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The science of Retina displays

Posted on 5 Oct 2012 at 15:41

The Retina display: marketing genius or the future of laptops? David Bayon looks at how it works, what it means for developers, and whether to expect one on your next laptop

The march began in 2010 with the iPhone 4, gathered pace in 2012 with the third-generation iPad, and reached its dramatic peak last month with the launch of a new breed of MacBook Pro. As Apple adds its stunning Retina displays to ever-larger devices, resolutions climb higher, and the sharpness continues to appeal to an audience long fed on scraps by manufacturers.

How we’ve ended up in such a situation is a question many have been asking for some time. Have higher-resolution laptop displays been an insurmountable manufacturing issue, or is it the software that’s held us back? Could these sharper screens have been here years ago if manufacturers had only invested as they are – or, at least, Apple is – seemingly doing now?

In this feature, we look at how the field of display technology is taking leaps forward, largely – but not exclusively – driven by a single company. You’ll learn how Apple has managed to deliver panels at higher resolutions than its competition, how operating systems are making it all work, and whether the future is one of Retina-quality displays on every device.

MacBook Pro Retina

The numbers behind Retina

The MacBook Pro’s Retina display looks almost paper-like, and that’s down to two key design factors. First, it’s glossy, but without the usual feel of looking at a reflective pane of glass. This is because it’s constructed in a different way to standard LCD panels. As the teardown experts at iFixit explain: “Rather than sandwich an LCD panel between a back case and a front glass, Apple used the aluminium case itself as the frame for the LCD panel and used the LCD as the front glass. The entire display assembly is an LCD panel.” That’s why the panel is so thin, allowing Apple to trim down the MacBook Pro.

In most laptop displays, that would be the most interesting fact, but few could argue that’s the chief selling point of the MacBook Pro: the more important factor is pixel density. If you know the resolution and size of a screen, you can calculate the number of pixels per inch (ppi) it has, where a higher density makes each pixel finer and the overall image sharper.

In Apple’s own words, on a Retina display the “pixel density is so high your eyes can’t discern individual pixels”. If that statement sounds vague, that’s because it isn’t as simple as having a golden number to aim for. As screens become larger, so too does the distance from which they tend to be viewed; to have the same perceived sharpness, a smartphone in the hand must have a higher pixel density than a laptop on a desk.

Pixel density viewing angles

During Apple’s 2010 unveiling of the first Retina display on the iPhone 4, Steve Jobs announced a loose figure for smartphones. “There’s a magic number right around 300ppi,” he said, “that when you hold something around 10 to 12in away from your eyes is the limit of the human retina to differentiate the pixels.” There was disagreement at the time about the claim, since it falls some way short of the resolve of perfect vision – but few people have perfect vision. Instead, 300ppi is safely beyond the 286ppi capability of 20/20 vision from that distance, so for most people Jobs was right: the individual pixels are indiscernible.

In fact, the iPhone 4 and 4S have a 326ppi display, the latest iPad is 264ppi and the new MacBook Pro is 220ppi, all of which – given the variations in viewing distance – meet Jobs’ apparent requirement of invisible pixels with 20/20 vision. By contrast, a 15.4in laptop display with today’s most common 1,366 x 768 resolution has a density of 102ppi; even at 1,920 x 1,080, it’s still only at 143ppi. It’s possible to buy a 13.3in laptop at that resolution to give a better 166ppi, but it’s a rare option offered by a select few manufacturers.

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User comments

Retina Numbers: An alternative view.

I believe that the optimal resolution of a screen should be determined by the resolution of the human eye at its minimum focal distance (around 20cm) independent of the size of the screen.

The argument that you sit further away from a larger screen is bogus and seems to be based on being able to read the entire screen without moving your head. But we naturally move our heads when viewing a screen - closer and further to zoom in and out, side to side to focus on different detail. The illusion of perfection depends on not seeing the pixels under any circumstances.

Strangely, we all accept the right answer when it comes to printers: a minimum of 300dpi regardless of the size of the paper.

By JohnAHind on 6 Oct 2012

Emperors new clothes?

Personally I am extremely sceptical of the need for screens beyond 1080p on laptops. Higher resolution displays may smooth out fonts very slightly, but I suspect the advantage is minimal. Try as I might I just can't see the benefit of the higher resolution on the iPad3. Everything looks just the same as on a normal screen.

That said I would never buy a laptop with a resolution of less than 1080p.

By tirons1 on 6 Oct 2012


I see your point John; the problem is the extra expense and computing power required to show 300dpi goes up rapidly as screen sizes increase, while providing limited real world benefit.

The approach detailed in the article provides a pragmatatic balance between cost and performance.

By SirRoderickSpode on 6 Oct 2012


It is not bogus at all! Sit 10" from your laptop and see the individual pixels. Sit 5ft away and you won't see the pixels. Sit across the room from a large full HD TV and you won't see pixels.

Oh and you obviously don't work in professional graphics. Very larger prints intended to be viewed at greater distances are set up at WAY LESS THAN 300ppi.

By cooloox on 6 Oct 2012


It is not bogus at all! Sit 10" from your laptop and see the individual pixels. Sit 5ft away and you won't see the pixels. Sit across the room from a large full HD TV and you won't see pixels.

Oh and you obviously don't work in professional graphics. Very larger prints intended to be viewed at greater distances are set up at WAY LESS THAN 300ppi.

By cooloox on 6 Oct 2012


It is not bogus at all! Sit 10" from your laptop and see the individual pixels. Sit 5ft away and you won't see the pixels. Sit across the room from a large full HD TV and you won't see pixels.

Oh and you obviously don't work in professional graphics. Very larger prints intended to be viewed at greater distances are set up at WAY LESS THAN 300ppi.

By cooloox on 6 Oct 2012


I agree - but we should be honest and admit we are just settling for something less than optimal until the technology catches up.

Even Apple plays the game of screen size and viewing distance to justify why "retina" is lower resolution on a MacBook than an iPhone. We accepted visible pixels on printouts until printer technology was able to deliver 300dpi economically. On flat screens, it is still a compromise and not one we should put up with much longer.

It does raise the question: why buy a larger screen if it has the same number of pixels as a smaller one (and so a lower resolution)? Just get the smaller one and sit closer!

And @tirons1: 1080p is *not* a resolution. On an iPad, 1080p is a resolution of approx 130dpi. On a 60" plasma, it is only about 22dpi. But the ergonomic argument is different for full-screen video display as against text, still images and multi-media composites.

By JohnAHind on 6 Oct 2012


You must have very long arms if you sit 5ft away from your laptop! And there is no need to post in triplicate - this is not the Civil Service!

Of course you can find exceptions where it is a need for viewing by multiple people from a greater distance. My argument applies to personal information displays only.

By JohnAHind on 6 Oct 2012


I read my phone at 30 - 40cm from my face, my laptop is around 70cm from my face and my dual 24" display on the desktop at work is over 1M away.

With the laptop and the desktop, I can't get much closer, unless I stand up and lean over the desk.

The 15.6" FullHD display is about right for the size, I'd prefer 1920x1200, but it is okay. At the normal viewing distance, I can't make out individual pixels, but I do get a decent number of lines of text in my web browser. Looking at a 1400x900 or 1366x768, I really miss the extra height my display gives.

For me, the pixel density is more than high enough, what is important is the amount of information I can read.

I also have serious problems with "blurry" images. My left eye is a little weak and looking at text that is "a bit fuzzy" makes it go haywire, trying to focus.

It is one of the reasons I dislike the OS X rendering technology, which insists on rendering the font "correctly", so that it matches printed text, but the problem is, it ends up being unsharp and has artifacts that cause my eye to constantly seek to focus correctly, which ends up with a tick in the left eye and headaches.

By big_D on 7 Oct 2012

Of course both propositions are true!

"Retina", or more accurately displays offering very high pixel densities are BOTH the future, and a marketing gimmick.

They are the 'future' because as ever Apple didn't "invent" this type of display, but has been quick to promote it as its own.

Innovative display manufacturers like Sharp, and Samsung were developing the technology long before "Retina" was even a gleam in Cupertino's eye.

With or without Apple; increasing pixel densities are going to become the norm, and not just on 'phones & laptops, but where the money is: in TVs.

3D has been a bit of a flop, but 4k TVs could well be The Next Big Thing. These will, by definition[sic], be packing in the pixels, just like "Retina". That (not Apple) is the reason and the spur for the development of pixel-dense displays.
Samsung and other TV makers will make vastly more cash from flogging 4k TVs than they will from selling a few million PC & 'phone displays to Apple et al.

So Apple's prominent marketing of "Retina" is indeed 'marketing genius'. It both enhances their reputation for "quality" and "innovation" simultaneously bumping-up even further the per-unit margins on already profitable gadgets.

Steve Jobs would have been proud.

By wittgenfrog on 8 Oct 2012

It's just marketing distraction

Please focus on functionality and productivity, as I can read pretty much most displays without trouble.

By nicomo on 8 Oct 2012

The retina display is a Great Leap Forward

As a graphic designer who bought the retina macbook pro, iPad3 and iPhone 4 straight away, i definitely think retina displays are better. As well as the sharper text, it is miles easier to work on big posters and museum displays etc. as there is less zooming in and out.

All we want now is for the Adobe CS6 apps to support it.

By Duncanbaines on 14 Oct 2012

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