What is the Apple iPhone 4 Retina Display?
As we know, the retina is comprised of light-sensitive tissue at the back of your eyeball and collects sensory information that ultimately forms what we see. Apple is hinting at the fact that the high number of pixels per inch (326 ppi) exceeds the capabilities of the human eye at 10-12 inches.
Because you're not capable of seeing more than 300 or so ppi at this distance, text on the iPhone 4 screen has the same quality as a printed page. No graininess, pixels or jagged edges are visible.
The specifications of this specially-engineered screen exceed anything currently on the market in a smartphone. The screen is the same size as the iPhone 3GS screen, however it has four times the number of pixels. Each pixel in the Retina Display is only 78 micrometers wide.The iPhone 4 Retina display features:
3.5 inch diagonal LED display with IPS technology
960 x 640 pixel resolution at 326 pixels per inch
800:1 contrast ratio
IPS technology stands for in-plane switching, which improves the quality of the image at more extreme viewing angles. The IPS screen will look better and have improved color reproduction when viewed from a side angle.