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Easy reading

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[Times art: Bily Lampkin]

©New York Times, published February 14, 2000


Two software projects promise to make it easier to read type on computer screens by tricking the eye into perceiving subtle detail. You'll probably see it first in electronic books and handheld devices.

If anyone should know how hard it is to read from a computer screen, it is Dr. James Sheedy. A clinical professor of optometry at the University of California at Berkeley and founder of its Computer Eye Clinic, Sheedy has treated patients with computer-related eye strain for nearly 15 years.

So what does Sheedy do when he is faced with reading a jumbo-size e-mail? "If I have to read something longer than three or four pages, I prefer to print it out," he said. "What we're dealing with on our computer screens doesn't approach the quality of paper."

Uncounted billions of printed words have migrated to the computer, but few people would rather read on screen instead of reading on paper.

As the technological limitations of monitors become more apparent, attention has been shifting to software as the potential answer to eye torture. The two leading alternatives are ClearType from Microsoft and ClearView from Ductus. A variation of Ductus' technology is used in software produced by Adobe and others.

"In the past I don't think people seriously thought about what it takes to make things more readable," said Bill Hill, who led the typography group at Microsoft that developed ClearType. "People just naturally assumed this would be a hardware issue and things would get better."

ClearType will work only on liquid crystal display screens (LCD monitors are found mainly on laptops and handheld devices) and initially will be aimed at the electronic book market. And despite making its public debut more than a year ago, ClearType, which Microsoft says can improve text clarity by 300 percent, is not available to consumers and its technical details remain shrouded in secrecy.

Both ClearType and ClearView try in different ways to solve some of the problems that cause eyestrain. Sheedy says readers move their eyes in short spurts, up to five times per line. If the type is easy to read, the stops between movements are so rapid that readers suppress them in their minds and sense that their eyes are flowing across the text. If the type is not clear, the stops become longer and reading becomes more frustrating.

"The clearer the information is, the sharper it is, the better you're going to be able to absorb it," Sheedy said. "But if you have to struggle with each eye movement, that's going to slow you down."

Making that information clearer involves many factors, including the contrast between characters and background, the size of the letters, the spacing between letters, the ornamentation of the letters, the rate at which the screen flickers and the evenness of the image across the screen (a cathode-ray-tube, or CRT, screen tends to be brighter in the center).

The most obvious source of trouble is a lack of image crispness, called resolution. Even the best experimental monitors have a resolution of only about 200 dots per inch, far short of the 600 dpi generated by most laser printers. (While screen resolutions are technically measured in pixels, a dots-per-inch number can be generally considered to reflect the screen's pixel density.) As most computer users know, poor resolution becomes obvious when the size of the letters on the computer screen increases. As the character size typically used on monitors (9 to 12 points) grows, the formerly smooth-appearing letter A resembles a crude stack of children's building blocks.

But poor resolution at any size eliminates the subtleties of typefaces developed for the printed page. That situation was doubly frustrating for Hill at Microsoft, who abandoned the ink-on-paper world of journalism for digital imaging 14 years ago. "Typography has evolved for thousands of years -- it began even before the printing press -- to create shapes that are instantly recognizable," he said.

For example, Hill said, studies dating from the late 1920s showed that serif typefaces -- the slightly ornamented fonts commonly used for text in books, magazines and newspapers -- help guide readers' eyes along the page. Unfortunately, serif features on screen can be as small as 0.08 millimeters, too small to be displayed properly. Similarly, pixels are poor at rendering fine spacing adjustments between letters.

Hill and his colleagues at Microsoft turned their attention to trying to exploit the untapped potential of the LCD screen. Unlike the pixels on CRT monitors, those on LCD screens act like tiny shutters, either allowing or preventing light from fluorescent backlights to reach viewers' eyes. Every pixel on such a screen is divided into three subpixels -- red, green or blue -- that are turned on or off in various combinations to produce different colors. (The old Apple II employed subpixel technology on its CRT screen, and expensive high-resolution military LCD monitors use a variation of the idea today.) When all three are turned on at the same intensity, the pixel looks white. When all three are closed, the pixel looks black.

With ClearType, Hill's group treats each of those subpixels as a pixel in its own right, in effect tripling the resolution of the screen. "By addressing the subpixel, we could get text that was dramatically better to read," Hill said.

Beyond that, no one at Microsoft will say exactly how ClearType works because the company is still completing its patent application. But Steve Gibson, president of Gibson Research Corp. in Laguna Hills, Calif., has developed a similar product called Free and Clear that can be downloaded in demonstration form from his corporate Web site (www.grc.com).

"It's not a big mystery -- it's not a big breakthrough," Gibson said. (A Microsoft spokeswoman said ClearType did differ from Free and Clear but offered no details.)

In Gibson's program, pixels forming the white area immediately next to the edge of letters make themselves bigger by borrowing subpixels from their neighbors. Most LCD screens are arranged so that the subpixels where two pixels meet are complementary colors -- that is, when combined in correct proportions, they appear to be white. That allows a pixel set up to appear white to extend itself easily beyond its borders by stealing an adjacent subpixel. By carefully taking only complementary colors from next door, the pixel-and-a-bit creates in viewers' minds a much smoother white line between the letter and the background.

Like ClearType, Gibson's system works only on LCD monitors but not necessarily on all LCD monitors. On some models, the red, green and blue subpixels are arranged in a different sequence, so instead of creating crisp black letters, some monitors wind up showing letters encircled with annoying color fringes.

But if Jacobo Valdes, president of Ductus, has his way, ClearType will be only the second-most-popular solution. "Sure, it improves things," said Valdes, who formerly taught computer science at Princeton. "But it seems to me that's it's more a curiosity in that it improves things but in a very limited way."

Valdes would like to see subpixel tricks used only to fine-tune the positioning of letters -- another proven way to improve readability that is commonly used in print but largely impossible on computer screens. (Microsoft Reader, an e-book program to be released this year, will use subpixel technology to both handle ClearType and adjust letter positioning.) Not without self-interest, Valdes proposes that the clarity of text be improved by using anti-aliasing, a technology that Ductus licenses to Panasonic's parent, Matsushita Electronics, and Sun Microsystem's JavaSoft division. Matsushita uses the product for the difficult task of rendering complex Japanese characters on handheld screens, and Sun uses it for Java programming.

Rather than borrowing subpixels, anti-aliasing strategically turns adjacent white pixels along the edges of letters gray. When letters larger than about 20 points are viewed, viewers perceive the gray pixels as being black and fill in otherwise jagged edges. Unfortunately, with smaller letter sizes, the limited total number of pixels means that the gray ones become all too obvious. Rather than appearing sharper, the letters wind up looking slightly blurry.

Of course, screens with more pixels would eliminate that problem. Valdes says the problem vanishes on screens that can generate 150 dpi.

The world may have to wait a little longer for ClearType. It will first appear this year in Microsoft Reader, software designed for rendering text on handheld devices such as electronic books and palmtops and on PCs with LCD screens. While Hill has a laptop running a prototype version of Windows 2000 that allows him to work using ClearType, do not expect to find that feature in the version of the operation system that arrives in stores this week. The technology arrived too late to be included in the forthcoming software upgrade, Hill said.

ClearType has generated a lot of interest, especially among competitors. Adobe, which is planning its own e-book software, is evaluating the kind of technology Microsoft is using. Harold Grey, Adobe's group manager for type, said he thought the debate would go beyond narrow technical details.

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