How Does The Apple Retina Display Work? [MakeUseOf Explains]

eye   How Does The Apple Retina Display Work? [MakeUseOf Explains]These days, people are crazy about the Apple Retina Display. Supposedly, it does wonders! A completely non-pixelated screen? Who would have ever thought?! However, many questions loom the supposedly revolutionary technological advancement. Is it really non-pixelated? How exactly does it work?

Fortunately, I’m here to answer nearly all of the questions you have about how the LCD Retina Display itself works. It’s a pretty nice piece of Apple hardware, and in my opinion, it’s a great leap forward into our screen-filled world. From PPIs to PPDs, I’ll tell you everything that you need to know that makes the Retina Display tick.

The Rundown On Lines & Pixels

I know this is supposed to be a big article about Retina Displays. However, right now we need to take a little detour. For now, I just want to talk about 1080P/I screen televisions. Everyone wants one, right?

But first off, I’ll go ahead and answer this question: what does the 1080 in 1080P/I mean?

HDTV   How Does The Apple Retina Display Work? [MakeUseOf Explains]

1080 simply refers to the amount of horizontal lines that run vertically up and down the screen. But what about the vertical lines running horizontally? There are 1,920 of those, so let’s multiply them together for fun - 2,073,600. But what does this number mean? This, my friend, is the number of pixels found on the screen.

Furthermore, regardless of how big the screen is, this will always be the same number of pixels. It’s just that the screen areas reserved for individual pixels just get bigger, causing less pixels per inch (PPI). That said, the more PPI, the smaller the 1080 television screen, but the less distinguishable the pixels are.

pixels   How Does The Apple Retina Display Work? [MakeUseOf Explains]

So essentially, with any given high definition television, you get (about) 2 megapixels worth of screen real estate. (Granted, there’s a such thing as RGB subpixels for each individual pixel, but that’s really not worth talking about.) Generally speaking, this just explains how all screens work. You have a set of horizontal lines, and you have a set of vertical lines. These lines converge at multiple points (the pixels), and this sets up your picture piece by piece like a puzzle.

A DPI Experiment

Newspapers (and any printed piece of work) are printed using a variety of dots that build up the resolution of an image. Much like pixels, these dots build up the entirety of the image. The more dots there are, the higher quality the picture. Additionally, they can help with the color grading of the image. Lighter colors feature dots that are further apart while darker shades place them closer together. At that point, it’s mostly the size of the dots that help with the image resolution.

newspaper   How Does The Apple Retina Display Work? [MakeUseOf Explains]

For an experiment, grab a piece of paper (or imagine one), and draw a bunch of dark dots together in the shape of a circle with a radius of about an inch. Make sure the dots are fairly close together, but leave a little space between them. Now tape it to a wall, stand about 6 feet back, and look at the image on the paper. You should see a semi-solid circle.

Now, let’s do something a little different. Draw a circle the same size, but this time, use a larger amount of tinier dots and put them much closer together. Go ahead and stand 6 feet back once more. This time, you should see a much more solid circle. Now move closer – about three feet should do. You should notice that the dots still seem to form a decently solid circle.

DPITest   How Does The Apple Retina Display Work? [MakeUseOf Explains]

Essentially, this is how dots and pixels work with print and digital images. With print pictures, image quality comes in the form of dots per inch (DPI). As you can tell with the image here, the more dots that are in an area, the closer you are able to get to the image without seeing them. That said, the more horizontal and vertical lines that exist on a screen, the higher quality an image.

A Simple Explanation In Layman’s Terms

Apple claims that the human eye’s limit for seeing an image at a distance of about 10-12 inches away is 300 PPI. Granted, this is supposedly based on 20/20 vision, and it certainly is variable, but at least it’s close. That said, the Retina Display resolution for the iPhone 4, 4S, and 5 (as well as the 4th and 5th gen iPod Touches) is at 326 PPI. Basically, this allows for the phones to offer a higher resolution than what the human retina can see. Thus, it appears as though nothing is pixelated whatsoever.

Below is a video featuring the late Steve Jobs explaining the basics of the Retina Display (including the PPI information that I have already stated).

Retina Displays just smashed a few extra pixels into a smaller space, right? Yes, but it gets a little more complicated than that. There is an entirely different unit of measurement for Apple’s Retina Display system: pixels per degree (PPD). Basically, we take two pixels that are at the optimum distance from the eye and are one degree apart from each other. We then add up how many pixels are in this triangle, and that number is the PPD.

iPhone5 1   How Does The Apple Retina Display Work? [MakeUseOf Explains]

For 300 pixels at 10 inches, the PPD should be 53. That said, anything above 53 at the optimum distance of 10 inches is considered a Retina Display. Of course, the optimum PPD varies with the type of screen and the distance viewed. For instance, a 15″ MacBook Pro with Retina Display has 77 PPD but only a 220 PPI. (It’s all about the degrees!)

MacBookPros 1   How Does The Apple Retina Display Work? [MakeUseOf Explains]

Here’s the info for the PPI, PPD, resolution, and optimum viewing distance of every Retina Display device:

  • iPhone 4/4S/4th Gen Touch: 326 PPI, 57 PPD, 960×640, 10″
  • iPhone 5/5th Gen Touch: 326 PPI, 57 PPD, 1136×640, 10″
  • iPad (3rd and 4th Gen): 264 PPI, 69 PPD, 2048×1536, 15″
  • MacBook Pro (15″): 220 PPI, 77 PPD, 2880×1800, 20″
  • MacBook Pro (13″): 227 PPI, 79 PPD, 2560×1600, 20″

MacBookPro 1   How Does The Apple Retina Display Work? [MakeUseOf Explains]

As you can tell, there’s a bit of a pattern where the PPD rises as the PPI falls and the optimum viewing distance increases. It’s rather interesting how it all works out. Of course, this is all at the “optimum” distance. You’ll lose quality if you get a little closer to the screen, but you’d have to get really close for that to happen. Consider the DPI experiment: as you got closer, you began to see the dots the composed your circle.

Of course, there’s the question of how they crammed all of the pixels in there. Well, the fact is that if you try to put pixels too closely together, it can actually ruin the image. In an effort to prevent this from happening, Apple had to develop a manufacturing technique which would allow them to put the tiny pixels at slightly different tiers to prevent them from touching each others’ signals.

Below is another video that briefly explains those details.

How Does It Affect Your Other Media?

You may be thinking, “well, let’s say I have a 2880×1800 screen, but I want to watch a film that’s 1080×1920. Wouldn’t that cause the image to be pixelated?” In theory, it shouldn’t. If you allowed the image to retain its 1080×1920 status while on a 2880×1800 screen, it would be smaller than the actual screen, but the PPI would be as such that you wouldn’t actually see the individual pixels. But what if you blow it up to full screen?

MacBookPro 22   How Does The Apple Retina Display Work? [MakeUseOf Explains]

At a very fine level, I’m sure you could tell that the image has been resized. Even still, and I don’t know about you, but I don’t usually watch movies right up against the screen. I typically sit back with a bowl of popcorn with the screen a good distance away from me. In reference to my circle-on-paper example, you can see that this shouldn’t be a problem.

iPhone5 2   How Does The Apple Retina Display Work? [MakeUseOf Explains]

As an iPhone user, I’ve noticed that the Retina Display allows for me to zoom in on photos at their optimum resolution (but not much further). Additionally, with a 1136×640 screen (turned sideways to be 640×1136), high definition videos definitely aren’t a problem at all.

Regarding vectored images and fonts, there shouldn’t be a noticeable difference whatsoever except for the extreme clarity that these images now have. Rather than being built on pixel information, vectored images and fonts use different sizing methods. Vectors are based on line calculations, and fonts are based on the size that the code tells them to be. Basically, they aren’t locked to a specific resolution as most images typically are. They are flexible!

The Wrap-Up

Essentially, this is how Retina Display works. I’m sorry to burst your bubble, but it isn’t magic. Basically, Apple just crammed a ton of tiny dots into a big space that are too small for your eye to see. This doesn’t take away the cool factor, though.

What are your thoughts on the Retina Display? Has it affected your computer usage or media-viewing experiences at all?

Image Credits: imelenchon, BredaAlvimannmconnors

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48 Comments -

0 votes

Frank Zedmore

Great article! I never actively looked for this information but now I’m glad I have it

0 votes

claudine ratelle

Same here. I never bothered to try to understand it because I thought it was very complex. This article helped me understand. Thanks a lot!

0 votes

Suki

Yes. Like you, I thought the article was very informative.

0 votes

Kyle Taylor

I have a Retina MBP, and I really enjoy looking at crisp text and clean interfaces. But as a web developer, Retina kind of sucks. The reason being that most images on the internet are default 72 dpi, but once you see them on a Retina screen, they start to get a little pixelated/fuzzy.

Another issue is program compatibility with Retina displays. I prefer using the Firefox add-on Firebug, but Firefox doesn’t yet support Retina displays (officially), so I’m forced to either using Chrome tools or just move Firefox to an external monitor.

0 votes

Lisa Santika Onggrid

How fuzzy is it if you’re viewing tiny GIF images? I get it that common low-res images will look worse in Retina?

0 votes

Joshua Lockhart

I’d assume so.

0 votes

Joshua Lockhart

I can only imagine. But hey. Video had to go from SD to HD. I’m sure we’ll see a similar transition happen pretty quickly.

0 votes

Venkateswara Swamy Swarna

I knew most of it but still would like to appreciate the author for a good article.

0 votes

Joshua Lockhart

Thank you so much.

0 votes

Carmen Qing

Such a great article, now I know PPI, PPD, and Retina much better.
And why cannot I favorite the article and keep it in some makeuseof folder, so I can read again later?

0 votes

Lisa Santika Onggrid

What do you mean you can’t favorite this article?
Maybe you’ll want to try services such as Pocket or Readibility.

0 votes

Joshua Lockhart

I’d say just bookmark it. Glad you liked it, though.

0 votes

Ron Lister

evernote is kind of cool to save articles and read them later even if your off line.

0 votes

Timothy Liem

so critical. I always like your articles Josh. this one also is a great thing to clear people’s mind about the so-called retina display.

0 votes

Joshua Lockhart

Well, the idea is pretty great, in my opinion. I sometimes imagine that screens will get bigger with similar displays, and eventually, we’ll have cameras that shoot with matching resolutions. That would be pretty cool.

Thanks for the kind words, though.

0 votes

Ron Lister

Makes me wonder why all the manufacturers don’t cram more pixels into there displays, for higher quality. can’t Imagine how you can pattent how many pixels you put in a display screen.

0 votes

Joshua Lockhart

I’d imagine it’s because most media formats haven’t quite reached that kind of resolution yet. (Granted, with 2K and 4K footage, we’re getting there.)

0 votes

Ron Lister

good point joshua, I would imagine that will catch up soon as well kind of the way it goes have to have a way to display before anyone will invest in a media style like the HD tvs comming out when only a hand full of HD channels were available and same with 3D TV and now with densely packed pixel displays. Now when are they gonna’ come out with those clear flexible roll up computers like Val Kilmer had in the Movie Red Planet.

0 votes

Ron Lister

I have seen the flexible glass technology there going to use in flexible display screens and i’ve seen see through computing i know they can apply gold so thin you can see through it. So maybe that tech is on the way too. What an amazing and terifying time we live in.

0 votes

Amirul Khalis

Good article. Something like this for me once a while is a good read. Hope more article on the technology advancement from you.

0 votes

Joshua Lockhart

Thank you.

0 votes

Brenden Barlow

very interesting. ive always (sorta) known how it works, but never this in depth.

0 votes

Joshua Lockhart

Glad I could help.

0 votes

susendeep dutta

Very nice and interesting article.Higher resolution displays are always preferable and I hope,all laptop manufacturers start to use such displays soon.

I would like to know the optimum size you would consider for a HDTV with 1920 * 1080 resolution to have a PPI of 300 or above.

0 votes

Joshua Lockhart

Hey susendeep. As far as an HDTV goes, I’m not sure. That’s a bit more math than I think I can handle at this second, but I do know it is based on the distance as well.

0 votes

Yiz Borol

Personally retina displays are overblown. I can’t tell the difference between 720p and 1080p, so this retina business seems like a really expensive paper weight

0 votes
0 votes

Kishore Kumar

wow.. now i know what is retina display.. thank you

0 votes

Vysakh P

I am sorry if this is the wrong place to ask a question. Android devices specify screen resolution in dpi. But in this article it is written that dpi is used for print media and ppi for displays. Are they exactly same?

0 votes

Joshua Lockhart

It’s essentially the same. DPI… PPI… it’s all the same. Pixels just happen to be the ink dots of the electronic world.

0 votes

Andrei Bogdan

I don’t own any apple products and I don’t really like ‘em either , but this seems rather interesting .

0 votes

Naval Gupta

Very educational, thanks

0 votes

Paulo Delgado

The retina display sounds a bit gimmicky to me.

0 votes

Joshua Lockhart

I’d say just like everything else.

I hate using television terminology again (these screens are different), but we went from SD to HD. Why? Well, higher resolution, of course!

But here’s the thing: why in the world would we want to go to a higher resolution? Does it benefit us? Does it make society better? Does it turn every full-grown adult cat in the world back into kittens for remarkably better cuddle-times?

Nah.

It’s just a more detailed image. I see the retina display as a platform for higher quality content (we’re not completely there with everything – consider what Kyle Taylor said about web development stuff). But I get where you’re coming from. What’s the point? Well… there isn’t one. It’s just better resolution.

0 votes

Ben Jacobs

helps me understand what Apple is preaching. But I don’t think that is all, look at the new HD displays with over 400 ppi….how does that fit. Well based on what Apple says, then I should be able to use the device closer and have more fluid characters on my display.

0 votes

Joshua Lockhart

Hey Ben,

You have to factor in the 400ppi for what size screen, the optimum viewing angle, number of pixels on the screen… All sorts of stuff. I can’t just say that something is 300ppi and it’s automatically retina. Notice that the MacBook Pros go below 300ppi.

Even still, I’m willing to bet you’ll have more fluid characters at least. However, why would you want to use the device closer than you already are?

0 votes

PhredE

The single most important important word that needs revival on this planet for this context is ‘subtends’. It applies to angles.
Joshua is almost there when using the term PPD, but it would help to think in terms of the arc from your eye to one side of the object you’re viewing, to the other – in this case, your screen.
The expression is ‘The screen subtends and angle of x degrees’, describing the triangle from one side of the screen to the other then to your eye. From there you can derive the pixels per degree, PPD, by simple division. By choosing a standard arc that a measure subtends, we can gauge comparative differences between different types of displays. If the standard is one degree, well and good, but subtending is the concept that embraces the task.

0 votes

Joshua Lockhart

I don’t know how this comment got buried in the pile. Thanks, PhredE. Good info.

0 votes

Rob D.

“1080 simply refers to the amount of lines that run vertically across the screen. But what about the lines running horizontally? There are 1,920 of those, so let’s multiply them together for fun – 2,073,600.”

Someone might’ve brought this up already, but I’m pretty sure you are confusing “vertical” with “horizontal” here. 1080p means 1080 *horizontal* — not vertical — lines.

0 votes

Joshua Lockhart

Hey Rob,

I looked at that and my wording was confusing. There are 1080 horizontal lines that run vertically up (better word than “across”) the screen. However, there are 1920 vertical lines that run horizontally across the screen.

Just weird wording. My apologies.

If I remember correctly, 2K and 4K is in reverse, with the number referring to the vertical lines that run horizontally. Right?

0 votes

Joshua Lockhart

are in reverse*

0 votes

Joshua Lockhart

Rob, I believe we’re about to fix it. Thanks for bringing into my attention.

0 votes

Joshua Lockhart

it* not into*

I’d love to be able to edit comments.

0 votes

Pat Wiegand

So if I understand this correctly, Apple creates a new way of defining their pixel density — instead of using linear geometry (PPI) they use angular geometry (PPD). Then they figure out what viewing distance is needed for their screens to meet their threshold PPD and call it Retina because it meets their own subjectively derived specification! Good trick to confuse the patent lawyers. Once again, Apple takes an existing technology, does very minor changes, and claims it as their own. How dishonest. Hopefully people can see that other manufacturers screens can also meet this “Retina” definition. There is nothing inherently different about the technology. And what is your comfortable viewing distance for an iPhone? Mine is about 6″ not 10″, which would make the PPD much less.

0 votes

zeak

I have a phone that’s 440 poi what would that be translated in pod? And is it to much resolution

0 votes

zeak

I meant ppi autocorrect it can be a curse or a blessing.

0 votes

zeak

I also meant ppd

1 votes

Pat Wiegand

The formula would be:
if X is the viewing distance in inches and R is the points-per-inch resolution, then the angular resolution (PPD is:
PPD = 0.0174 * X * R

In your case, for a 10-inch viewing distance and 440 PPI resolution your PPD is about 77 PPD. Congrats, your display is better than Retina quality!