# Eyeballing the iPad 3 retina display

By Phil Plait | March 7, 2012 2:06 pm

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.

Ah, iSee

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.

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1. Erik N

Don’t they call it a “retina” display, not “retinal”? “Retinal” display sounds like the display is embedded in your eyeball, which would probably be cooler than what it really means.

2. Dean

How does that compare to the iPad2? How far does it have to be to be ‘retinal’?

3. Elio

You forgot to mention that one foot is equal to 12 inches:
the rest of the world is not used to those silly measure units!!!

4. Sionyn

pixel size and distance basically
so your hdtv is a retina display since you sit at a distance were you cant see the pixels

5. Vanessa

I don’t suppose you can explain why it is nearly impossible for me to read an iphone when I have my polarized sunglasses on, can you?

I suppose I could just google it, but this seems like it’d be more technical than what yahoo answers can offer me.

6. Amanda

Love your blog! They do call it a “retina” display though not a “retinal” display don’t know if that matters at all in the discussion.

7. serenity

@Dean: The new one has twice the resolution on both axes – so 4 times the amount of pixels – 2048×1536 (3.145 MP) vs 1024×768 (0.786 MP).
Each “iPad 2 pixel” is now 4 pixels. So yeah, the difference is rather huge.

8. Peter Ellis

Dean: You’d have to hold an iPad 2 at ~2.5 feet (i.e. almost at arm’s length) for it to be “retina display”.

9. Darren

@5 Vanessa, the LCD screens work by exploiting polarization. The front of the display will be a linearly polarized screen.
http://en.wikipedia.org/wiki/LCD

Your sunglasses will usually be horizontally polarized. If your phone has a front screen that is vertically polarized, then it will be almost opaque. If you change the orientation, you should be able to see it pretty well.

Darren

10. I hear ya. My iPad 2 is only a few months old as well so I won’t be jumping on this one any time soon. I’ll upgrade when it can project a hologram of the Millennium Falcon into my lounge room.

11. CinC House won’t let me get one (yet). Although, maybe I can manage to hold out until the 4 comes out and get the first one there.

12. jesse

“Uh oh. [264 dpi is] actually a bit bigger than what your eye can see! So is this truly a “retina display’?”

Actually, all humans with correctly-functioning eyes can see almost everything bigger than pixels 0.0038 inches in size. What is the “biggest” thing you think I can see, anyway?

13. mannon

@Vanessa Darren is quite correct. Incidentally your polarized sunglasses are pretty much the same as the 3D glasses they give you at the cinema, only one lens is vertically polarized so that each eye receives a different image even though both are projected onto the screen. I noticed pretty much the same effect with my game boy screen except different colors were polarized in different directions. Thus rotating it make the screen change colors rather than simply going black. ;p

14. Nikita

Actually mannon, modern cinema 3D glasses are circularly-polarized: one lens polarised CW, the other CCW. This means that you can tilt your head whichever way you want, and the correct image will still go into the same eye. The older linearly-polarized glasses required you to keep your head nearly-perfectly vertical. Otherwise, if you tilted your head 45 degrees, both eyes would see both images. Tilt your head 90 degrees, and each eye would get the image intended for the other eye.

15. Tobi

It’s one thing to describe the pixel density in imperial measures.
But why did you use feet and inches to describe how far away you have to hold your iPad so it’s retina?

So wait, an foot is 12 inches, isn’t it (who came up with that idea?!?) and an inch is 2.54cm, right?
So a foot is about 30cm? Why not at least add this info in brackets?

16. Allen L

I just got inthe iPad 2 a few months ago as well. No interest in rushing out and buying the latest gadget. After all, it took me 2 years to get a smartphone (not an iPhone). I only bought. Smartphone when the umb phone died.

17. Allen L

I just got inthe iPad 2 a few months ago as well. No interest in rushing out and buying the latest gadget. After all, it took me 2 years to get a smartphone (not an iPhone). I only bought. Smartphone when the dumb phone died.

18. BJN

What the eye can see or not depends very much on proximity and other variables. 264 ppi is a really poor resolution for typography, it’s fine for bitmaps. For rendering clean vector graphics to print, you need 1200 dpi (in black and white the same thing as ppi) for decent clean curves, you need 2700 ppi to really render a curve with no aliasing visible at close proximity (to good eyes, but that’s always a given).

“Retina” is marketing speak, not science. A mechanical display array of gridded RGB pixels is not analogous to an organic photo receptor that has a mix of color and monochrome sensing cells that aren’t processed into a pixel grid by the brain.

As to the product, it’s the same inflexible device that doesn’t handle SD card reading well and without a separate adapter, has lousy web browsing limitations, and apps that have to play all on their own. I can accept that kind of dumb device stuff on a phone, not on a tablet. I’ll be replacing my iPad with something less limited and limiting.

19. lunchstealer

BJN,

I assume that is an aliasing issue, so you get, say a jagged line displayed to make a diagonal, and you can see the irregularity even if you can’t perceive the individual pixels making it up?

Also you’d probably be able to see Moire patterns in certain images, depending on the sampling method.

20. ian

“Well, let’s not be too hasty to poo-poo this new tech.”

You know, if there’s one thing I’ve learnt from being in the Army, it’s never ignore a pooh-pooh. I knew a Major, who got pooh-poohed, made the mistake of ignoring the pooh-pooh. He pooh-poohed it! Fatal error! ‘Cos it turned out all along that the soldier who pooh-poohed him had been pooh-poohing a lot of other officers who pooh-poohed their pooh-poohs. In the end, we had to disband the regiment. Morale totally destroyed… by pooh-pooh!

21. Tony Mach

Thanks for your display of this new fine gear, even if you prefer the old one. But do buy some carbon certificates from your PR salary, will ya?

22. HvP

ian, Baah!

Thank you, Darling.

23. Patrick Weigel

You forgot to mention that you had two eyes, not 10! That’s non-metric and so is bad and silly and out of touch with the rest of the world.

You forgot to mention that you had two arms, not 10! That’s non-metric and so is bad and silly and out of touch with the rest of the world.

24. I started in Apple, still have my II plus in the closet, but I left them about the same time Wozniak did. This tablet might bring me back if it’s as good as advertised.

25. Daniel J. Andrews

If you do happen to have perfect eyes, under ideal circumstances you’ll probably be able to see the pixellation in the screen,

Nit-pick. You don’t need perfect eyes to see them. If you’re near-sighted you’ll be able to see the pixels if you take off your corrective lenses. Actually, you’ll be able to see close objects in more detail than someone with perfect eyes. Depending on the degree of near-sightedness you can see detail that someone with a perfect eyes would need a magnifying lens to see. Rather a handy visual “defect” if your work involves looking at things close-up.

26. I am a video engineer.
This ‘retina display’ is pretty cool, but a little unnecessary. It will require a lot of GPU power for anything like games that render at that resolution.
Barco and other companies for years have made high end projection systems that can hit 2048×1536 for years, but we have never produced any content that uses that high of resolution in 4×3 format.
Is Apple trying to kill 16×9?
Who knows. We shall see.

PS
Dear APPLE, please stop using 1280×800 as a standard resolution. The rest of the world settled on 1280×720 for a standard. Please follow suit. It really messes things up when some jerkoff comes along with an improperly formatted video and it does not appear properly on globally (as in EARTH) standardized video screens.

27. Isobel_A

I found your last paragraph profoundly depressing. You hope your iPad 2 will last long enough for the iPad 4 to come out, about two years? It’s true but it’s awful. These things cost £500 (I don’t know what they cost in the US) and we hope they last two years! Hardly ecologically friendly, these chunks of disposable electronics.

28. Navneeth

First off, I apologise for suspecting in your inner nerd. When I saw the title, I thought it was about a post where you ogled over an iPad, but then as I read further, I realised the true nature of your post.

29. Rodrigo Valle

Phil, I know you and a lot of people love Apple and their technology, but for this article to be fair you should mention that a LOT of devices now days have over 300ppi displays, and some with mindbogling colors and contrast, like Super AMOLEDs (Samsung, Nokia).

30. Nigel Depledge

The BA said:

Well, let’s not be too hasty to poo-poo this new tech.

Well, it won’t last. The world has a small and finite supply of Indium, so this touchscreen tech is a passing fad.

31. Nigel Depledge

The BA said:

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

Well, maybe if they didn’t try to take control of the device away from the user who bought it at an extortionate rate, they’d get a bit more sympathy.

After finding out some years ago that you have to send your iPod back to Apple to have a worn-out battery replaced, I’m just not interested in anything they sell.

32. Nigel Depledge

Erik N (1) said:

Don’t they call it a “retina” display, not “retinal”? “Retinal” display sounds like the display is embedded in your eyeball, which would probably be cooler than what it really means.

Heh.

Interestingly, “retinal” is the oxidised (aldehyde) form of retinol (vitamin A) that serves as the first light sensor in the rod cells of the retina.

Retinal is a polyunsaturated aldehyde that exists in two main forms – all-trans or 11-cis (cis and trans refer to the geometry of its carbon-carbon double-bonds). Absorption of a photon causes a change from one form to the other (although I cannot recall which way round it goes).

33. Nigel Depledge

Vanessa (5) said:

I don’t suppose you can explain why it is nearly impossible for me to read an iphone when I have my polarized sunglasses on, can you?

I assume you mean polaroid sunglasses, right?

You might struggle to read any LCD display through polaroid material because the display itself relies on a nematic liquid crystal that rotates the polarisation of plane-polarised light. In the original LCD displays, the layer of liquid crystal sits between two layers of polaroid material arranged to poalrise right-angles to one another, with illumination from behind the display. Normally, the display is dark; where a voltage is applied, the liquid crystal rotates the polarised light and allows it to pass through the second layer of polaroid.

More modern displays have diferent arrangements of polaroid and light source to make them more energy-efficient, but the fundamental idea is the same – that the liquid crystal layer determines which parts of the display are bright and which parts are dark, according to the rotation or otherwise of plane-polarised light.

If you rotate your iphone through 90° while looking at it through your polaroid sunglasses, you will see parts of the display brighten and darken according to what is displayed on the screen.

34. Nigel Depledge

Tobi (15) said:

So a foot is about 30cm?

More precisely, it’s 30.48 cm.

35. Beaky

Phil says “I’ve done the measurements in Imperial units, not metric. This (display measurements) is one of the last places you’ll see that still use Imperial units.”

One of the interesting things about the metric system is the number of different things
in it that are NOT metric. Considering just inches:
1. Display diagonal measurements and pixel sizes are usually given in inches
(but not always; some TV screens are metric-sized.)
2. The tripod socket on every camera I’ve seen is 1/4″ x 20 tpi, as are the bolts on every
tripod.
3. The square drive head on every socket wrench, and socket, are 1/4, 3/8, 1/2 or 3/4
inches.
4. Dimensional lumber in the UK, Canada, New Zealand and Australia is sized in inches,
as in “4×2″, “6×2″, 12×1″. (rough-cut, finished lumber is smaller but uses the same
measurement to keep everyone doubly confused.)
5. Bicycle wheel diameters (except for one metric size, 700 mm)

6. Speeds and distances at sea and in the air (nautical miles, = 72,912.7872 inches
or 1.852 km) (a degree of latitude (and longitude at the equator) = 60 nm, which
may account for its continued use.)
7. Typewriter keyboard spacing (3/4″ between key centers, 3/8 and 3/16″ row offsets)

There are many more examples. Inches are still everywhere!

36. Renee Marie Jones

Pixel size is not the only thing that matters. I suspect that the display is still no more than 8-bit per color and, although the eye cannot distinguish separate colors at that level, it *can* detect the discontinuity in the derivative in a color gradient, giving rise to false contours.

I am also wondering about interference effects that may be visible when the pixel size is approximately matched to the retinal sensor size.

If Apple is claiming that making pixels this size makes them “invisible” then they are either ignorant or being very misleading. However, I am sure that their lawyers have determined that such misleading statements are not actionable.

37. Wow, Phil, that was really…. uh, interesting… except that you forgot to put the little “Sponsored Post” banner across the top of that post. You also forgot to mention whether or not the worker who built your iPad has committed suicide yet.

Oh, and please, no more shopworn lowercase-initialed iPuns. Please, Phil, iBeg of you.

38. llewelly

“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.”

Every time an industry standard digital display is put on a Mars probe, the risk of it crashing doubles.

39. DennyMo

Nigel Depledge Says:
“I assume you mean polaroid sunglasses, right?”

Nigel, I’m surprised to see you make such mistake. Polaroid is a company that specializes in polarized materials. They may make (or may have made) sunglasses, but that doesn’t mean all polarized sunglasses are Polaroid…

40. “Imperial units”, forsooth? Why? You’re not a Canadian, and you’re certainly not a Briton, Australian, or New Zealander—and Lord knows you’re not a Jamaican. As I recall, you live and work in the United States, a country that had seceded from the British Empire fifty years before Imperial Units were ever defined.

Perhaps you meant to say “US units”?

41. Brian Too

@31. Nigel Depledge,

Well then, everyone line up and get one while you can! I weep for the soon to be extinct Indium!

http://simpsons.wikia.com/wiki/Ribwich

42. Pedant Monkey

It bugs me that Apple call it the retina display when the resolving the pixel resolution is nothing to do with your retina…

43. Nigel Depledge

Beaky (36) said:

One of the interesting things about the metric system is the number of different things
in it that are NOT metric.

This depends entirely on what you mean by “the metric system”.

If you refer to the SI, then it does not recognise the inch except as 25.4 mm.

If you refer to common usage in coutries that have largely adopted metric measurements, then there is no “system”, as it differs from country to country.

Considering just inches:
1. Display diagonal measurements and pixel sizes are usually given in inches
(but not always; some TV screens are metric-sized.)
2. The tripod socket on every camera I’ve seen is 1/4″ x 20 tpi, as are the bolts on every
tripod.
3. The square drive head on every socket wrench, and socket, are 1/4, 3/8, 1/2 or 3/4
inches.

For some of these things, backwards compatability has been important. Either that, or 9.6 mm is so close to 3/8″ (for instance) as to make no odds.

4. Dimensional lumber in the UK, Canada, New Zealand and Australia is sized in inches,
as in “4×2″, “6×2″, 12×1″. (rough-cut, finished lumber is smaller but uses the same
measurement to keep everyone doubly confused.)

But a piece of 4×2 (for example) will never be 4 inches by 2 inches. It’s always a bit smaller. So the term “4×2″ is just a relic. You might as easily call it 96×48 mm. You might even be a bit more accurate.

5. Bicycle wheel diameters (except for one metric size, 700 mm)

No, because 700 mm is the standard diameter for a proper bicycle wheel. It’s only toy bikes, like stunt bikes and mountain bikes, that use inches.

6. Speeds and distances at sea and in the air (nautical miles, = 72,912.7872 inches
or 1.852 km) (a degree of latitude (and longitude at the equator) = 60 nm, which
may account for its continued use.)

Eh? I think a degree is bigger than 60 nanometres.

Oh, you meant nautical miles. Right, got it.

7. Typewriter keyboard spacing (3/4″ between key centers, 3/8 and 3/16″ row offsets)

There are many more examples. Inches are still everywhere!

And this last one is another example where the metric conversion is so close to the Imperial original that they have probably changed it without anyone noticing.

While we’re at it, I’m surprised you don’t mention car tyres, which use the craziest system to specify their size. They use mm, % and inches. Thus, 225/40 R18 tyres are 225 mm wide, have a profile of 40% and fit a rim diameter of 18 inches.

But none of these units is part of any metric “system”. They survive through common usage.

44. Nigel Depledge

Denny Mo (40) said:

Nigel, I’m surprised to see you make such mistake. Polaroid is a company that specializes in polarized materials. They may make (or may have made) sunglasses, but that doesn’t mean all polarized sunglasses are Polaroid…

There is no such thing as a “polarized [sic]” material. Waves – particularly of light – are polarised, or not. The substance that admits only one orientation of plane-polarised light is described as polaroid. The fact that some company somewhere uses the same word with an initial capital as a trading name does not change the meaning of the original adjective.

The term you use – polarized – implies that the material is the recipient of the action of polarising, and this is not the case. A polaroid material permits the transmission of only one orientation of plane-polarised light.

I have a filter for my camera that is made of polaroid material. It is a circular polarising filter (not because it admits only circularly-polarised light, but because you can rotate it).

45. Bill

“Tobi Says:
March 7th, 2012 at 4:23 pm

So wait, an foot is 12 inches, isn’t it (who came up with that idea?!?) and an inch is 2.54cm, right?
So a foot is about 30cm? Why not at least add this info in brackets?”

I think the Babylonians came up with using units based on fractions of 60. 60 is evenly divisible by:
60, 30, 20, 15, 12, 10, 6, 5, 4, 3, 2, and 1. 100 is only divisible by 100, 50, 25, 20, 10, 5, 4, 2, 1 . 60 has more whole fractions which made it easier to divide the loot before calculators.

46. Actually, it’s the other way around: an inch is 1/12 of a foot; etymologically speaking, “inch” /means/ “one-twelfth”. (So does “ounce”; that’s why there are twelve Troy ounces in a Troy pound and twelve Apothecaries’ ounces in an Apothecaries’ pound. The reason that there are sixteen Avoirdupois ounces in an Avoirdupois pound is that it simplifies arithmetic for mathematically illiterate peasants.)

I think most English speakers expect those who know English as a second language to have at least a nodding familiarity with the pre-Metric systems, if only from their own national histories. A foot is not all that different from a /pied/, for example, an inch from a /pouce/, or a pound from a /livre/.

47. RobT

@Beaky – The tripod head bolt size is a standard that has been around for at least 100 years. My tripod head fits my new digital camera as well as my 90 year old Brownie camera, plus every other camera in between that I own.

@ CTSORLANDO – Apple has a very bad habit of having non-standard resolutions in most of their equipment. Somehow they called the original Apple TV an HD device with a 1280×720 resolution. Most every 720p display has a resolution of 1366×768 or 1360×768. Plus their aversion to playing video other than MOV or MP4 is really annoying. I dislike dealing with companies who dictate what you want to use instead of actually listening to what their customers want.

Don’t forget everyone, buy Apple products to support the underdog – Apple is only worth half a trillion dollars.

48. Melf_Himself

Some thoughts on your resolution calcs.

1) “Average” acuity of 20/20 corresponds to 1.0 arc min resolution
2) “Best possible” acuity is 20/10, which is 0.5 arc min
3) Aliasing may give some impression of the pixel array even when it can’t be properly resolved.

49. Bryce Walden

I really like high-resolution screens. But what peeves me is the wholesale abandonment of invariant standards in graphics, word processing and text in general. Used to be, when you opened an 8.5 x11 inch document on a Mac, you could hold a ruler up to the screen and the document measurements would be smack-on 8.5 x 11. Twelve-point font would be 12 points (12/72 inch) tall. Now every time we get an “improved” higher-resolution display, say at 4-pixels for every 1 of the lower-resolution, pages shrink to 1/4 their previous size and fonts shrink by half (if I’ve figured right). And it keeps getting worse. To add insult to injury, even Apple apps don’t let the user choose display font size, for instance. But pixels do not equal points and a 12-point font should be 12/72 inch on any resolution display. I think this is an OS problem that should be handled there. It’s also a common web page problem. The fact no one at Apple seems to understand this shows how their standards have eroded. Resolution-independent graphics. I think it was part of the specifications for something called QuickDraw. Does anybody over at Apple know what that is?

50. @ Bryce:
I know what QuickDraw was, and that Apple doesn’t allow to change Font Size on their ever higher resolution screens is annoying. Now we have Mountain Lion. Adjustable Fonts? Fehlanzeige.
I recently sold my 27″ Display to a 24″ Cinema LED, it is just so much more easy to read due to larger Fonts. However, looking forward to the new iPad’s Retina Display. If you are used to the iPhone 4 retina display, the iPad1 or 2 just doesn’t look that sharp and precise anymore.

51. Ultimately Apple has given us a new model that won’t feel any faster, but will be far more visually appealing to use, and sets the stage for what I feel will be the real performance increase next year.

There will be nothing at the iPad 3 release date from the Android camp that will match this tablet, and until that happens, if you need a tablet, while I still have my reserves, this is undoubtedly the tablet to get until we hear answers from the Android camp.
That will likely be in the form of the ASUS Transformer Pad Infinity, but with an availability date still unknown, the iPad 3 will get to enjoy this leap to market for quite some time.

Angel recently posted 3 Things You Need to Know About the iPad 3

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