When Apple discusses retina resolutions, it's usually accompanied by an equation that factors in not just the physical size of the screen, but also the distance from which that screen is viewed. Because we naturally view larger screens from farther distances, screens don't need to maintain the same pixels-per-inch (ppi) spec as they grow to qualify for the 'retina' label.
- iPhone 4 (typically viewed from a 11" distance) has 326 ppi
- New iPad (typically viewed from 13") has 264 ppi
- New Macbook Pro (typically viewed from 15.5") has 220 ppi
Richard Gaywood wrote a great article for TUAW explaining the mathematics behind this. This got me curious about what resolutions would be required if Apple decided to extend retina displays across their entire product line. This chart is what resulted.
We thought it was interesting to note that HDTV isn't that far from a retina display at the current resolutions of 1920x1080 — and depending on how far you sit from the screen, it could very well be a retina display already for you. So don't get pixel count envy until you also factor in your likely viewing distance.
(Images: Chris Perez)