Sub-Pixel Font Rendering: What is It?

For the past few years I’d heard the term “sub-pixel rendering” in various font and graphics related writings, and wasn’t really sure what the fuss was about. I finally read up on the technology and was surprised to find what a difference it makes in display clarity. The crux of sub-pixel rendering is using the three red, green, and blue elements that make up a single pixel to effectively triple the horizontal resolution of an LCD display. More resolution in the same physical space lets you show more data, and thus render more clearly. Wikipedia’s definition left much to be desired, however Steve Gibson has an outstanding page — and freeware utility — clearly explaining the subject. What doesn’t that guy know?

Know how sub-pixel rendering works, it’s easy to see how it could also be applied to graphics and gaming. Where an edge is computed, the resulting line could be shown more accurately (as far as the human eye is concerned) by rendering with respect to the sub-pixel elements of the display. Of course, the technology doesn’t work nearly as well on CRT displays, but for LCDs, it appears to provide ultra-crisp images and text. I wonder if Apple plans to make use of this awesome technology in the next revision of Mac OS X, or perhaps on the iPod and iPhone displays…

Sub-Pixel Font Rendering: What is It?

6 thoughts on “Sub-Pixel Font Rendering: What is It?

  1. RK says:

    Mac OS X does use sub-pixel rendering of fonts in Quartz; If you’re not seeing it, try adjusting the “Font Smoothing Style” in System Preferenes.


  2. Seems to me that Apple is already using it !

    Open TextMate, open a document with text that you can actually see, open the pref menu, go to ‘Font & Colors’, and in the bottom, uncheck (or check) “Anti Alias”.

    Than you will see that this is exactly what this site talks about.

    Then, if you have got the new Mouse utility from Apple, you are able to zoom on the screen with “command-scroll” and to see for yourself that every single text in Mac OS is written using colored pixels.


  3. Russ says:

    It’s already in Mac OS X 10.4.

    If you look in the Display preferences you’ll find the option. I think they call it font smoothing and you can select between CRT/LCD/Auto.


  4. Wow, I never knew that the “best for Flat Panel” font smoothing style was actually sub-pixel rendering! What I found most surprising, though, is that I don’t prefer it over “Standard – best for CRT,” which is plain old anti-aliasing. Take a look at this comparison image I put up on Flickr to see the difference between the two. While the screenshot can’t do justice for the crispness of sub-pixel rendering (it doesn’t capture the actual sub-pixels!), you will notice that the sub-pixel rendered text looks much bolder than the anti-aliased text. For that reason, I choose “best for CRT” whenever I configure a new Mac (LCD or CRT). I find that it’s simply more pleasing to my eye than a pseudo-bold font. I’m not sure if it’s the extra little colored blips around the edges of text that make it seem bolder or the relatively “large” pixels of my PowerBook compared to a high density LCD.

    One thing is for sure — more pixels per inch in LCDs really makes a difference, sub-pixel rendering or not. Comparing my LCD to that of a MacBook Pro, I found that LCD manufacturers packed in only about 50 more pixels horizontally, but 160 vertically, making up for the fact that sub-pixel rendering only works horizontally.

    Thanks for the insight and comments, guys!


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