Microsoft's ClearType
By Richard Leader

There is a lot of hype concerning Windows XP's new image quality feature, ClearType, which is purported to be a tremendous advance in the way fonts are displayed on screen. While not nearly as radical as Apple's OS X and its Quartz display (which renders things internally as vectors, not bitmaps, meaning that figures are always as mathematically smooth as can be depicted externally with square pixels), from Microsoft's touting of the ClearType feature, one might think that font smoothing is entirely new to Windows platform. In a sense it is. Though a standard font smoothing technology has been included with every Microsoft operating system for over half a decade, the feature was turned off by default as it tended to marginally lower overall performance at a time when computer's speed was measured in megahertz and not gigahertz--though any effect on today's machines is negligible, which makes the still standard default "off" setting all the more questionable.

Font smoothing on a pre-Windows XP system takes only seconds to enable though most users are unaware of the option. In your display settings (most easily accessed by right clicking on a blank section of your desktop wallpaper and selecting "properties" from the drop down menu) all that is required, is to simply activate the "effects" tab and check the box that says "Smooth edges of screen fonts" and click "ok" to finalize the setting.

ClearType is an evolved form of the standard method of font smoothing which utilizes anti-aliasing. While the term "aliasing" is actually borrowed from technology that has more to do with sound and defies easy definition, it has popularly been replaced by "jaggies" or "pixilation" in the common vernacular to describe when square pixels begin to limit the attractiveness of a computer display. Anti-aliasing is a process used to eliminate these jaggies by finding creative ways to use color to make a pixel appear to be more than one color at a time (which they cannot be, by definition) by blending it to new color that is partway in between the colors of the two objects that border it.

Cleartype also positions itself as a superior display method for flat liquid crystal displays (LCD) that notebooks are equipped with (though they are gaining ground in the desktop market as well) as they display images differently than conventional CRT monitors.

LCD screens utilize bands of primary colors and ClearType takes advantage of that in the rendering of fonts, as it can effectively use only 1/3 of a pixel on either side of a line, for a much smoother image compared to standard font smoothing--but only on LCD screens.

If you examine the above image, imagine a cluster of vertical red, green, and blue lines as being a single "pixel." When all three are lit the effect displayed is white, while when all three are dark the result is black, with various other colors depicted with different levels of each. ClearType on an LCD screen allows a character to actually be thinner than a pixel, a feature which is extremely useful when you have only a limited number of pixels to work with (and is a highly touted component of Hewlett Packard's latest personal data assistant or PDA, the Jornada, which features a small color LCD display).

That does not mean that ClearType is not without benefit for those of us with aging traditional monitors. You can examine the difference yourself in this head to head comparison of ClearType and "standard" font smoothing on a Windows XP display at 1280x960 pixels. Fonts are New Times Roman and Arial; smallest font size is 5pt., for scale; file PNG format for exact representation.

The first thing you probably noticed is the colored fringe on the ClearType 2X enlargement. The fringe on the left side of the "A" is red, while the other is blue, mirroring the way LCD screens display images (on a LCD, each of those fringes would be nearly 2/3 thinner, as the red columns are on the left, blue on the right). In the magnification, the colors are jarring--especially so if your video card is set at a higher color saturation than normal, such as if it supports "Digital Vibrance" (nVidia based cards) or an equivalent setting from another manufacturer. The physical distance of pure black from white on the color chart is one of the most dramatic problems in anti-aliasing (because color inevitably seeps into the grays that make the steps in between) so this shimmering effect will be less pronounced on other color combinations of text and background.

The second thing you noticed, I would wager, was the fact that the standard font smoothing just up and quit once the font size shrunk past a certain point. This is the prime advantage for the ClearType rendering method, as it seems to be slightly less effective at the larger sizes and incapable of eliminating all the jaggies.

Not only are the smaller fonts better looking they are also legible at a smaller size. As websites get more complex, more designers are locking their fonts at a certain size with cascading style sheets (CSS) to keep tables and columns of text and graphics in line, rather than "exploding" if a viewer's browser prefers a larger size. Many of these font sizes (including the ones on this page) are underneath the minimum required to engage standard font smoothing which seems to be dependant upon screen resolution.

Here is my page displayed (1280x960) with standard font smoothing--which is quite evidently not doing anything--and ClearType.

Whether or not standard font smoothing is enabled for a certain size character seems to be dependant upon screen resolution. These seem to be the smallest size character to be smoothed on various popular resolutions:

This data set is problematic as only 1600x1200 is capable of smoothing 10pt. fonts, which should be considered the realistic small to average size character that web designers are creating their pages to be read at. While nearly all video cards today can display 1600x1200, few mainstream monitors can sustain a high enough refresh rate to make that resolution comfortable to use, let alone readable on anything less than a 19" monitor. The minimum font size for standard smoothing for 1024x768 and 800x600 are shameful--it would be rare to encounter a font that large during normal web browsing that was not created as a bitmap image to begin with. 640X480, on the other hand, seems to be doing things right and I cannot imagine why the other resolutions are not following its lead.

What this means practically, is that if your computer is set at an extremely low resolution of 640x480 (which is no longer available in Windows XP) or at an extremely high one of 1600x1200 or above, standard font smoothing is likely to be more attractive on your CRT display because of the absence of colored fringes and smoother large characters. For the rest of us at the center of the bell curve, ClearType is the only way to go.

If you have Windows XP, to enable ClearType, you must do the following:

Right click on your desktop and select "properties" from the drop down menu.

Click the "appearance" tab at the top and select "effects" from it.

Make sure that the box "Use the following method to smooth screen fonts" is checked and that ClearType is selected in the associated drop down menu.
Click "ok" and exit both menus to save your settings.

What is commonly not known among those who use ClearType is that the anti-aliasing effect is customizable. Easily accessed through the web at

http://www.ntcompatible.com/faq37.shtml

there is a display for selecting the setting which is most visually appealing to you. More convenient, however, are a variety of freeware programs such as ClearTweak.

ClearType is nearly perfect for users of LCD screens, of that there is little doubt; it is also generally a good solution for conventional monitor owners as well, because of the increased readability of small fonts--though it takes some time for most users to adapt to it (it can often seem blurry at first). While not quite the revolution that Microsoft wishes to market it as, it is a great evolution of an existing technology and a welcome option.