The first generation has a somewhat disappointing 1024x768 screen resolution display, this disappointment be even more evident when the iPhone 4 doubled the previous iPhone screen resolution. Previous discussion of the potential for a retina iPad display have lead many to believe this wasn't possible.
It appears that @StroughtonSmith has uncovered that the iPad 2 will be doubling the pixels based on icons and the wood tile background png files in iBooks version 1.1. Here are the icons below...
This information leads us to believe that the iPad 2 will have a resolution of 2048 by 1536. Essentially, this example was used to show that since the iPad is held nearly twice as far from your eyes, it still may achieve "Retina" status with a slightly lower DPI than the iPhone 4.
The doubling of the display resolution works well for app developers as well with an option for a 2x display, but this new resolution will be much more enjoyable once developers take full advantage of the iPad 2 screen capabilities!
The definition of a retina display in terms of DPI is weighted dependent on the viewing distance...when I was at the Big 12 Championship game at the new stadium in Dallas, the screen their definitely looked to be "retina" from the distance I was viewing!
This screen resolution is 2176 by 4864 with a width of 50' 4" and a height of 28'-7", my viewing distance was probably close to 150 feet.
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