L i n d a R e y n o l d s

what
makes
type
legible?
This often dismissed as merely
a mater of common sense, but if
common sense is all that is needed,
why is it that some of the basic rules
for good legibility are so frequently
flouted? True, legibility may not
always be the first consideration,
but for words that are intended
to be read it cannot be ignored.

the It has never been difficult to find

legibility
kinds, but examples abound now
that desktop publishing systems
have brought electronic typesetting
within reach of those with little or no

type
knowledge of basic design princi-
of ples. Legibility as an issue is perhaps
more important than ever before.
Some of the most important factors
effecting it are outlined below.
 Choice of Type
type face

vehicle vehicle
serif sans serif

For good legibility, a typeface should have the following characteristics: A relatively large x-height These criteria are satisfied by a number This would suggest that serifs may in- guments, researchers have been unable
in relation to the capital letter height. This will make the lowercase letters easier to discriminate. of typefaces, both seriffed and sans serif. deed help adjacent letters to be grouped to find any significant differences in the
Large, open counters and a relatively generous set width. This will help to prevent letters from Sans serif faces, however, are considered as words, and words to be grouped into legibility of seriffed and sans serif faces.
filling in and running together. Skilled readers recognize whole words by their outline and their by some to be intrinsically less legible lines. It is also argued that seriffed letter Most of us are more familiar with seriffed
internal shape rather than reading letter by letter. If the spaces within a word are lost it will be than serif faces. It is argued that serifs shapes have more individuality and are faces, and it may be that we tend to pre-
difficult or impossible to recognize. Not too much variation between thick and thin strokes. Delicate give horizontal emphasis that helps to therefore more easily distinguished from fer what we’re used to. Provided that the
thin strokes may disappear if the image is photographically reproduced during reproduction. hold letters together as words, and to one another than sans serif letters. Inter- letter, word and line spacing are suitable,
guide the eyes along each line. This may estingly the top halves of lowercase let- a sans serif face is likely to be just as
well be true. The German school of Ge- ters are more important in letter and legible as a seriffed face, and in some
stalt psychologists described a number of word recognition then the bottom halves. situations it may be more so.
principals by which we try to group areas The tops of some sans serif letters are
of the retinal image that are likely to be very much alike, whereas in a seriffed
part of the same figure. One of these is face they are more easily distinguishable.
the principal of direction, also known as Some sans serif faces may also cause
the principal of good continuation, where- problems if it is essential that the.numer-
by separate elements with a common al ‘I’, lowercase ‘l’, and capital ‘I’ should be
direction or trend are seen to form a line. uniquely identifiable. In spite of these ar-
 condensed
and
extended
capitals a A italics a a bold a a type size a a type a aa
Text set in all-capital lettering is less Italics have been shown to be less legi- Bold type is of course invaluable for If the type is too small, letters and word The danger with condensed styles is that
legible than text set in lowercase letters ble than roman letters for continuous text. emphasis, but it is likely to reduce legibil- will be difficult to discriminate. If it is too the letters will either apparently or actual-
with capitals where appropriate. This is This may be because the italic letters are ity when used for continuous text. The large, less words will be perceived at ly fill in and run together. The standard of
because lowercase letters, with their less easily distinguished from one anoth- dense black type tends to create af- each fixation. For a normal reading dis- reproduction needs to be high to ensure
ascenders and descenders, create more er. We are also less used to them. With ter-images, noticeable as bright glowing tance of 12-15 in, the optimum type size good legibility. Extended styles reduce
distinctive word outlines than do capital electronically generated type, so-called areas between the lines. for continuous text is usually somewhere the number of words that can be read at
letters. Any word in capitals has a rectan- ‘italics’ may in fact be a slanted version of between 9pt and 11pt, depending on the each fixation. Normal letter proportions
gular outline. Capitals also take up more the roman letters, rather than a separate- x-height of the typeface and the circum- can be distorted very easily in electronic
space than lowercase letters, so more ly designed font. Some of these ‘obliques’ stances in which the material will be used. typesetting systems, with predictably il-
fixations of the eyes are needed to are likely to have reduced legibility. legible results in many cases.
perceive the same number of words and
this slows reading.

Variations in Letterform
The
Arrangement
of Type on red car
the Page
car c a r red car justified setting line length line spacing
letter spacing word spacing Researchers have been unable to show
any significant difference in the legibility
of justified and unjustified setting for
Line length is a very important factor in
legibility. If the lines are too short, we are
unable to make efficient use of our pe-
For ease of reading, words must be
grouped into lines that the eyes can fol-
low easily. The white space between lines
The space between letters must be suffi- The space between words must of moderate line lengths. There is, however, ripheral vision and the normal pattern of must therefore be greater than the word
cient to separate them clearly. If they course be perceptibly greater than the evidence that less-skilled readers have eye movements is disrupted. If the lines spacing. For continuous text it is almost
touch or appear to touch, legibility will be space between letters within a word. The difficulty with justified setting in very are too long, it is difficult for the eyes to always an advantage to use a linefeed
severely reduced. Where condensed sans Gestalt principle of grouping by ‘proximity’ short lines because of the uneven word make a smooth and accurate ‘back- one or two points greater than the point
serif faces are set tightly spaced, it is is at work here. However, the spacing spacing and frequent hyphenation. Un- sweep’ to the beginning of each new line. size of the type. This is especially true for
common to find letters that have fused to must not be so great that the horizontal justified setting gives constant word We may miss lines or begin reading the line lengths approaching the upper limit
form a different but legitimate word with a emphasis, or ‘good continuation’ of the spacing, thereby avoiding the vertical same line again (‘doubling’). The optimum for good legibility, for typefaces with a
meaning quite different from that intend- line is destroyed. Optimum word spacing white ‘rivers’ so often seen in justified line length for continuous reading is be- strong vertical emphasis (this would in-
ed. If letter spacing is too great, outline will will therefore depend on both letter spac- text. As well as being aesthetically dis- tween about 60 and 65 characters and clude most sans serifs and modern ser-
be diluted and mote difficult to recognize. ing and line spacing. pleasing, rivers destroy the ‘good contin- spaces. Lines of more than 70 charac- iffed faces), and for faces with a relatively
uation’ of the lines, thus making them ters and spaces will reduce legibility and large x-height. If too much space is added,
more difficult to follow. Successful justifi- may be consciously perceived as being however, the lines will appear to drift apart
cation therefore requires a line length of an effort to read. The minimum line and the text will appear lighter in color.
60 or so characters and spaces, a good length for comfort is probably about 40
hyphenation program, and the facility to characters and spaces.
make fine adjustment in word spacing.
Type Black on white versus white on black
and its This is because of the phenomenon of ‘ir-

Background
radiation’, whereby small bright images on

a A
a dark ground will appear to spread. To
counteract this tendency, the typeface
should have open counters and the let-
ters should not be too tightly spaced.
Sans serif faces generally withstand re-

a A
versal better than seriffed faces. There
are no fine serifs or thin strokes to be lost
if the image is thinned-down, and no ser-
ifs to fuse if it becomes thickened.

a A Mechanically
Tinted Backgrounds
When using mechanical tints it is import-
Contrast
For good legibility, the contrast between
ant to look carefully at the dot size in re- type and its background should be at least
lation to the size of the type. The coarser 70%. Thus if the background has a reflec-
the screen, the more likely it is that the tance of 100 units the type should have
dots will distort the letter shapes. Sans a reflectance of not more than 30 units,
serifs tend to survive better than seriffed or vice versa. This is true for coloured im-
faces because of their simpler and more ages too. Complementary colours with
robust letterforms. similar tonal values will cause the type to
appear to vibrate against its background,
a particularly unpleasant effect.