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If I understood correctly, subpixel rendering was originally designed to improved anti-aliasing of text on LCD screens. It makes use of the fact that each pixel on a color LCD is actually a bunch of individual red, green, and blue subpixels and does some magic with them to make text sharper. The physical properties of a CRT display is quite different. So, does subpixel rendering still work on CRT displays?

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up vote 14 down vote accepted

Not as such. The results vary from screen to screen between "blurry mess" to "nice and clear".

Most computer monitor CRTs have a shadow mask which has a triangular arrangement of colors.

enter image description here

Here there is clearly no way that subpixel rendering can work the way it should. However, you still get the difference in brightness and CRTs being blurrier than LCDs may make the text appear similarly to conventionally-smoothed text (which uses just grayscale to smooth the edges).

Some computer screens have an aperture grille and I happened to use one of those for several years.

enter image description here

Here you can actually have a similar effect as on LCD screens for ClearType, especially when hitting the maximum resolution of the display (I tended to do so because my eyes work and I valued the space on screen :)). However, there is no guarantee that every pixel will lie exactly at the boundaries you would like it to lie. Also with older monitors the dimensions of the image tend to vary with overall brightness of the image. But at least for me subpixel rendering on such a screen was superior to grayscale antialiasing.

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Good explanation. ;-) – GeneQ Jul 23 '09 at 15:02
+1 - I wondered why everything I read always said that ClearType didn't work on CRTs, when it looked great on the CRT I used to usse. – phenry Jul 23 '09 at 15:07
I am unaware of any CRT display ever having sufficient precision or sharpness to address individual phosphor dots. Instead, the beam is deliberately made diffuse enough so that it's always hitting more than one set of phosphor dots at a time. If it weren't, it would be necessary to calibrate many parameters associated with scanning to within a tenth of a percent; it might be theoretically possible for a continuously-self-calibrating system to manage that, but I'm unaware of any having been designed to do so. – supercat Nov 16 '14 at 22:21

When I used a 17" CRT on it's maximum resolution (1280*1024), I enabled subpixel rendering and it actually looked better.

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Me too! A few years (maybe a decade) ago I tried it on my 14" CRT and indeed the text looked much better – Lưu Vĩnh Phúc Sep 18 '13 at 6:33

Sounds like it kind of works but not nearly to the same effect as the LCD screens.

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It depends. If you ask two people about the difference between MP3 and a FLAC you will get vastly different results - it depends how fussy you are.

Technically you should get color bleeding instead of clean edges; but chances are you wouldn't notice it. Especially if the dot pitch is low enough - which CRTs are good with these days.

Back in the stone age when I used CRT I enabled it and as Daniel said the quality was better, for me at least. I saw absolutely no color bleed (even on a crappy $80 CRT at that) and had reduced eye strain.

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Although ClearType was not designed specifically for CRTs, but years ago, I tried enabling ClearType on my CRT and it greatly improved text quality than before. But the effect maybe less than LCDs because the difference in pixel layout. This is what Microsoft said:

Q. Will ClearType improve text display on CRT monitors?

A. Yes, but less so than with LCD displays. Because a standard cathode-ray tube (CRT) screen uses an electron beam to activate pixels, ClearType does not provide the same benefits that you experience on an LCD screen. However, because ClearType still applies a form of filtering similar to traditional antialiasing, you may see some improvement when enabling ClearType on a CRT screen.

More specifically, the ClearType technology is optimized for LCD panels with red, green, and blue (RGB) striped sub-pixels that are oriented vertically, although it performs reasonably well on CRT displays (especially those that are aperture grille based) and even LCD panels with horizontally oriented RGB stripes. Although this might seem counterintuitive, through informal studies, we’ve found that about 70% of users prefer ClearType even on these non-optimal displays. Of the 30% who preferred other rendering techniques, their biggest concern with ClearType in these non-optimal cases was the loss of text contrast.
... Even though there were still CRTs in use, feedback from Windows XP customers was positive on the quality of ClearType rendering on CRTs. After we made the choice, the feedback on the decision to enable ClearType as the default for Windows Vista was overwhelmingly positive.

To get the full benefit of ClearType, you need a high-quality, flat-panel monitor, such as LCD or plasma. Even on a CRT monitor, you might get some improvement in readability with ClearType.

If that doesn't work for you, you can try Mactype which has a profile for CRT rendering, or you can create your own profile

mactype profile

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