It's not a resolution per se, it's the resolution at which you can't tell the difference between pixels when viewing the screen from a distance you would typically use the device. So it'll be different for a handheld, a tablet, and a notebook.
- Victor Ganata
Sure but need the tech spec for each "retina display" device so to compare the screens. For example, what is the resolution on the new iPad and the iPhone 4S?
- Kol Tregaskes