iPhone 5 Rumors Heating Up, Point to 4-inch Screen, HD Camera
The folks over at Apple Insider obtained a research note from KGI analyst Mingchi Kuo, and according to Kuo, Apple is most definitely switching from a 3.5-inch 4:3 display to a 4-inch 16:9 screen. It will be an IPS screen, and it will measure precisely 4.08 inches, Kuo says, with an 1,136x640 resolution and 500 nit brightness.
If Apple switches to a 4.08-inch display with a 1,136x640 resolution, existing apps would work just fine, albeit with black bars on either side.
Why not go even larger? After all, the jump from 3.5 inches to 4.08 inches, while noticeable, isn't overly dramatic. But the reason why Apple apparently decided against a 4.3-inch or 4.5-inch screen is that such devices are, in Apple's opinion, difficult to operate with one hand. There's also the concern of backwards compatibility with existing iPhone apps and battery life to take into consideration.
Since the horizontal resolution of the display would be the same, Kuo says app compatibility is one thing Apple can check off its list. Existing apps would simply make use of letterboxing with black bars on either side