Very surprised to read this part from Gruber's blog. I guess it upscales apps to 2208 x 1242 and then downscales them to 1920 x 1080 on the fly. Kinda wonky...
Physically, it is a 1920 × 1080 display with 401 pixels-per-inch. Virtually, however, it appears to apps as a 2208 × 1242 display with 463 pixels-per-inch. Those latter numbers should sound familiar to regular readers. The iPhone Plus automatically scales the 2208 × 1242 interface to fit the 1920 × 1080 display. This on-the-fly downsampling sounds crazy it sounds like something that might be slow, and that might lead to fuzziness on screen with small text or fine lines. In practice, it just works. Text and fine lines appear sharper on the 6 Plus than on the regular 6 (or any other iPhone with a 326 PPI display, like the 5s). 401 pixels per inch is high enough that things still look great even if theyre not pixel-perfect. I was deeply skeptical of this on-the-fly downsampling when I heard about it, but having used it for a week, Im sold.
(When you take a screenshot on the iPhone 6 Plus, you get a 2208 × 1242 image you get a screenshot of what the app thinks it is displaying, not a screenshot of the actual pixels on screen. If you really do care about pixel-level precision, Im not sure how you can tell what is being rendered on screen other than to examine the actual iPhone display using an optical loupe.)
But why is Apple doing this? Itd be simpler, for sure, to just use an actual 2208 × 1242 display and to continue rendering truly pixel-perfect interfaces. Well, simpler conceptually. In practice, though, there would be trade-offs. More pixels would consume more energy, and higher density displays are harder to manufacture. There are diminishing returns to packing more and more pixels per inch and having used the iPhone 6 Plus for a week, I cant complain about a single aspect of this downsampling design. I can definitely tell the difference between the pixel density of the iPhone 6 and 6 Plus. Im not sure at all that Id be able to tell the difference between the actual 1920 × 1080 6 Plus and a hypothetical next-generation model with an actual 2208 × 1242 display.