that’s enough for today.

by cloudier

Over the weekend, we saw the swirling rumors around the specs for the (presumably inevitable) iPad 2 start to come together. One of the most intriguing suggestions, which Engadget claim to have a reliable source for (and MacRumors some corroborating evidence to boot) is a higher resolution screen to match the iPhone 4’s Retina Display — specifically, doubling in both directions, changing from 1024×768 to 2048×1536.

This has prompted some discussion around exactly what Retina Display means, and whether this would count. The iPhone 4’s screen is a mammoth 326 pixels-per-inch (ppi), whereas this rumoured new iPad resolution is a somewhat lesser 264 ppi — quite a bit less. However, I believe it’s just as valid for Apple to call this a Retina Display as it was to call the iPhone 4 screen, and after the break I will explain why with some hopefully convincing mathematics.

Firstly though, it’s important to stress that these are only rumors and that 2048×1536 is an incredible number of pixels — 3,145,728 of them, in fact. That’s only 17% less than the 27″ iMac or 27″ Cinema Display, and it’s 52% more pixels than a 50″ 1080p television screen! This makes the screen expensive to make; it places greater strain on the graphics chipset to drive the screen, which makes that more expensive too; and it won’t do the battery life any favors either. All of this, to my mind, suggests this is one rumor that might come down to wishful thinking. As John Gruber said: “I’ll believe it when I see it“.

Apple could mitigate these problems by choosing some display size between the current one and the rumored twice-in-each-direction increase, but that brings fresh problems. The iPhone 4’s Retina Display increased resolution from 480×320 to 960×640 — so each single pixel on the old screen became a block of 2×2 pixels on the new screen. This means developers didn’t have to do anything to their apps to support this new screen; they would look exactly the same as they used too. Many devs did upgrade their apps to add higher-resolution graphics, of course, but the important thing was that everybody standing in line on launch day could bring every app they’d already bought over to the new phone unchanged. That’s the sort of seamless user experience we expect from Apple, after all.

If Apple used some intermediate resolution for the iPad 2, then all existing iPad apps would have to be scaled by some awkward factor by the hardware, and there’s no good-looking way to do that. If you try to take what used to be two pixels of display, and remap it to fill three pixels instead, then it’s a one-way trip to visual artifact city. The day one user experience for everyone upgrading from the mark 1 iPad would be that their existing apps look worse — which doesn’t make for happy users. So if it is going to increase, it seems likely it will indeed increase by a factor of two in both dimensions — hence the magic value of 2048×1536.

What makes a Retina Display?

The term “Retina Display” seems to be widely interpreted in the Mac blogging world that as meaning a display that has more than 300 pixels-per-inch, as that’s the limit the human eye can perceive. Hence the iPhone 4’s 326 ppi screen is therefore sufficiently pixel-packed that the naked eye can’t see the pixels, and a 2048×1536 iPad screen wouldn’t be a Retina Display because it only manages 260ppi. This, however, ignores the important factor of viewing distance.

The capability limit of the human eye depends on how close you hold things, and that’s not accounted for in the 300 ppi figure. The usual figure quoted in the literature for 20/20 vision is that the eye can tell the difference between two lines that are more then one arc minute apart — i.e., 1/60 of a degree. Consider two lines a millimeter apart. If you hold it right up to your eye, you’ll see two lines; move it ten feet away, and it’ll look like a single line instead. So if the question is “how small does a pixel need to be before I can’t see it any more,” then the answer has to depend on how far away from the screen you are.

As an aside, it’s also worth stressing that 20/20 vision means average, and is not some sort of gold standard for vision. It means when you’re standing 20 feet back from an eye chart, you can read the same amount of text as a normal person can. If you have 40/20 vision, it means you can be 40 feet back from that chart, and still read the same amount as a perfectly average person who is 20 feet back. Similarly, if Hans Moleman has 5/20 vision, he has to walk just five feet away before he can read the chart. All the calculations below are for people with average vision — eagle eyed users will always see more detail.


I think it’s fair to say that, for users with average eyesight using their iPad in fairly normal ways (i.e. in their lap, on a desk, or on their chest when lying down), the rumored new display could legitimately called a Retina Display despite having a lower pixel-per-inch figure than the iPhone 4.

Of course, there is a big footnote here — Retina Display is a marketing term. It doesn’t have a scientific definition and it’s not an ISO standard; it means whatever Apple’s marketing folk want it to mean, and they were free to call it a Retina Display anyway — but if you see any anti-Apple bashing for allegedly misusing the term, you can point ’em here and straighten ’em out.

Here’s my point: I do not think the hidden message vanishes when the movie goes Hollywood and happy. I believe the resolution of the darker movie is, in fact, still there, wrapped around the happy ending of the classic. Look again at the closing frames — shots of Jimmy Stewart staring at his friends. In most, he’s joyful. But in a few, he’s terrified. As I said, this is a terrifying movie. An hour earlier George was ready to kill himself. He has now returned from a death experience. He was among the unborn, had crossed over like Dante’s hero, had seen this world from beyond the veil. In those frames — “The Night Journey of George Bailey” — I don’t think he’s seeing the world that would exist had he never been born. I think he’s seeing the world as it does exist, in his time and also in our own.

George had been living in Pottersville all along. He just didn’t know it. Because he was seeing the world through his eyes — not as it was, but as he was: honest and fair. But on “The Night Journey,” George is nothing and nobody. When the angel took him out of his life, he took him out of his consciousness, out from behind his eyes. It was only then that he saw America. Bedford Falls was the fantasy. Pottersville is where we live.

I love this interpretation of the film – it made me go watch it.
When WikiLeaks in mid-2010 published documents detailing the brutality and corruption at the heart of the war in Afghanistan, the Chairman of the Joint Chiefs of Staff, Adm. Michael Mullen, held a Press Conference and said of WikiLeaks (and then re-affirmed it on his Twitter account) that they “might already have on their hands the blood of some young soldier or that of an Afghan family.”  This denunciation predictably caused the phrase “blood on their hands” to be attached to WikiLeaks and its founder, Julian Assange, in thousands of media accounts around the world.  But two weeks later, the Pentagon’s spokesman, when pressed, was forced to admit that there was no evidence whatsoever for that accusation:  “we have yet to see any harmcome to anyone in Afghanistan that we can directly tie to exposure in the WikiLeaks documents,” he admitted.  Several months later, after more flamboyant government condemnations of WikiLeaks’ release of thousands of Iraq War documents, McClatchy‘s Nancy Youssef — in an article headlined:  “Officials may be overstating the danger from WikiLeaks” — reported that “U.S. officials concede that they have no evidence to date” that the disclosures resulted in the deaths of anyone, and she detailed the great care WikiLeaks took in that Iraq War release to protect innocent people.