If Apple is transitioning to larger iPhone screen sizes, they will need to increase the screen’s resolution to retain Retina pixel density. For Apple to consider an iPhone screen to be Retina, the screen must have a pixel density above 300 PPI. Current 4″ iPhones have a resolution of 640 x 1136. This gives the 4-inch display a pixel density of about 326 PPI. If this resolution expanded to the predicted 4.7″ and 5.5″ sizes, their respective pixel densities would be 277 PPI and 237 PPI. Both are clearly below the Retina threshold.
When Apple went Retina with the iPhone 4, they used a new “2x” resolution. This meant that they doubled the resolution dimensions from 320 x 480 to 640 x 960. 2x screens display 2 pixels in each dimension for each 1x pixel. Since apps are written referencing the 1x resolution, this strategy kept all content to scale, and made the transition fairly easy for developers. When the iPhone 5 increased the screen size from 3.5″ to 4″, Apple brought the screen to a 16:9 ratio by adding pixels to the height, while leaving the width alone. Because the screen only increased in height, they created space for more content. Again, this kept all existing content to scale.
Prior rumors have suggested that the new iPhone 6 models will sport a 960 x 1704 resolution, which would be considered a 3x resolution. This would mean that 3 pixels in each dimension would represent each 1x pixel. If Apple was keeping the screen size at 4 inches, this would keep all content to scale. However, the next screen transition will be different than previous ones. Apple won’t be packing more pixels into the same space, and they won’t be adding pixels in one screen dimension. iPhone 6 screens will be scaled up, and larger overall. If Apple uses the 3x strategy, content will be scaled up along with the screen. This will not take advantage of additional screen space.
If Apple wants to keep content roughly the same size while increasing screen real estate, they can’t just bump the resolution up to 3x. Compared to the 4″ screen, a 4.7″ screen will increase the width and height by about 18%. A 5.5″ screen will increase the dimensions by about 38%. These increases would also be reflected in the size of screen content if Apple bumped up to 3x. In order to fully take advantage of screen space, Apple will have to increase the pixel dimensions by some amount between 18% and 38%.
9to5Mac has been digging through some iOS 8 files, and they have found a plist for a 1x resolution of 414 x 736. That makes the 2x resolution (the resolution of the display) 828 x 1472. These dimensions are a 29% increase, and are Retina for both 4.7″ (359 PPI) and 5.5″ (307 PPI) display sizes. The 29% increase is a very happy medium between the 18% and 38% increases in screen size. This would make content scale very nicely between the two screen sizes, much like the iPad Air and iPad mini with Retina display.
Feld & Volk has leaked several iPhone 6 parts so far. After seeing the resolution in the iOS 8 files, they decided to take their leaked panel under the microscope (literally) to verify the resolution. Strangely, they claim that their 4.7″ panel is the 3x resolution of 960 x 1704. MacRumors calculated the pixel density in Feld & Volk’s photo, and found that it’s actually closer to what the 828 x 1472 display would have. This is now raising speculation that Apple could implement both resolutions, one for each screen size. That seems fairly unlikely given the iOS 8 file, and Apple’s record of keeping their number of resolutions to a minimum.
Although a 3x bump would be faster and easier for developers, it could be harder for developers to make their apps look good on larger screen sizes. Apple has consistently criticized Android tablets for using scaled up phone apps, so they probably have no interest in simply scaling everything up for their future line of iPhones. The 3x bump would also add excessive pixels (compared to Retina standards) that would require more power.
It would make sense for Apple to use one resolution between their two new iPhones. Logic seems to point in favor of the 828 x 1472 resolution. Apple is developing for this screen resolution, it’s Retina at 4.7″ and 5.5″ screen sizes, and it adds an appropriate amount of screen real estate. Of course, this is all rumor and speculation until the official announcement. We’ll be sure to keep you up to date on the latest iPhone 6 news. Do you think Apple will use both resolutions, or just one? Which one do you think they’ll use? Let us know in the comments.