Apple's 5-inch iPhone challenge

There's been a lot of chatter – all of it rumor mongering, with nothing official coming out of Cupertino – that Apple has an iPhone in the developmental pipeline which features a 5-inch display. But could Apple, from a technical standpoint, hit the iPhone with an expanding ray and take the screen to 5-inches?

I believe it can.

When the iPhone first debuted in 2007, Apple chose to go with a 3.5-inch display. At the time when smartphones had physical keyboards and everything was crammed into a small display above that keyboard, a 3.5-inch display was huge. It felt more like a having a flat-screen TV in the palm of you hand.

But times have moved on, and there are smartphones out there with bigger displays than the one found on the iPhone. In an attempt to fend off competition Apple already increased the screen real-estate to 4-inch with the iPhone 5, but a jump to a 5-inch display would be quite an increase.

If Apple is going to go large, there are factors that have to be taken into consideration. These include:

Resolution

The original iPhone had a 480 by 320 pixel display, which doubled to 960 by 640 pixels with the iPhone 4, and increased to 1,136 by 640 pixels with the release of the iPhone 5.

This resolution aspect ratio is important to maintain because it allowed apps to be backward compatible without any weird scaling issues.

The question is, could Apple double the resolution once again to 2,272 by 1,280? This might sound like quite a jump from the current, but given that there are plenty of smartphones on the market with 4.7-inch or 5.0-inch displays with screen resolutions of 1,920 by 1,080, this doubling isn't a fantasy by any stretch of the imagination.

I would assume that a 5-inch iPhone would maintain the 16 by 9 aspect ratio of the current crop of iPhones.

Pixel density

Apple is pretty proud of the fact that its devices – not just the iPhone, but the iPad and some MacBooks – sport a pixel density classed as "Retina display" (where the individual pixels are small enough to not be discernable to the human eye). When the iPhone 4 launched with "Retina display" it was a new thing, now

The iPhone 5, iPhone 5S, and iPhone 5C all have a pixel density of 326 pixels per inch. Increasing the screen size while keeping the resolution the same would mean that the pixel size would increase. The best way to offset this would be to double the screen resolution to 2,272 by 1,280. There are plenty of devices on the market with 1,920 x 1,080 displays that have high pixel densities, so Apple could pull this off with ease.

Battery life

Big screens consume more battery power. However, a larger display means a larger handset, which in turn means more space for a bigger battery.

Apple has kept the battery life of the iPhone at 10 hours, and I could see this being maintained for a 5-inch iPhone without any difficulty on Apple's behalf using current battery technology.

Ergonomics

One of the great things about the current iPhone is that a 4-inch screen makes the device suitable for one-handed use. Increasing the screen size beyond this would certainly make one-handed use challenging for people with small or average-sized hands.

This presents Apple with a problem. But it isn't one without possible solutions:

• Scale down the bottom bezel so the iPhone fits into the hand better.
• Develop gestures to allow users to navigate the large screen single handed
• Give up on single-handed use

The bottom line

Bottom line, I think that of all the challenges facing Apple, the ergonomic challenge will be the toughest for Apple to surmount, not the hardware challenges.

As to whether we'll see a 5-inch iPhone, I don't know. The iPhone continues to sell well and there doesn't seem much of a need for Apple to either go chasing after the crowd, or endorse handsets with a screen larger than 4-inches.

That said, Apple might be ready to give the handset another revamp, in which case going for a larger screen differentiates it from earlier models, which in of itself would be a selling point.