Yesterday, a friend of mine posted a twit remarking that font smoothing in Windows 7 was not done properly and how Microsoft still hadn’t gotten it right. I hadn’t noticed any obvious issues of this nature in my usage and testing on Windows 7, so I was instantly curious to know why he thought as he did and if Microsoft, after all these years, still hadn’t mastered something as simple as font smoothing. So I set out to do the research.

Joel on Software has a great article thoroughly explaining the reasons behind the differences, but for those who want the digest version, I’ll give it to you here.

Apple and Microsoft use the same process for rendering fonts, a technology called “sub-pixel rendering.” The reason the two operating systems render text differently (specifically in web pages) is due to the algorithm behind the font rendering engine. Each character within a font is set to take up a certain amount of space measured in pixels–thus an “A” takes up more horizontal space than, say, an “I.” In addition to that, each typeface has it’s own style of letterform–that is each letter is designed to look a specific way and may, in some cases, slightly exceed the given letter-space when font smoothing is applied.

Apple, the company with a philosophy that the artistic and stylistic aspects of just about anything trumps everything else, wrote their font smoothing algorithm to allow type to exceed it’s allocated space, giving fonts more character at smaller sizes. This makes for a smoother looking font, but also is sometimes blurry and can be hard on the eyes. Microsoft on the other hand took a more practical approach and decided that each character must fit exactly within the available space and therefore “chisels” the characters to fit within that space. This creates a less-smoothed font, but makes things far easier to read on-screen. In fact, you can see this difference directly on a Windows machine by putting a Safari for Windows window and an Internet Explorer or Firefox window side-by-side. You’ll see what I mean.

So the question is now: Which company is correct?

The short answer is both. Apple’s OS will provide a more unified look between computer screen and printed output. This is yet another reason (whether they realize it or not) why designers often prefer OS X over Windows. Microsoft gives users a more readable on-screen experience at the expense of some character style (although at large font sizes, these differences become less noticeable.

All-in-all it’s pretty much just a matter of personal preference. Neither way is necessarily wrong–it’s all about what you like.