Taller, thinner, and a metal back
As expected, the new iPhone is 18 percent thinner (0.30 inch vs. 0.37 inch thick) than the iPhone 4S. Apple says it's the thinnest handset around, but that's a race that changes often. That means it's also 20 percent lighter for a total of 3.95 ounces. The Retina Display expands from 3.5 inches (its size since the original iPhone) to 4 inches. The total resolution remains the same, though, at 326 pixels per inch. The total pixel count is 1,136x640, and we now have a 16:9 aspect ratio.
To the user, that means a fifth row of icons on the home screen. That's pretty nice since it will let you cut down on the number of home screens. You'll also get a full five-day week view in the calendar, the calendar will show more events, and all iWork apps will take advantage of the bigger display. Third-party apps that haven't been updated will continue to work, but you'll see black borders on each side (so they won't be stretched or scaled). Apple also promises that wide-screen movies will look better, with 44 percent more color saturation than on the iPhone 4S.