The Plus, though, works differently. 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.)