Let Me Make One Thing Perfectly Clear[Type]

A lot of people misunderstand the way ClearType works -- especially when it is expected to help, and how. The following, written by Vista beta tester Clayton Macleod, provides a really good explanation of the issues (reprinted with permission!).

He also hits on points that Dean and I have raised before about problems with applications that "know better" about when to turn ClearType on, which can be idiotic, at times.

Anyway, I hope you find the text useful; I know it has helped others understand why they could not get ClearType to look good on their CRT no matter how they tuned it....

It [ClearType using a CRT] makes it look *different*, no question, and you may like the results, but it is not ClearType functioning as it is designed to.

The only way ClearType functions as it was designed to is on an LCD display where you can directly address each and every pixel/sub-pixel on the screen individually. It is practically impossible to address individual pixels on a CRT, there is no direct connection between the pixels on the face of the tube and the electrons causing them to light up.  In order for ClearType to work you have to be able to address pixels and their sub-pixel component red/green/blue colours independantly/individually.  This is how ClearType works.

ClearType takes advantage of the fact that on an LCD a single pixel is made up of three sub-pixels, the red/green/blue parts that make up one whole pixel, which you can control directly.  If you want to have only the red portion of the pixel at 100,150 light up with the blue and green portions unlit, you can do that, perfectly, every single time.  There's no chance in hell that you will have any idea what is actually lit up on a CRT.  You can control the signal you're feeding it, but that doesn't actually correspond directly to what is being lit on the CRT's face.

ClearType takes advantage of the fact that a pixel is actually split up horizontally into three sub-pixels. This is how it makes text sharper.  It ignores the fact that the three sub-pixels are red, green, and blue, and it just treats them all as grayscale pixels.  This means that your 1280x1024 pixel LCD is actually used as a 3840x1024 pixel screen when dealing with text.  This is how they make text appera so much sharper, because they're literally multiplying the horizontal resolution of the text by a factor of three.  They ignore colour and treat it as though they just have more pixels to use.  Again, the only reason that it works is because they can directly control each individual sub-pixel. You can't do that on a CRT, you just don't have anywhere near the same amount of control over the device as you do with an LCD, where you have direct control.

There's also the problem of sub-pixel group shape. Regular/classic-style CRTs have their red/green/blue sub-pixels grouped in a triangle shape, and Trinitron-style CRTs have their sub-pixels arranged in a horizontal fashion similar to LCDs.  But that doesn't mean that ClearType works as intended there, because you still have the humongous obstacle of degree-of-control to overcome, which nobody has.  So while you may not mind how ClearType looks to you on your CRT, it most definitely is not behaving as intended.  And that's because it's pretty much impossible for it to behave as intended.

If you're fine with how it looks, that's good for you, but it doesn't help the rest of us.  On every CRT I've ever looked at ClearType on it just looks blurry, because the pixels aren't defined anywhere near the way they should be.  On a CRT display, driven by a computer, it is very safe to say that any given single pixel that the computer is defining is being drawn on the CRT's face by multiple pixel groups.  The actual pixel groups of phosphors on the CRT's face are almost always much smaller than the computer's pixels they are drawing.  And so there are almost always a small group of CRT pixels being used to draw one computer pixel.  You're insanely unlikely to ever see a CRT using exactly one of its red/green/blue pixel groups to draw exactly one of the computer's pixels.

This goes against the design philosophy of ClearType about as much as you possibly could.  ClearType needs direct access to individual pixels/sub-pixels, period.  Without that, all you're getting is strange blurriness, typically with strange colouring around the edges of your fonts because of how the CRT is drawing the pixels.  It doesn't look anything at all like ClearType does when it is being displayed as intended on an LCD.

And no matter how much ground the LCD market has gained, is gaining, and will gain, the CRT market isn't going away anytime soon.  And that fact alone should be more than enough to give us a setting to completely disable ClearType throughout the whole OS and any apps running on top of it.  It doesn't work on CRTs, so I should be able to turn it off.  In XP, you can. The same setting in the same place in Vista does not do the same thing.  For some reason there is now a seperate setting in IE's options.  And even with those two turned off, you *still* get ClearType rendering in different sections of the UI.  It's idiotic.

'Nuff said!

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