iPhone Sub-Pixel Anti-Aliasing and Screen Rotation

Steve Weller:

But there is a very simple reason that sub-pixel is not used on the iPhone: screen rotation. Sub-pixel anti-aliasing relies on the increased spacial density in the horizontal direction of the individual color bars (and on the pathetic color-resolution of eyes). Once you switch vertical and horizontal by rotating the screen, this no longer works and you have no option but to have a high-enough pixel resolution to make simple anti-aliasing work well.

I’ve received a slew of emails from readers pointing out the same thing, and it does make sense. But: I tested it on my Cinema Display with the screen rotated 90°, and, to my eyes, sub-pixel anti-aliasing still looked good. So I’m not sure the iPhone’s rotating display is reason enough to rule out sub-pixel rendering.

★ Sunday, 2 December 2007