Explainer

You’ve seen the term in Mac names—iMac with 5K Retina display, MacBook Pro with Retina display, and so on. But what is a Retina display, and why should you care? The short answer is Retina displays are high-resolution screens on which graphics are extra sharp and text is super crisp. Here’s the longer answer.

First off, a little background. The LCD screens used in Apple’s displays use a grid of “pixels”—the smallest possible dot whose color can be controlled—to create all the text and graphics you see. The first Mac needed 72 pixels in each direction to draw a 1-inch square, giving it a pixel density of 72 pixels-per-inch (ppi). Thanks to manufacturing advances in screen technology since 1984, the iPhone 6s Plus screen can fit a stunning 401 pixels into each inch. As pixel density goes up, the pixels get smaller. With a 72 ppi screen, it’s easy to see each individual pixel in a character, and the higher the pixel density, the harder it becomes to pick out separate pixels.

Low-and-High-resolution

When Steve Jobs unveiled the iPhone 4 in 2010, he said that for a screen that’s held 10 to 12 inches from the eye—about the distance at which many people hold their iPhones— the human eye can’t resolve individual pixels if it’s about 300 ppi. At longer distances, it becomes harder to discern small details, so most people won’t be able to pick out pixels on a screen viewed at arm’s length, such as an iMac display, if it’s about 220 ppi.

A “Retina display,” then, is any screen whose pixel density is high enough that someone with 20-20 vision cannot see individual pixels at the standard viewing distance used for that device.

For the Mac, the necessary pixel density for a Retina display is about 220 ppi. Larger iPads have a pixel density of 264 ppi, and the iPad mini checks in at 326 ppi. From the iPhone 4 through the iPhone 6s, pixel density stayed at 326 ppi, but the iPhone 6s Plus upped it to 401 ppi. The tiny Apple Watch screen is about 330 ppi.

Practically speaking, a Retina display looks better than a non-Retina display. Put a 27-inch iMac with 5K Retina display (218 ppi) next to a non-Retina 27-inch Thunderbolt display (109 ppi), and the difference will be noticeable, particularly with text. If you suffer from eyestrain, reading on a Retina display will likely be easier and less tiring, since the words will be clear and crisp, without any of the fuzziness on the edges that you see on lesser displays.

Happily, there are few decisions to make when it comes to Retina displays. All recent models of the iPad, iPhone, iPod touch, and Apple Watch have Retina displays, so you’re good there. In the Mac world, however, not all MacBook models have switched, and Apple still sells some non-Retina iMacs and the non-Retina Thunderbolt Display. Plus, not all Macs can drive an external display that would be equivalent to a Retina display, even if Apple were to update the Thunderbolt Display to Retina. So if you’re buying a Mac now and there’s a choice between a Retina and a non-Retina option, be sure to compare them in person before deciding.

One last thing. It’s important to realize “Retina display” is an Apple trademark. So you won’t see any other manufacturers talking about their products as having Retina displays.

When you read an email message on your iPhone and delete it, do you have to trash it again when you check mail on your Mac? Or is your email kept in sync such that if you delete a message on one system, it never even appears on the other?

If you fall into the first camp, your Internet service provider probably has you using an email technology called POP. Conversely, if you’re in the second camp, you’re probably using a different email technology called IMAP. Don’t worry what POP and IMAP stand for—they could be called Fred and Jane for all that it matters. What does matter is that if you’re using POP to read email on more than one device, you’re wasting time and effort.

Put simply, POP was designed in 1984 so that every email message would be downloaded from your mail server and immediately deleted from the server, so the only copy would exist on your Mac. But that made it impossible to check email from more than one computer, so POP’s designers made it possible for a message to be downloaded but not deleted, so it could be retrieved again by another computer. But the POP server has no way of knowing that the message was transferred multiple times, so each computer that gets it sees it as a fresh message, forcing you to delete or file it in each place.

In contrast, IMAP, which came along just a couple of years later in 1986, was designed to keep all your email on the mail server itself so multiple computers could access the same set of messages. And, most important, anything you do to a message—delete, file, or reply—in your email app on one computer also happens on the IMAP server, so if you check email from another computer, your email collection reflects all those previous actions.

Fast forward to today, where you might check email with your Mac at work, with your iPhone while at lunch, and on your iPad at home. If your Internet service provider is using IMAP, anything you do on any of your devices is reflected on all the rest. As an extra bonus, you can search through all your email at any time, from any device, which is great when you realize you need the address for today’s meeting after you’re in the car.

But some ISPs still rely on POP, and for those of you who have had the same email account for many years, even if your ISP supports IMAP, they may not have switched you over. If your email is stuck in the POP past, call your ISP and bring your email into the 21st century. If they aren’t willing to help, remember that you can always use your free iCloud email account instead or sign up for a free account with Gmail or Yahoo.

For those who are shaking your heads because you don’t want some IMAP server in the cloud to hold the only copy of your precious email, rest assured that it doesn’t have to be that way. By default, Apple Mail downloads a copy of every message and keeps it locally on your Mac too, so even if something bad were to happen in the cloud, you’d still have your local copy and your backups of it.

Life is too short to waste time dealing with the same email messages on multiple devices. Computers and smartphones are supposed to make things easier, not harder, so if you’re not already using IMAP for email, do yourself a favor and switch.

Strong Solutions

Category Archives: Explainer

What’s a Retina Display?

Why IMAP Is Better than POP for Email