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The Legibility of Type

Written by Linda Reynolds Design by Shelbie Stuckey

Table of




What Makes Type Legible?

Choice of Type

Serif vs. Sans Serif

A look inside everything you need to know in order to create the most legible type using variations in letterform, arrangement of type on a page, and type backgrounds.

What you choose as a typeface can really either set you up for sucsess or failure depending on how well you are able to identify good type for the right idea.

Know the major differences between these two types of fonts so that when you are in need of just the right typeface for the perfect design, you’ll have it.

09 Type Size Type size is a major factor when putting together an editorial project. There are many different variables to take into consideration while choosing the perfect type size for your project.

10 The Arrangement of Type on A Page Design layouts for text can seem easy until you really delve into what all goes into the arrangement.

11 Line Length and Spacing The way your eye percieves information, especially in the form of text, is extremely important to understand when trying to relay a message with a design.

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Serif vs. Sans Serif Cont.

Variations In Letterforms

Know the major differences between these two types of fonts so that when you are in need of just the right typeface for the perfect design, you’ll have it.

There are endless possibilities that you can do to transform your text into exactly what you need. In order to do that you need to know all of the letterforms that could enhance your design.



Type and it’s Background

Type and It’s Background

The background of type is very important when putting together an editorial project. You have to be sure that they have enough contrast to make it legible.

The background of type is very important when putting together an editorial project. You have to be sure that they have enough contrast to make it legible.

04 | The Legibility of Type

This is 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. It has never been difficult to find examples of illegibility of various kinds, but examples abound now that desktop publishing systems have brought electronic typesetting within reach of those with little or no knowledge of basic design principles. Legibility as an issue is perhaps more important than ever before. Some of the most important factors effecting it are outlined in this book.

What Makes Type Legible?

Choice of Type Type Face For good legibility, a typeface should have the following characteristics:

Large, open counters and a relatively generous set width. This will help to prevent letters from filling in and running together. Skilled readers recognize whole words by their outline and their internal shape rather than reading letter by letter. If the spaces within a word are lost it will be difficult to recognize.

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A relatively large x-height in relation to the capital letter height. By doing this to your typeface, you will make the lowercase letters easier to discriminate.

Not too much variation between thick and thin strokes. Delicate thin strokes may disappear if the image is photographically reproduced during reproduction.

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x-height sans serif



Sans Serif

In spite of these arguments, researchers have been unable to find any significant differences in the legibility of seriffed and sans serif faces. Most of us are more familiar with seriffed faces, and it may be that we tend to prefer what we’re used to. Provided that the letter, word and line spacing are suitable, a sans serif face is likely to be just as legible as a seriffed face, and in some situations it may be more so. T

Serif vs. Sans Serif

other than sans serif letters. Interestingly the top halves of lowercase letters are more important in letter and word recognition then the bottom halves. The tops of some sans serif letters are very much alike, whereas in a seriffed face they are more easily distinguishable. Some sans serif faces may also cause problems if it is essential that the.numeral ‘I’, lowercase ‘l’, and capital ‘I’ should be uniquely identifiable.

07 | The Legibility of Type

These criteria are satisfied by a number of typefaces, both seriffed and sans serif. Sans serif faces, however, are considered by some to be intrinsically less legible than serif faces. It is argued that serifs give horizontal emphasis that helps to hold letters together as words, and to guide the eyes along each line. This may well be true. The German school of Gestalt psychologists described a number of principals by which we try to group areas of the retinal image that are likely to be part of the same figure. One of these is the principal of direction, also known as the principal of good continuation, whereby separate elements with a common direction or trend are seen to form a line. This would suggest that serifs may indeed help adjacent letters to be grouped as words, and words to be grouped into lines. It is also argued that seriffed letter shapes have more individuality and are therefore more easily distinguished from one an-

08 | The Legibility of Type

Variations in Letterform Capitals


Text set in all-capital lettering is less legible than text set in lowercase letters with capitals where appropriate. This is because lowercase letters, with their ascenders and descenders, create more distinctive word outlines than do capital letters. Any word in capitals has a rectangular outline. Capitals also take up more space than lowercase letters, so more fixations of the eyes are needed to perceive the same number of words and this slows reading.

Italics have been shown to be less legible than roman letters for continuous text. This may be because the italic letters are less easily distinguished from one another. We are also less used to them. With electronically generated type, so-called ‘italics’ may in fact be a slanted version of the roman letters, rather than a separately designed font. Some of these ‘obliques’ are likely to have reduced legibility.

Bold Bold type is of course invaluable for emphasis, but it is likely to reduce legibility when used for continuous text. The dense black type tends to create after-images, noticeable as bright glowing areas between the lines.

Condensed and Extended Type The danger with condensed styles is that the letters will either apparently or actually fill in and run together. The standard of reproduction needs to be high to ensure good legibility. Normal letter proportions can be distorted very easily in electronic typesetting systems, with predictably illegible results in many cases.

Type Size If the type is too small, letters and word will be difficult to discriminate. If it is too large, less words will be perceived at each fixation. For a normal reading distance of 12-15 in, the optimum type size for continuous text is usually somewhere between 9pt and 11pt, depending on the x-height of the typeface and the circumstances in which the material will be used.

The Arrangement of Type on the Page

Letter Spacing The space between letters must be sufficient to separate them clearly. If they touch or appear to touch, legibility will be severely reduced. Where condensed sans serif faces are set tightly spaced, it is common to find letters that have fused to form a different but legitimate word with a meaning quite different from that intended. If letter spacing is too great, outline will be diluted and mote difficult to recognize.

The space between words must of course be perceptibly greater than the space between letters within a word. The Gestalt principle of grouping by ‘proximity’ is at work here. However, the spacing must not be so great that the horizontal emphasis, or ‘good continuation’ of the line is destroyed. Optimum word spacing will therefore depend on both letter spacing and line spacing.

Line Spacing For ease of reading, words must be grouped into lines that the eyes can follow easily. The white space between lines must therefore be greater than the word spacing. For continuous text it is almost always an advantage to use a linefeed one or two points greater than the point size of the type. This is especially true for line lengths approaching the upper limit for good legibility (see below), for typefaces with a strong vertical emphasis (this would include most sans serifs and modern seriffed faces), and for faces with a relatively large x-height. If too much space is added, however, the lines will appear to drift apart and the text will appear lighter in color.

Line Length Line length is a very important factor in legibility. If the lines are too short, we are unable to make efficient use of our peripheral vision and the normal pattern of eye movements is

disrupted. If the lines are too long, it is difficult for the eyes to make a smooth and accurate ‘backsweep’ to the beginning of each new line. We may miss lines or begin reading the same line again (‘doubling’). The optimum line length for continuous reading is between about 60 and 65 characters and spaces. Lines of more than 70 characters and spaces will reduce legibility and may be consciously perceived as being an effort to read. The minimum line length for comfort is probably about 40 characters and spaces.

Justified and Unjustified Setting Researchers have been unable to show any significant difference in the legibility of justified and unjustified setting for moderate line lengths. There is, however, evidence that less-skilled readers have difficulty with justified setting in very short lines because of the uneven word spacing and frequent hyphenation. Unjustified setting gives constant word spacing, thereby avoiding the vertical white ‘rivers’ so often seen in justified text. As well as being aesthetically displeasing, rivers destroy the ‘good continuation’ of the lines, thus making them more difficult to follow. Successful justification therefore requires a line length of 60 or so characters and spaces, a good hyphenation program, and the facility to make fine adjustment in word spacing.

11 | The Legibility of Type

“The Gestalt principle of grouping by ‘proximity’ is at work here.”

Word Spacing

Type and It’s Background

12 | The Legibility of Type

Black on White vs. White on Black This is because of the phenomenon of ‘irradiation’, whereby small bright images on a dark ground will appear to spread. To counteract this tendency, the typeface should have open counters and the letters should not be too tightly spaced. Sans serif faces generally withstand reversal better than seriffed faces. There are no fine serifs or thin strokes to be lost if the image is thinned-down, and no serifs to fuse if it becomes thickened.

Mechanically Tinted Backgrounds When using mechanical tints it is important to look carefully at the dot size in relation to the size of the type. The coarser the screen, the more likely it is that the dots will distort the letter shapes. Sans serifs tend to survive better than seriffed faces because of their simpler and more robust letterforms.

Contrast For good legibility, the contrast between type and its background should be at least 70%. Thus if the background has a reflectance of 100 units the type should have a reflectance of not more than 30 units, or vice versa. This is true for coloured images too. Complementary colours with similar tonal values will cause the type to appear to vibrate against its background, a particularly unpleasant effect.



The Legibility of Type  
The Legibility of Type