David Weinberger
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The visual display of knowledge

01 March 2000

Computer displays suck. Anything else is a euphemism. (Oh, OK, I'll use the technical term for computer display quality: They exhibit suckitude.) Even your swell, new, 21-in. flat-screen beauty is totally inadequate for its main job: displaying text. Small type is unreadable, and large type has all the clarity of a newspaper read through a screen door. If computer displays were capable of displaying readable text, not only would your time on line be more pleasant, but you might actually consider reading long documents on your computer. And that in turn would make electronic book publishing feasible, unleashing the same market forces as MP3 has set loose in the music publishing world.

There is a standard that begins to make good on the promise. It's called ClearType and, gulp, the trademark belongs to Microsoft.

The idea behind ClearType has a pedigree. In fact, you could claim that Steve Wozniak invented it in 1976 to increase the horizontal resolution of the Apple II's high-resolution graphics system. But, hey, what's a patent among friends? Besides, Woz (as his friends call him, or so I'm told by people who are even less his friend than I am) was designing for non-digital displays, whereas ClearType only works on LCDs.

You see, your LCD screen consists of color triads. When you see a white pixel, you're actually seeing a red, green and blue sub-pixel. (Yes, I know that mixing red, green and blue should give you a brown about the color of where you spilled your Starbucks on your aunt's walnut credenza. You're thinking about mixing cooking ingredients, but LCDs mix light, and since black is the absence of color, white must be the fullness of color. You can prove that by shining a very bright light in your eyes and noticing that you close your eyes and thus see black. That was explained to me by Roy G. Biv.) So, it takes three sub-pixels to make one pixel.

ClearType displays type by managing the individual sub-pixels, tripling the effective resolution of your screen. Pretty damn clever, eh?

Having more and smaller dots to play with lets the computer display better looking type. Font rendering software takes the information that's included when you install a new font (A Times Roman "I" is a straight vertical line with two horizontal lines at the ends, sort of) and transforms it into instructions for turning on a set of colored pixels ("I want 12 pixels in a vertical row," etc.). Normally, font rendering software has to make some pretty ugly decisions when figuring out how to put a particular letter on the screen. For the sloping parts of the letter, it only has big (pixel-size) blocks to use, so you get jaggies. For parts of the letter that should be especially thick or thin (say, the different legs of the letter "m"), it only has one size block to play with so sometimes it wants to make a leg 1.5 blocks thick but must round it off to either one or two blocks.

That's why our eyes hurt when reading text on a screen: rounding errors.

Font rendering software mitigates some of the effects of the coarseness of pixels through anti-aliasing, which rounds off the edges of jaggies by turning on gray pixels around the stair steps. ClearType achieves a better result by using colors instead of gray and, more importantly, by having smaller blocks at its disposal.

The results are impressive, and better seen than described. Steve Gibson (Gibson Research) has put up a great site that explains all this stuff in readable, friendly prose, with pictures. And he's included a 35K downloadable program that demonstrates ClearType vs. OrdinaryType on your LCD screen. (See Web addresses at the end of this article.)

But there are some limits. First, ClearType only works for black-and-white text; no pixels are left over for rendering color. Second, it only works on LCDs, although on desktop monitors it can give roughly the same effect as anti-aliasing. Third, it only increases horizontal resolution because the sub-pixels are arranged horizontally. Fourth, it's from Microsoft. Fifth, it's still not good enough to make you think you're reading ink on paper.

The Beast of Redmond announced on Jan. 6 that ClearType will be part of its new Pocket PCs (Motto: "Keep your Palms out of your pockets"), meaning that the next convergence won't be of PDAs and phones but PDAs and books. Or so Microsoft would like.

ClearType is an intermediary step that will make your text-based knowledge literally clearer. We still wait for the day when the back of the display problem is broken and we have cheap, webbed, portable reading devices that are as crisp as ink on paper, but with color and multimedia. That's the point at which working knowledge--intimately tied to its expression--will be redefined.

Relevant Web sites:Steve Gibson's ClearType resources page Microsoft on ClearType Microsoft press release;

or download Steve G.'s demo software

David Weinberger edits The Journal of the Hyperlinked Organizatione-mail [email protected].