The way to get the best out of anything is to understand it as fully as possible.
You’re unlikely to ever delve into the innards of an OpenType font, but knowing how it works can help you get more out of it where it counts: in your own documents.
OpenType fonts can contain thousands of different characters - or, to be more precise, glyphs. These are the elements which make up what we call characters. In western languages these are effectively the same thing, but with the more complex alphabets of others they are often combined according to complex rules to create the final items. Glyph substitutions, where a character can be substituted for another one in different circumstances, can happen in a number of different ways, from simple to complex, based on adjacent characters, language setting, OpenType feature settings, and more.
OpenType allows glyphs to be both positioned and substituted for other glyphs in a number of different ways. The information that defines what a particular glyph does in specific circumstances is stored within the font itself. This could cover a number of different things based on the settings specified in the current application; it is the user’s application which is generally responsible for choosing what settings are applied.
As Dean Allen, the writer of the Textism blog, put it two years ago (see www.textism.com/article/713), the PostScript Type 1 format is only marginally more useful than if it was “chiselled onto the arms of a manual typewriter”. Sure, this viewpoint is extreme, but it does highlight the basic flaws inherent in our ‘tried and trusted’ type formats. Traditional PostScript and TrueType fonts are dumb; they have zero ability to adjust characters or glyphs according to context, and the 256 character restriction limits what can be stored in a single typeface file.
What OpenType makes possible is having a single font file which contains absolutely everything needed to set information in that typeface, whatever the language, coupled with the ability to adjust what you get according to a rich set of context-sensitive rules built into each font. A single font of this kind has 64,000 character slots rather than just 256, and the format even allows for 16 different ‘planes’ of 64,000 character arrays to be stored within a single font file. Sounds daunting? Fortunately, what makes OpenType tick is its built-in intelligence. When used in the right applications, your typeface will give you the characters you need by choosing the most approproate character glyphs as you type. In most cases you just have to choose it in your application’s font menu and carry on as normal, and exploiting it further in key applications is done with a few simple menu choices.
As the format is fully cross-platform it doesn’t matter whether you use a Mac or a PC; the file is exactly the same, so you don’t have to worry about that aspect when shopping for new faces. But you don’t have to shell out to get started; you already have a number of OpenType fonts on your Mac, courtesy of your Mac OS X installer. Not all fonts installed with Mac OS X are OpenType models, but the following ones are, offering stylistic and linguistic finesse to anyone that puts them to work.
The following is a list of some - not all - of the OpenType fonts which ship as standard in Mac OS X, as of OS X 10.4:
Times New Roman