OpenType is a font technology that was co-developed by Adobe and Microsoft. Its specs were published in 1997 and the first fonts became available in 2000. OpenType fonts resemble TrueType fonts but they can contain either TrueType or Type 1 font data. As such, they are a merger of two competing technologies.
These are some of the advantages of OpenType:
- OpenType supports Unicode: fonts can contain large character sets of up to 65,000-plus characters, including all Western characters and accents as well as non-Western (e.g. Japanese or Chinese) characters. To make use of such large character sets, one needs an OpenType font that actually contains all of those characters, an operating system that supports Unicode and an application that provides access to the character set (e.g. for QuarkXPress you need version 7 or later, all versions of InDesign support Unicode, for Corel Draw you need release 12,…)
- Better typography: OpenType fonts can contain a wide range of glyphs (character shapes) which includes:
- old style numerals
- titling caps
- historical characters
- swash characters
Such characters are often unencoded: they are present in the font but not directly accessible for the user. A special routine has to embed the glyph. For instance: if the word “flux” is used in an InDesign document and uses the appropriate OpenType font, InDesign replaces the “fl” characters by the much nicer “fl” ligature. So to make use of a lot of the advanced typographic features of OpenType, you need to use a software application that supports them. The CS versions of InDesign and Illustrator as well as QuarkXPress 7 do but CorelDraw 12 for instance doesn’t offer this yet even though it ships with 1000 OpenType fonts.
- OpenType fonts can be compressed efficiently. Smaller font file sizes make it easier to embed fonts in files. This is useful for both PDF files and web pages. The compression technique that is used depends on the type of OpenType font. Adobe Compact Font Format (CFF) is used for PostScript OpenType fonts. Agfa MicroType Express is used for TrueType OpenType fonts. Despite the use of an efficient compression algorithm, OpenType fonts can still be much larger than other fonts because of the additional information and glyphs. For example, the Adobe OpenType Pro fonts range from 70 to 210 KB per face, averaging around 150 KB per face. Palatino Linotype, an OpenType font that ships with Windows 2000 has four faces ranging from 362 KB to 506 KB. The latest version of Arial ranges from 200 to 284 KB. There is however an Arial Unicode version which weighs in at 24 MB!
- OpenType fonts can contain multiple optical sizes within a font family, so that type in various point size ranges can be based on separate sets of character outlines, for finer display type and sturdier characters in small sizes.
- Improved kerning: letters with similar shapes (the left sides of c, e, and d, for example) or a single letter with a number of different accents (e.g., À, Á, Ä) can be kerned identically. This reduces the size of kerning tables and extends the number of letter pairs that are kerned.
- As with Truetype fonts, OpenType fonts store all data in one single file.
There are currently over 10000 OpenType fonts available. The past years both operating systems and applications have improved their support for the advanced features of OpenType. It is clear that OpenType is the font format of the future.