Facts about figures: numeric styles with OpenType features

Over the past few months we’ve looked at a lot of different typographic techniques, approaches, and technologies. Before we get into the next big technical series (it’s high time we talk about font loading performance and management), I wanted to dial the focus back down into some finer details. Specifically I want to talk about OpenType features — but that can be a really big topic. So I want to start off right, and go by the numbers.

No, really: we’re going to talk about numbers.

Eyes wide Open(Type)

OpenType features encompass a whole range of elements within a typeface, from tiny details of spacing between specific letterforms (kerning), to alternate glyphs (an extra style of a lower case ‘a’ for example), to special connected characters called ‘ligatures’ (think of combinations like ‘ff’ or ‘fi’) and even glyphs for specific fractions. It can also include different styles of numerals. I thought this might be a good way to introduce the idea of OpenType features, how to use them on the web, and why you might want to do so.

On the case

There are a few different styles of numerals you may have come across. though it might not be immediately apparent that it is one style of several within a typeface design, rather than the design itself. The three we’re going to look at are Lining and Old Style Figures, and Tabular (as opposed to Proportional) spacing. Here are the differences between them: