Font Basics

A font, also known as a typeface, is a collection of characters, such as letters, numerals, punctuation marks and other symbols, that possess common design characteristics. Each character in such a font is described in the same way as a graphic, either as a bitmap or as a vector image.

A bitmap font is usually limited to the resolution of a computer’s monitor, typically 72 dpi for the Mac OS or 96 dpi for the Windows system, both of which are inadequate for printing. Unfortunately, such fonts become distorted when resized. For example, a 12-point bitmap font when expanded to a 24-point size appears to have half the resolution, making it look very jagged.

A vector font, on the other hand, isn’t designed for a specific resolution, which means that it looks good at any size. However, vector fonts also require more computer processing, which means that some operating systems retain bitmap fonts, also known as screen fonts, for on-screen presentation, whilst using vector fonts for printing. Unfortunately, this can worsen the inherent disparity in character positioning that can occur between text on the screen and that produced on paper.

• The relatively poor resolution of a monitor can make fonts appear distorted.
• In the Mac OS, each font shown in the Font menus is a font family. For example, Geneva actually contains 96 font faces, including 16 combinations from the Style menu and at least 6 font sizes. The system sometimes creates such variations by modifying the Plain font.
• The size of a font is measured in points, where one point equals around ¹⁄72 of an inch.

Various file formats are used to describe a complete font as vector graphics. Although some of these are more common on specific computer platforms, they’re not mutually exclusive. For example, the Mac OS lets you use both TrueType and PostScript fonts at the same time.

PostScript (Type 1) Fonts

PostScript fonts, as developed by Adobe, were introduced to the Classic Mac OS alongside the Apple’s first LaserWriter printer, and later appeared in the Windows system. Unlike TrueType, these fonts always employ separate vector information for each typeface within a font family, thereby providing the high-quality required for professional desktop publishing (DTP) work.

• PostScript fonts can only be reproduced properly on a PostScript printer, or on a non-PostScript printer alongside software known as a raster image processor (RIP).
• In theory, you can encounter PostScript fonts in Type 0, Type 1, Type 3, Type 4 and Type 42 forms. In practice, virtually all modern applications only use Type 1 fonts.

TrueType Fonts

This format, originally devised by Apple, was introduced to the Classic Mac OS following the arrival of PostScript, although it later migrated to Windows. It allows high-quality fonts to be reproduced on a non-PostScript printer, providing thousands of characters and allowing any degree of resizing.

• In theory, the results produced by a TrueType font aren’t as good as those created by the equivalent PostScript version. In practice, it’s difficult to see the difference. Sadly, PostScript devices often suffer from technical problems, so you may prefer to use TrueType.

OpenType Fonts

This modern format, developed by Microsoft and Adobe for use on Windows, Mac OS and other computers, is designed to replace the older systems described above. With OpenType, applications can adjust the shape of characters or replace selected symbols by swashes. Similarly, specified groups of characters can be replaced by ligatures and artificial fractions can be replaced by true fractions, assuming the latter exist in the font. The format also supports alternate glyphs.

The information for each font is kept in an OpenType Font (OTF) file, which is identified by an .otf filename extension: such files can contain a TrueType or PostScript font description, or both. Unicode character coding is used, accommodating up to 65,000 different characters for world languages: rather better than the PostScript Type 1 format that only allows 256 characters.

• A standard edition OTF file often contains the same number of characters as an equivalent PostScript file, whilst a Pro version usually has the full Unicode character set.
• The first OpenType fonts to be produced were Adobe Garamond Pro, Adobe Caslon Pro and Caflisch Script Pro, as well as two Japanese fonts.

Each OTF contains embedding permissions that determine how the font can be embedded into certain documents, such as a PDF or EPSF file. The permissions are as follows:-

TrueDoc Fonts

This system, developed by Bitstream, employs similar technology to OpenType, but is specially designed for Netscape, the popular Web browser for the Internet.

• TrueDoc fonts are in Portable Font Resource (PFR) files, with an extension of .pfr.

Cross-Platform Issues

Most modern applications are available in versions that can be used on various kinds of computers. In addition, the documents that they produce can be transferred between different machines whilst maintaining the correct character set and line endings.

The actual fonts used in your work aren’t conveyed inside such documents, mainly because this would make the files far too large. Instead, the available fonts form part of each machine’s operating system. The fonts that you employ are then identified by a list of font names stored in each document.

Incorrect Fonts

Unfortunately, there isn’t a standard set of fonts used on any computer, let alone across different operating systems. At best, this means that a document can end up with the wrong fonts, resulting in incorrect line wrap and text positioning, as well as a different appearance. At worst, none of the fonts are recognised, making it difficult to restore the original look of the document.

• Apparently, the PostScript fonts for Helvetica and New Century School Book are identical for Windows and the Mac OS. Try this yourself, the next time you transfer files!

Some applications, such as Adobe Reader (Adobe), incorporate a font substitution system that replaces any missing fonts by generic fonts that have a similar appearance. Sadly, there are few other programs with this feature. However, in HTML documents, as used for Web pages, you can include a list of suitable fonts, as in this example from a Cascading Style Sheet (CSS) file:-

which means that the recipient’s computer first looks for the Geneva font. If this is missing it then looks for Verdana. Failing both of these, it’ll use a generic font with a san-serif style.

Font Names

The Mac OS and Windows operating systems employ fonts that have different names. The following table shows the nearest equivalents for the most common fonts used in each platform:-

Screen Resolution and Font Size

Mac OS is designed around displays that have a resolution of 72 dpi or ppi, whereas Windows is based on 96 dpi. Hence font sizes can appear differently, as shown in this table:-

©Ray White 2004.