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Description of ClearType Font Smoothing Technology in Windows XP
Article ID: 294851 - View products that this article applies to.
This article was previously published under Q294851
This article describes ClearType, Microsoft's implementation of font-enhancement technology that is capable of making fonts appear clearer on liquid crystal display (LCD) screens.
ClearType is a form of sub-pixel font rendering that draws text using a pixel's red-green-blue (RGB) components separately instead of using the entire pixel. When the pixel is used in this way, horizontal resolution theoretically increases 300 percent.
Picture elements on an LCD screen are actually comprised of individual horizontally oriented red, green and blue sub-pixels. For instance, an LCD screen that has a display resolution of 800 x 600 pixels actually has 2400 x 600 individual sub-pixels. The human eye is not capable of differentiating colors on such a small scale, so a combination of these three primary colors can emulate any intermediate color. Sub-pixel font rendering takes advantage of this by antialiasing at the sub-pixel level instead of at the pixel level.
Because a standard cathode-ray tube (CRT) screen uses an electron beam to excite pixels, and does not have specific pixels at a specific location, you do not experience the same benefits that you experience on an LCD screen when you use a CRT screen. However, because ClearType still includes antialiasing support, you may see some improvement when you enable ClearType on a CRT screen.
For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/294847/EN-US/ )ClearType Does Not Work with Magnifier Enabled
(http://support.microsoft.com/kb/306527/EN-US/ )HOW TO: Use ClearType to Enhance Screen Fonts