iRetina Display

It’s been three whole days since I started this blog and I have only just got around to raging on Apple products. Since this is my first mentioning of it, let me preface this with a little background. I suffer from an uncontrollable hatred of them. I just find that if when a piece of technology somehow emanates a field of utter smugness for several metres, it is very deserving of my ire. I also own an iPhone. It and I have a love/hate relationship. I mistreat it just because it is an Apple device, and yet I have it with me all the time because compared to all but the latest Android and Windows Mobile 7 phones, it’s by far the best, and most balanced portable internet gateway and gaming platform. It’s also a totally rubbish phone, but I suppose you can’t have everything. I even also have a Macbook Pro which is required for work, but I have naturally installed Windows 7 on it as I don’t wear a turtleneck.

I barely go a day without raging at an Apple product (probably because I have to actually use them every day) but given the recent news about the iPhone 4, I felt it was a good juncture to weigh in on something that has been irritating me since its release. I am speaking, of course, about:

The “Retina Display”

Apple’s marketing department has taken a leaf out of the pages of history, apparently assuming that if you tell a lie enough times, nobody is going to question it. Especially if you dress it up with a liberal dose of insufferable pretentiousness. But this, this is somehow special because it has possibly the worst case of wanky name syndrome that Apple have produced. During the same talk where Steve Jobs was telling the world how the iPhone antenna was utterly revolutionary (I suppose that saying it was “flawed and generally a bit rubbish” would have been a bad PR move – although I’m sure that the Mac fanboy hive mind would somehow spin it as being artsy and cool vs the suited, stuffy phones with functional reception), he also told his cult followers that the iPhone’s display, at 326dpi, was somehow beyond the “resolution” of the human retina, something which he quoted as 300dpi. I’ve been following a few news posts about this, because I want Apple to be totally wrong, but I think it’s time for me to weigh in with something more than mere trolling.

First, if he was talking about resolution in the non-computer-screen sense, i.e., the ability to resolve independent bits of information, Apple has a bit of a problem. People with normal visual acuity, or 20/20 vision, have the ability to resolve line pairs given a spacing of above 1 arc-minute, or 1/60th of a degree (for human vision, despite what Apple attempts to tell us, is measured in angular acuity, not dots per inch). If you do the maths, you end up at this becoming a planar resolution of about 300 pairs per inch at about a distance of a foot. Note that I didn’t say pixels, I said “pairs”. Human vision is a funny old thing and doesn’t actually work anything like a digital camera. Between your cone cells that perceive colour, you have tens more rod cells in the same central region, able to sense, with great accuracy, differences in luminance. In addition, you cells work in a very squishy, biological way, stimulating adjacent cells and causing localized feedback, which is why certain patterns, such as high contrast pairs of lines, are difficult to resolve, but high contrast step gradients are not. In short, for it to be completely unresolvable, each arcminute would need to have three pixels at a distance of 1 foot, or three times the dot pitch of the iPhone 4. This effect can also be seen with something called “Vernier Acuity”, where people with normal vision are able to align two line segments to a resolution of 0.13 arcminutes – our reconstruction of the world allows us to perceive data from our retina that is apparently beyond our physical ability to.

Next, if we’re talking about resolution in the same sense as a screen or TV, basically it’s just marketing nonsense. Bring an Phone up to your eye and you will be able to see the pixels. Humans have about 5 million cone cells arranged within some 100 million rod cells. We have a visual field (per eye) of about 160 degrees horizontal and 135 degrees vertical, with a central region of 60 degrees horizontally seen by both eyes. About the central 30 percent of our visual field sees colour, and our eyes dart about impercebtibly to fill in all the gaps. Using these numbers to come up with an aspect ratio of about 1.18:1, our cone cells have a computer-screen resolution of 2248×2058 pixels, but it doesn’t really work like that. Using the initial numbers above, dividing the visual field by the resolution, we end up with some preposterous size of around 300 megapixels. Theoretically such a display should be pretty much impossible to resolve if it covers our entire visual field, even if we have it right up against our face, but I suppose we’ll have to wait for that.

So either way you slice it, it doesn’t work. The iPhone 4 has a lovely S-IPS display with good contrast and it is very crisp, but every time I look at one I feel the urge to microwave it. I can’t help but wonder why Apple feels they have to pull this kind of nonsense all the time. I mean, when laser printers became commonplace and people could easily print at 600dpi, I don’t remember anyone trying to sell me “Retina Paper” to go with my magical new printer.