The iPhone 4's Retina Display rightly gets praise for its high pixel density. Since its release, many iPad owners have longed for Apple to bump up the display resolution from 1024 x 768 in order to provide a similar viewing experience on Apple's tablet. When viewing an iPad's display next to an iPhone 4's Retina Display, the iPad appears excessively pixelated, particularly in text-heavy apps like iBooks.
Pixel density aside, recent analysis by Dr. Raymond M. Soneira of DisplayMate Technologies shows that the iPad 2's display stacks up well against the iPhone 4 in most other measures. According to Dr. Soneira, "the display on the iPad 2 delivers almost identical performance to the impressive iPhone 4 Retina Display," for the values he measured. Dr. Soneira compares the iPhone 3GS, iPhone 4 and iPad 2, and he analyzes values such as brightness, contrast ratio, black levels, and viewing angles to give us an idea of how Apple's newest device stacks up. In most respects, the iPad 2's display does indeed perform similarly to the iPhone 4, and both devices have measurably superior display quality compared to the iPhone 3GS.
Although the iPad 2 display's 132 ppi doesn't compare favorably to the iPhone 4's 326 ppi, Dr. Soneira calls the pixel density on the Retina Display "overkill" anyway. He believes some of the iPad 2 display's shortcomings could be addressed in software; Dr. Soneira says "anti-aliasing on the iPad 2 is far from state-of-the-art and degrades the perceived sharpness of text and graphics." Indeed, comparing the anti-aliasing on an iPad display versus a notebook display with a similar pixel density shows the iPad suffers from greater pixelation.
Some iOS developers, such as Firemint and Chair Entertainment, have already taken advantage of the iPad 2's better graphical performance, and using techniques similar to the ones Dr. Soneira advocates, these developers have delivered superior-quality graphics in their apps even though the display resolution remains the same. With its limited RAM and less powerful A4 processor, it's possible the original iPad lacked the processing power necessary to support anti-aliasing similar to that accomplished on Mac displays, but the iPad 2 should be able to do so.
Perhaps improved anti-aliasing for the iPad 2 is something we should add to our wish list for iOS 5.