Posted by Christopher Slye
A month ago, Typekit rolled out improved font rendering on Windows, and began serving certain typefaces in OpenType CFF (PostScript Type 1) format*, instead of the more customary TrueType format. Yesterday, they began serving selected Adobe Web Fonts as CFF as well, and the result is noticeably better appearance for large text sizes.
Typekit observed that, although TrueType fonts tend to look better at text sizes with Microsoft’s ClearType subpixel antialiasing in Windows GDI rendering environments (still the majority of web viewers out there), there can be distracting pixelation on some diagonal features at large point sizes. Their clever solution is to serve CFF fonts for certain display designs which are unlikely to be used at smaller text sizes. GDI will only apply grayscale antialiasing to Type 1 fonts, resulting in smoother appearance. On Mac OS X and in some newer Windows environments (DirectWrite, to be more specific), the quality is essentially the same as TrueType.
Here at Adobe, we’re obviously pleased to see CFF fonts served where it makes sense to do so. We think CFF has certain qualities and advantages which often make it a better choice — on the web and elsewhere. (Later this month I will be speaking more about this at the ATypI conference in Reykjavíc, Iceland.) To read more on this subject from Typekit and to see more examples, see yesterday’s post on the Typekit Blog.
* When referring to “PostScript,” “Type 1″ or “CFF” fonts, what I really mean is OpenType with this outline format in it. OpenType fonts can contain outlines in either CFF or TrueType format. CFF — the Compact Font Format — is a variation of the original Type 1 font format, created by Adobe along with the PostScript language.