9.2 Understanding font characteristics

There are many design principles that divide fonts into individual overlapping classes. Knowledge of these characteristics often proves helpful when deciding which font family to use in a special context (for further reading see, for example, the books [25, 42, 125] or the article [53]).

9.2.1 Monospaced and proportional fonts

Fonts can be either monospaced or proportionally spaced. In a monospaced font, each individual character takes up the same horizontal space regardless of its shape. In contrast, characters in a proportionally spaced font take up different amounts of space depending on their shape. In Figure 9.1, you can see that the “i” of the monospaced font occupies the same space as the “m”, while it is noticeably narrower in the proportional font. As a result, proportional fonts (also called typographical fonts) normally allow more words to be placed on a page and are more readable than monospaced fonts. The extra spaces around individual characters of monospaced fonts make it more difficult for the eye to recognize word boundaries and thus make monospaced text less readable.

However, monospaced fonts do have their uses. Within the proper context, they enhance the quality of the printed document. For example, in tables or computer listings where proper alignment of information is important, a monospaced font is a natural choice. In computer science books, it is common practice to display computer programs in a monospaced font to make them easily distinguishable from surrounding explanations.

9.2.2 Serifed and sans serif fonts

Another useful classification is based on the presence or absence of serifs. Serifs are the tiny strokes at the extremities of character shapes (see Figure 9.2). Originally they were produced by the chisel, when roman capitals were engraved into stone. For this reason, serifed fonts are often referred to as “roman” fonts.

Serifed fonts traditionally have been used for long texts because, it was argued, they are more readable. It was long thought that serifed letters give the eye more clues for identification. This is certainly true if only parts of the characters are visible, but for fully visible text more recent research has shown that reading speed is not substantially affected by the absence of serifs.

9.2.3 Font families and their attributes

Besides the crude classifications of serifed versus sans serif and monospaced versus proportional, fonts are grouped into font families. Members of a font family share common design principles and are distinguished by variations in size, weight, width, and shape. A member of such a family is often called a font face.

9.2.4 Font encodings

As mentioned in the chapter introduction, pdfTEX refers to the glyphs of a font by addressing them via 8-bit numbers. Such a mapping is called a font encoding. As far as LaTEX is concerned, two fonts having the same font encoding are supposed to be interchangeable in the sense that given the same input they produce the “same” glyphs on the printed page. To illustrate what happens if we use a font with an encoding not suitable for our input, here is the first sentence of this section again (using the Zapf Dingbats font):