Today, Apple announced the new iPad 3, which has a bunch of new features and improvements over the iPad2. One of the new features is a much higher resolution display: 2048 x 1536 pixels, which they advertise as a "retina" display: ad-speak for pixels so small your eye can’t see them. The display looks smooth and unpixellated.
But is that really the case? I did a little math and found this claim to be true, more or less. But there are some caveats, and they’re interesting.
[By the way: I've done the math here in imperial units, and not metric, because that's the standard the industry uses for pixels and such. Silly, but it's one of the last holdouts you'll see used this way.]
iBalling the numbers
First, you should really read my post Resolving the iPhone resolution, where I first dissected the "retina display" claim for when the iPhone 4 came out. My conclusion then was that yes, the iPhone 4 display has pixels so small you can’t see them under normal circumstances. But in that post I did a bit of math to prove it.
What I found was that if you hold a device about a foot away from your face and have normal vision, the pixels need to be smaller than 0.0035 inches in size for them to be unresolved; in other words, pixels at this size or smaller give you a "retina display". The iPhone 4 has pixels about 0.0031 inches in size, so it wins.
But what about the new iPad?
The new iPad is reported to be the same size as the iPad 2, with a display of 7.75 x 5.8 inches. But it does have smaller pixels than the old version! Dividing the size of the display by the number of pixels (2048 x 1536) we get a pixel size of 0.0038 inches (or 264 dots per inch, if you prefer).
Uh oh. That’s actually a bit bigger than what your eye can see! So is this truly a "retina display"?
Well, let’s not be too hasty to poo-poo this new tech. For one thing, the iPad display is only resolved if you hold it a foot or closer to your eyes. After a little testing, I found that I tend to hold my own iPad 2 about 15 – 17 inches from my face. From that distance (let’s call it 16 inches), pixels need to be smaller than 0.0047 inches to be unresolved (again, see my old post about how that works and where that number comes from), and the iPad 3′s pixels are certainly smaller than that!
If you do happen to have perfect eyes, under ideal circumstances you’ll probably be able to see the pixellation in the screen, but it won’t be that big a deal, I’d wager — and if you hold the iPad 3 about 18 inches from your face, the pixels are too small to see in any case. So, for the majority of people, the claim of a "retina display" is probably accurate.
I’ll note, though, that the iPad 3 pixels are larger than those for the iPhone 4. But that’s OK; I tend to hold the iPhone a little closer to my eyes than I do the iPad. In either case, I’m unlikely to see the pixels.
I imagine there will be a lot of writing about the display for the iPad 3, with some people loving it and others hating it — that’s inevitable when new tech comes out, especially when Apple is behind it (I’ll note my original resolution post was in response to what I thought was an unfair denigration of the iPhone 4′s display). Incidentally, Boing Boing reports the new iPad will have 40% more color saturation. A display with more colors can trick the eye into thinking the resolution is better, so this will also help the "retina display" claim.
And yes, duh, of course I want one! But I tend not to jump into new tech, and besides, I got the iPad 2 just a few months ago. I like it, and it’s fine for me; the new features are not anywhere near enough for me to want to spend the money to upgrade. Hopefully, my iPad 2 will last long enough that when the iPad 4 comes out, by then I’ll be ready.
Image credits: Apple; wikipedia. Note: I had incorrectly called this a "retinal display", so I have corrected the text. Thx to huggyb for pointing this out.
[Update: Some people in the comments are complaining I didn't use metric units in this article. I'll assume they're new to my blog; I usually do use metric. However, note the original quote by Steve Jobs is in Imperial units, not metric, so I used those for consistency. Also, the units don't matter, since I could have used pixels per hogshead if I felt like it. What matters is the way the numbers compare to each other, as long as the units are consistent.]
With much bruhaha, Steve Jobs and Apple revealed the new iPhone 4 yesterday. Among other features, Jobs said it has higher resolution than older models; the pixels are smaller, making the display look smoother. To characterize this, as quoted at Wired.com, he said,
It turns out there’s a magic number right around 300 pixels per inch, that when you hold something around to 10 to 12 inches away from your eyes, is the limit of the human retina to differentiate the pixels.
In other words, at 12 inches from the eye, Jobs claims, the pixels on the new iPhone are so small that they exceed your eye’s ability to detect them. Pictures at that resolution are smooth and continuous, and not pixellated.
However, a display expert has disputed this. Raymond Soneira of DisplayMate Industries, was quoted both in that Wired article and on PC Mag (and other sites as well) saying that the claims by Jobs are something of an exaggeration: "It is reasonably close to being a perfect display, but Steve pushed it a little too far".
This prompted the Wired article editors to give it the headline "iPhone 4’s ‘Retina’ Display Claims Are False Marketing". As it happens, I know a thing or two about resolution as well, having spent a few years calibrating a camera on board Hubble. Having looked this over, I disagree with the Wired headline strongly, and mildly disagree with Soneira. Here’s why.
First, let’s look at resolution*. I’ll note there is some math here, but it’s all just multiplying and dividing, and I give the answers in the end. So don’t fret, mathophobes! If you want the answers, just skip down to the conclusion at the bottom. I won’t mind. But you’ll miss all the fun math and science.