iPhone 4: Retina Display

Apple (s aapl) has a new display to go with all the snazzy new features of the iPhone 4. The metaphorically named “Retina Display” sports 4x the resolution (double the pixel density) to provide a noticeably crisper and more detailed image. This new screen has a pixel density of 326 pixels per inch, compared to the 160 ppi display of the current iPhone. At this pixel density, the display is competing with the crispness of laser printing. The name was chosen because around 300 ppi, the human eye starts to lose track of the individual pixels.

I suspect that the display will cause a stir when we are finally able to see them in person. My first impression of the iPhone 3 years ago was that despite the other amazing technology in the iPhone, the display was what made it work because input and output are combined. This new screen will enhance the feeling that you are interacting directly with the technology.

The Retina Display provides additional enhancements beyond the increase in resolution. This screen is based on IPS technology (in-plane switching), which is also used in the Apple LED Cinema Display and the iPad. The contrast ratio has been bumped to 800:1 (4x better than the current iPhone) which will allow the Retina Display to provide even better rendering of details (particularly in shadows and dark scenes) for both photos and videos. Based on the specs alone, it looks to be an excellent screen. On paper, it compares very well to the OLED screen of the Google Nexus One (about 250 ppi) which was universally lauded for sharp text rendering.

It is also interesting to note that John GruberĀ nailed the specs on the screen (along with other key details) back at the end of March. Gruber also posted a breakdown of the ppi density of other displays back in 2007 when the hi-res MacBook Pro was released. This list, where most Macs have displays with PPI between 100 and 133, really highlights the significant improvement that a 326 ppi display represents over the displays we are used to seeing at our computers.

From the demos today, the iPhone OS appears to handle the difference in resolution seamlessly by scaling up the elements and interpolating edges to keep them sharp. Jobs did note that developers can provide higher resolution artwork in their apps to take full advantage of the Retina Display. I expect that some work will be required for developers to make their apps look their best on this new display, but it appears that current apps will look great as-is. The situation here is a bit different than the sometimes fuzzy scaling up of iPhone apps to the larger screen of the iPad because the elements will occupy the same physical space on the screen and should still look sharp.

I further assume that any apps that use the built-in facilities to render text will automatically benefit from the sub-pixel trickery to make text look sharper. One of the first real world tests will be to check out iBooks for iPhone on this new Retina Display. iBooks look great on the iPad and can only look better on iPhone 4.

I feel a little sorry for those poor 8GB iPhone 3GS units that will be on display next to the iPhone 4 in Apple Stores around the world.