When Apple introduced the first iPad with Retina Display in March of last year, it didn't come without a cost. The third-gen iPad was the first Apple product to actually get fatter than its predecessor. Compared to the iPad 2, at 1.44 pounds, the iPad with Retina Display was about 50 grams heavier and oh-so-slightly thicker around the middle.
For a company that has always emphasized its ability to make each successive generation of its products lighter and thinner, the iPad with Retina Display was a real porker. The culprit? The Retina Display, and the 40% larger battery Apple needed to build into the iPad to power it.
First announced with the iPhone 4, Apple's Retina Displays are screens with pixels so small that they can not be individually seen by the human eye (when held at an average viewing distance). For the iPad, a Retina Display is made up of 2048 x 1536 ultra-tiny pixels, four times as many as a non-Retina iPad. Retina Displays are easier to read and more lifelike than regular displays. But those extra pixels really drain the battery.
A year and a half later, Apple seems to have solved the problem. Apple today unveiled the fifth-generation iPad, the iPad Air, and it has undergone a massive weight reduction compared to its predecessor: while maintaining the same battery life, the iPad Air now weighs just a pound. Likewise, the new iPad mini, while 0.3 millimeter thicker and about 20 grams heavier, is not significantly chunkier than its predecessor, despite needing enough battery to power a much more demanding 2048 x 1536 pixel display. How'd Apple do it?
Here's the one-two punch Apple used to solve the iPad's problems with battery life.
No matter how small, to power a mobile display, you need two things: enough graphics power to make the pixels dance, and enough battery to make them shine. Let's talk about the graphics first.
If you take a microscope to an iPad's screen, you're going to see a lot of pixels. In fact, there's over 3 million pixels packed into the Retina Display of an iPad Air or iPad mini, compared to around 786,000 in the iPad 2. Calculating what each and every one of those pixels is doing a few dozen times a minute requires a lot of graphics chutzpah.
When Apple decided to upgrade the iPad to a Retina Display last year, the company needed a chip that could crunch the numbers behind four times as many pixels as the iPad 2. There was only one problem. The A5 chip Apple had used in the iPad 2, and even the A6 chip the company debuted a few months later with the iPhone 5, couldn't handle that level of graphics performance natively. So Apple created a Frankenstein chip, called the A5X (and later succeeded in the fourth-generation iPad with the A6X), which essentially bolted more graphic cores onto their base level chips. This wasn't the most elegant solution. It made Apple's iPad chips much larger, and in the microprocessor world, the bigger a chip is, the more power it sucks up. The iPad's battery had to grow larger to compensate.
But with the iPad Air and Retina iPad mini, Apple has been able to finally ditch this Frankenstein approach. For the first time, the 64-bit A7 chip that Apple debuted with the iPhone 5s has powerful enough graphics in its default configuration to handle a 3-million-pixel-plus Retina Display. Apple was also able to shrink the down the process with which the A7 chip was made from 32 nanometers to just 28 nanometers—remember, the smaller a chip is, the less electricity it needs to run—meaning that, not only is the A7 chip powerful enough to drive an iPad's Retina Display, it's more power-efficient too.
But in the grand scheme of things, the chip inside an iPhone and iPad isn't actually the biggest drain on its battery. That honor goes to the display itself.
This is vastly simplified, but when you look at a computer screen, you're actually seeing three layers of components sandwiched together. From top to bottom, a screen is made up of a layer of pixels, a layer of transistors, and a backlight. The pixels determine the colors you see on the screen, the transistors connect the pixels together so your computer can control them, and the backlight shines light through the pixels so they can actually be seen.
It's the transistor layer that causes problems on screens with higher resolutions like the iPad with Retina Display. To vastly simplify matters, think of the transistor layer as a web of tiny wires that connect each pixel to one another. The more wires you have behind the pixels connecting them to one another, the more they obscure the light trying to shine through the pixels from the display's backlight. To compensate, the backlight—which is the most expensive element of a display when it comes to battery life—needs to shine even brighter (and therefore, use up more battery) to light those pixels up. The more pixels you have, the worse the problem gets.
For years, Sharp has been teasing a solution to the problem. Called IGZO, Sharp's LCD displays help solve the transistor problem by allowing more light from a display's backlight to shine through the pixels of the screen. Apple has been tipped for ages to make use of IGZO in its products, but up until now, it never has. During today's iPad event, Apple quietly made mention in their presentation unveiling the new iPad Air and Retina iPad mini that both devices used "improved backside illumination."
I'm just speculating here—it's not in Apple's nature to confirm it, so we'll have to wait until the iPad Air and new Retina iPad Mini are dissected by third parties in November for confirmation—but to me, that screams IGZO.
Designing a modern mobile device is a dance of a thousand trade-offs. With battery technology essentially stagnant, Apple can't just put a more advanced battery into a new iPhone or iPad to give it better battery life: the company can either make the device bigger or make the electricity gluttons inside a device that actually feed off the battery more frugal.
When Apple first upgraded the iPad with a Retina Display, the technology simply didn't exist to do anything but the former. But a year and a half later, thanks to the A7 processor and Sharp IGZO technology (or something like it), technology has finally caught up. These new iPads boast Retina Displays without the design trade-offs: they both weigh a pound or less, are light enough to hold with one hand, and unlike the last two Retina iPads, they have batteries small enough (while maintaining the same battery life) that they will no longer require as much as 10 hours to fully charge.
In a very real way, the iPad Air and iPad mini with Retina Display that Apple announced today are the iPads that Apple has wanted to release all along. These are the iPads we—and Apple!—deserve.