, and the ones that I will be focusing upon are Legibility of Print
(M.A. Tinker, 1963), Readability of Print (H. Spencer, 1968), and Typographic i (I.T.C.A., circa 1979). I will also be
selecting information from a number of other sources which mention differences of opinion concerning the study of legibility.
A list of books you may want to refer to appears at the end of this article.
The first studies in legibility were carried out by Erdman and Dodge (1898) who observed the way both children and adults
read. They discovered that reading was made up of a variety of eye movements - left to right in short jerky motions,
pausing for a split second and moving backwards (regressing) over misunderstood words or phrases. By counting the number
of regressions in a passage, they were able to determine the readability of the piece.
In order to fully comprehend the nature of the readability of a printed page, the researchers carefully evaluated each
element of the page - type, styles, size, width, leading margins, effect of coloured inks, light sources and the weight
and type of paper used. Many of these elements can be controlled by someone involved in the typographical and print production
cycle; the rest can only be controlled by the reader.
Legibility is affected by and dependent on the visual sharpness of the reader: his age, reading ability, and the mood
of the moment; his preference for colour, texture and proportion; the degree of interest in the subject; the angle that
the page is held at, and the position of the reader, whether he is sitting or standing, with good or bad lighting or
in a disruptive or peaceful environment.
There are different kinds of reading: a novel, a cookery book, a dictionary or a telephone directory are all read, but
in different ways, which must affect the typographers choice of setting. Business men, for example, have to read hundreds
of reports, and the way these are presented may make a great deal of difference to their readers. Some reports have to
be read carefully and absorbed, and these reports should follow the rules of book setting. Other reports can be read
quickly, scanned and so they can be set with shorter lines and greater interlinear spacing.
Another factor, which is related to the age and reading skills of the reader is experience. The typefaces that the reader
has grown up with will affect the legibility for a particular generation of readers. Two interesting speculations have
been made as to when this preference for a particular type style are developed in a reader. The first suggests that during
the first four years of schooling typeface styles are impressed upon the child (Burt, 1955); the second, suggests that
the typefaces that a child has become accustomed to reading in his material at age ten (when eye movements have stabilised)
would be most legible throughout his reading life.
When preparing a piece, a designer must always ask: What, why, for whom, when and where? If the piece is to be read
by people from a particular linguistic background, their needs must be adequately met. Although this article deals specifically
with the legibility of type, it is important to realise that not all readers are able to communicate with textual language
and so the designer must be aware of, and learn to use, a variety of other communication techniques, including icons,
illustrations of all kinds, diagrams and charts.
Legibility Research Findings
Serifs
It is stated by many researchers that serif faces are intrinsically more legible than sans serif faces. The reason for
this is that sans serif letters are more similar to one another than serif letters and so the certainty of decipherment
of the shapes of letters is reduced. The result of this is that body text set entirely in a sans serif face makes for
dull and unattractive reading - the page is all of one colour, with nowhere for the eye to rest. This monotony can be
avoided by using various devices in the setting of the text - using subheadings, breaking paragraphs, adding illustrations
or photographs, etc - to break up the text.
However, as mentioned earlier, researchers have tended to ignore the experience of the reader and it is likely that
a person brought up almost entirely on sans serif typefaces will have little difficulty deciphering the shapes of letters
in body copy.
Word Spacing
Extreme spacing between words opens up rivers of space down the page, across the reader's eye and breaks up the text
so that it takes on the appearance of irregular patches of words instead of a series of lines. The use of 3 to em and
4 to em word spaces are recommended to maintain the continuous colour of type masses.
An interesting point concerns the use of spacing after a full stop. Typists have always used the rule that there should
be two space-bar spaces after end-of-sentence punctuation; it is common practice these days to place a single space after
a full stop or other similar punctuation. However, either of these methods can create rivers of white between sentences.
The best way to reduce this problem is to place no extra spacing after end-of-sentence punctuation and instead to rely
on word spacing to separate the sentences. The full-stop, for example, will give the impression of greater space as will
the first letter capital, which along with the context tells the reader's eye that a new sentence has begun.
Interlinear spacing
Several factors influence the choice of leading. Before "leads" were used in compositions, text was set solid with no
space betwen lines. This was acceptable because the ascenders and descenders of classical letters were long enough to
provide plenty of space between the lines. The rise of modern letters has seen these extenders reduce in size and so
leading has been introduced to ensure that the type is readable.
Leading has an important effect on the legibility of type. Legibility depends not only on being able to see the strokes
which make up letters, but being able to see at a glance the positions of these strokes in relation to one another. If
there is too much or too little space within or between the letters, the positions and shapes of the strokes become confused,
and the letters less easy to identify quickly. If the lines of letters are too close, overcrowding the area of attention,
they distract the reader. Excessive leading, on the other hand, seems to diminish legibility (Burt).
Text type arrangement
A number of non-optimal factors combined though not strictly cumulative may drastically reduce reading efficiency. (Spencer,
1968)
The design of a printed piece may contain matter other than the type, including illustrations, lines, fleurons, photographs
or charts and maps. Added to these page elements are the size of the page itself. Here again, the experience of the reader
is important. Readers who are brought up to read from American page sizes will find adult reading from these pages easier;
other readers may find European page sizes easier.
Further the arrangement of text in columns will affect the legibility of a piece of text. It was discovered that margins
should be 50% of the total area of the page and that there were four possible inter-columnar spacing arrangements. These
arrangements were: 1/2 pica space, 1 pica space, 2 pica space, a rule with 1/2 pica space each side, a rule with 1/4
pica space each side and a rule with no extra space. (Tinker, 1963)
Indention of paragraphs was found to be important in improving the speed of reading. However, the curious practice of
indenting every other line in a paragraph was found to severly retard the speed of reading.
Background
Designers and typographers have long since realised that reading white type on a black background is more difficult
than black on white, although in small quantities it can be an attractive way to draw the eye to a display heading. However,
for some reason there are some designers who persist in printing long tracts of white text on black backgrounds, or worse
still green on red or red on black.
In 1878, yellow tinted papers were suggested as being the easiest tint for reading black. However, a common complaint
concerning this edict was that no one knew which tint of yellow, nor which black ink should be used. Twenty years later,
it was suggested that hard surfaced, unglazed, opaque and handmade papers were more suitable. In 1925, the paper most
preferred by researchers had no gloss and was as white as possible so that it made a clean impression and had no show-through.
Since then the preference has been for highly finished papers, either dull or glossy which have been found to be equal
in properties affecting legibility.
Capital letters
The consensus of opinion throughout most reports on legibility seems to be that to use all capitals in copy is less
likely to be read as easily as to use a combination of lower case and capitals; 96% of readers prefer lower case (Tinker,
1963). Apart from anything else, the length of the alphabet in capitals in much greater than that for lower case letters.
Of course, this means that the setting of text (particularly headings) in capitals creates a longer line or forces the
typesetter to split a headline into two lines. The use of all capitals is usually designed to draw attention to the most
important part of a story - the heading is designed to catch the readers eye and lead him into the body copy.
Recognition of words is almost entirely visual and each word is seen as a shape before its meaning is perceived. Use
of lower case letters improves the quality of the shape of letters.
Conclusion
These results by no means reflect the fullness of research undertaken into legibility. There are a number of other areas
for which I have not given any details. If you are sufficiently interested in the subject, you can refer to any of the
books listed at the end of this article.
The findings of most laboratory tests of legibility prove, if they prove anything, what suited those people, of that
age and gender, at that time of day (tired? well-fed? hungry? in good or bad temper?), in that month, in those conditions.
(McLean)
Typographers have always learnt much of this type of information through long experience; but the knowledge has rarely
been made available to anyone outside the industry. However, as with most common sense data, it takes scientific experimentation
for the expreience to be accepted as true and for the information to be compiled into a publicly accessible format.
Changing experimental techniques and improved understanding of the human psyche will, no doubt, alter much of this information,
and further studies will be conducted to discover the optimium legibility factors for each new generation of readers.
Text Legibility
The ingredients of a legible typeface. Edwin Shaar of Harris Corporation.
- Alignment of type: A variation of one or two thousands of an inch is noticeable.
- Optically corrected face: Optical correction compensates for failure of the eye to differentiate realities from illusions.
An example is the need to slightly increase the size of round letters over that of square letters.
- Uniform letter proportions in font: This involves thickness of stroke, length of serif, and evenness of colour when
seen in mass.
- Contrast within font: Italic and boldface contrast with the regular weight of roman.
- Clear symbol identification: All symbols should be clearly distinguished so that the numeral 1 cannot be mistaken
for 7 or cap I or lowercase l, or a G confused with an O or a Q. The upper half of letters should be particularly recognisable.
- Fitting: Good linkage of one letter to another when composed together.
- Large x-height: The x-height should be as large as possible without unduly sacrificing the size of the ascenders
and descenders.
- Printability: No ink traps; open counters in b, d, o, p, q, a, e, and g.
- Familiarity of form: The typeface should have no strange mannerisms, should offer no distractions, and should appear
easy and warm to the reader.
Written by Geoffrey Fletcher (First appeared
in Australian Macworld, 1990)
Previous Contents Next
|
