The new iPhone features a brand new, 3.5-inch 960-by-640 resolution LCD screen called a Retina display that boasts four times as many pixels as the iPhone 3GS. Apple says the new screen uses pixels that are just 78 micrometers wide, which is why it was able to pack so many more pixels into the iPhone 4 display than the iPhone 3GS. The new screen also features 326 pixels per inch, which Apple says is far denser than the human eye can distinguish.
In real terms, this means that when you hold iPhone 4 at a "normal distance" from your face images and video should look smoother and sharper than on previous versions of the iPhone. So with iPhone 4, expect less image distortion whether you are looking at a Web page, photo, or video. Apple claims the iPhone 4 has the highest resolution screen ever built into a smartphone.
The new Retina display also features LED backlighting, and the in-plane switching (IPS) technology used on the iPad. IPS makes it possible to have a wider viewing angle than on similar LCD screens, according to Apple.