ClearType

ClearType attempts to improve the appearance of text on certain types of computer display screens by sacrificing color fidelity for additional intensity variation.

It was then analyzed by researchers in the company, and signal processing expert John Platt designed an improved version of the algorithm.

[4] Dick Brass, a vice president at Microsoft from 1997 to 2004, complained that the company was slow in moving ClearType to market in the portable computing field.

In a MSDN article, Microsoft acknowledges that "[te]xt that is rendered with ClearType can also appear significantly different when viewed by individuals with varying levels of color sensitivity.

"[6] This opinion is shared by font designer Thomas Phinney (former CEO of FontLab, also formerly with Adobe Systems[7]): "There is also considerable variation between individuals in their sensitivity to color fringing.

Anecdotal evidence suggests that some people are fine with Method C when reading continuous text at 96 dpi (e.g. Times Reader, etc.)

The study notes that maximum benefit may be seen when the information worker is spending large proportions of their time reading text (which is not necessarily the case for the majority of computer users today).

"[16] A 2007 survey, of the literature by Microsoft researcher Kevin Larson presented a different picture: "Peer-reviewed studies have consistently found that using ClearType boosts reading performance compared with other text-rendering systems.

In a 2004 study, for instance, Lee Gugerty, a psychology professor at Clemson University, in South Carolina, measured a 17 percent improvement in word recognition accuracy with ClearType.

Similarly, in a study published in 2007, psychologist Andrew Dillon at the University of Texas at Austin found that when subjects were asked to scan a spreadsheet and pick out certain information, they did those tasks 7 percent faster with ClearType.

[18] Because ClearType utilizes the physical layout of the red, green and blue pigments of the LCD screen, it is sensitive to the orientation of the display.

A Microsoft ClearType tuner utility is available for free download for Windows versions lacking this facility.

ClearType in WPF supports sub-pixel positioning, natural advance widths, Y-direction anti-aliasing and hardware acceleration.

DirectX 10 cards will be able to cache the font glyphs in video memory, then perform the composition (assembling of character glyphs in the correct order, with the correct spacing), alpha blending (application of anti-aliasing), and RGB blending (ClearType's sub-pixel color calculations), entirely in hardware.

Caching these partially rendered glyphs requires significantly more memory (Microsoft estimates 5 MB per process).

As pixel densities of displays improved and more high DPI screens became available, colored subpixel rendering became less of a necessity according to Microsoft.

Also Windows tablet user interfaces evolved to support vertical screen orientations where the LCD color stripes would run horizontally.

The original colored ClearType subpixel rendering was tuned to work optimally with horizontal orientation LCD displays where RGB or BGR stripes run vertically.

[33][34] Many Office 2013 apps including Word 2013, Excel 2013, parts of Outlook 2013 stopped using ClearType and switched to this DirectWrite greyscale antialiasing.

The reasons invoked are, in the words of Murray Sargent: "There is a problem with ClearType: it depends critically on the color of the background pixels.