Sizing up the display on the iPhone 5

John Gruber has a pretty emphatic opinion on why Apple’s next phone *may* have a larger screen, but he doesn’t see the device being larger in itself.

This is why it won’t work.

Apple’s current displays are 3.5” on the diagonal that have a 960×640 resolution. When Apple introduced the iPhone4, they took great care to ensure that they didn’t mess around with two things:

1. Size: 3.5” was the size that Jony Ive wanted and that Steve Jobs blessed . And 3.5 inches it was. There is enough material floating around the internet on the possible reason for this.

2. Resolution: The original iPhone saw its first 3 avatars at a display resolution of 480×320. And by the time the iPhone 4 launched, there was a non-trivial number of applications built that were optimized for this screen.

This is a nuance that cannot be overstated. Unlike desktop operating systems with applications that can pretty much adapt to dozens of displays with resizable chrome, mobile apps are built to exploit every pixel. That’s why there are no-resizable chrome elements on a mobile app (ever see a maximize or minimize button?). And that’s why Apple had to make a display choice that didn’t fracture the ecosystem that they were beginning to see explode.

So enter 960×640— which effectively doubled the number of pixels in both x and y. This meant each pixel element on a legacy 480×320 screen would now be doubled along both axes- while keeping the aspect ratio the same at 3:2. The OS would do all the abstraction for you- and you the developer didn’t have to move an inch. That way a lazy developer could have his app intact without the OS and screen not messing with his layouts, assets and UI elements.

These 2 elements combined to give the famous retina display- that at 3.5” and a 960×640 resolution ended up in an astounding 326 pixels per inch on the diagonal.

Now let’s speculate a little- let’s assume that Apple is forced to go to a larger display due to the chipset, antenna and battery needs of LTE. Let’s also assume that Apple does not want its 600K+ apps to break. It’s only logical that they try and fill the front face with a proportionally larger display and keeping the bezels (the black border around the display) as minimal as possible.

The problem is that for every 3 pixels Apple adds vertically, they have to add 2 horizontally. There is simply no way that Apple will be able to stretch the display in only one dimension because, apps are going to get skewed/ stretched/ letterboxed in ways unimaginable.

This also means there is no way in which they will add any more pixels along the longer edge of the display.

Apple’s options:

So let’s assume that the display does grow larger to 4” , and lets also assume that Apple wants to keep its apps intact. The options are:

1. Keep the 960×640 count: This leads to 288 dpi— very competitive, but still a step down from what iPhone users are used to, and much lower than what Samsung is pulling off on their HD monsters.

2. Move to a different pixel count: Apple can either do 3x the original iPhone @ 1440×960 (433ppi) or an even more ridiculous “double retina” at 1920×1280 (577ppi). (Thank you DPI Calculator) Two problems here:

-Can vendors even do this given the rumors we are hearing around the poor yields for the 2K display for the iPad3?

-It’s a lot of pixels for even the rumored quad core A6 to crunch through without frying itself.

3. Adopt the iPad pixel mechanics on a smaller display:  That would mean 1024×768 @ 320 ppi, enough “retina” to remain competitive. But apps are broken again because of a different pixel count compared to the traditional iPhone model.

Extending this argument:

Take 1, 2 and 3 together and you see the point I am trying to make. Given Apple’s approach so far, they can only get a small increment in size over their base 3.5” if they want to maintain the “retina” aspect and keep apps reasonably compatible. But this may not be sufficient to visually appeal on a device whose XL size mandated by the overheads of LTE.

Another option is that they meddle with the pixel count, aspect ratio and pixel density to get the best combination of display size and crispness relative to device footprint. But messing with either of these three may mean an impact for developers- apps have to be reworked on different levels. Too risky.

A third option is to try and mess with AMOLED and the PenTile system of counting pixels. This way they can keep the 960×540 count on a larger size and instead tout the benefits of AMOLED whilst conveniently relegating the pixel arms race to the back burner. Would they do it? (Update: Probably not with all this other stuff happening!)

But given Apple’s track record, they might just do a fourth completely different option and pull another rabbit out of their hat one more time.

Update: With some leaks coming in, John has taken another stab at scoping the display on the new iPhone. I tend to agree more with John’s line of reasoning though I can see some developers of pixel perfect apps (games, print media etc.) throwing up their arms in frustration.  Still better than this option though.

Oh, and yes, it looks like the next iPhone most certainly does not have an AMOLED display.

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