HOW IT WORKS
120Hz displays: faster-refresh rates explained
YOU WILL LEARN You will learn why faster displays can be worth having
In early 2021, there was excitement over a newly unearthed Apple patent for mobile device displays with refresh rates of 120Hz, 180Hz or even 240Hz. The patent fits with multiple rumours that the iPhone 13 will have a 120Hz display. But what does that actually mean?
What refresh rates mean
Whenever you look at something on an electronic screen, you’re actually watching a succession of still images. Those images work just like the celluloid frames of pre-digital cinema: they flash by so quickly that your brain doesn’t see the individual images; it sees objects in motion instead. The faster the frames flash by or the images are updated digitally, the smoother the movement.
Everybody Hertz
Typical displays today, including the iPhone, your Mac and most iPads, have a refresh rate of 60Hz. Hz is short for Hertz and it’s a measurement of frequency, in this case how many times something happens per second. So a screen with a refresh rate of 24Hz is updated 24 times per second; if it’s 60Hz, it’s updated 60 times a second; and if it’s 120Hz, the screen is updated 120 times per second.
The reason so many displays run at ‘just’ 60Hz is because that speed is actually good enough for most things. But, increasingly, we’re seeing even faster displays, especially in gaming. The more updates per second, the smoother the animation or video.
Less lag and instant illustration
There’s another benefit to faster displays, and that’s their response time. The gap between doing something and seeing it on screen is known as input lag, and with a 60Hz display you can’t get that below 16.67 milliseconds: the screen can’t update any more quickly. With a 120Hz display, that figure drops to 8.33 milliseconds – so not only are the visuals smoother, but your device or an input device such as your Apple Pencil is more responsive too. When you’re playing a very busy online game, that can literally mean the difference between life and death for your character.
More than just a number
120Hz displays have been common in gaming for some time now, and they’re increasingly common in smartphones too: it’s another number to stand out from rivals in a product comparison. But there are genuine benefits beyond gaming, which is one of the reasons the ProMotion display in the iPad Pro is 120Hz when other iPads only have 60Hz. It makes the drawing, animation and movie experience so much smoother.
If 120Hz displays are so great, why hasn’t Apple embraced them for everything? There are several reasons for that. The first and most obvious one is that 60Hz is good enough for most people right now, so there’s no pressing need to go quicker. And the second, more important point is that driving a display twice as fast means draining the battery more quickly. That’s a real concern with thin smartphones in particular because they lack room for larger batteries.
Battery tech hasn’t improved that much, but nevertheless we’re seeing lots of manufacturers such as Samsung put 120Hz screens into their devices without ending up with horrific energy efficiency. The secret? Something called Adaptive Refresh. With Adaptive Refresh, your 120Hz display doesn’t run at full speed all the time. It runs at a lower refresh rate – sometimes lower than 10Hz – when it can get away with it, for example when it’s only showing the time and the weather forecast. When you unlock the phone the refresh speeds up to something around 60Hz, and when you launch a game it ramps up the refresh rate to full speed. It’s an eminently sensible solution to the battery problem: you simply don’t need to run your display at full speed all the time.
That’s exactly what Apple’s ProMotion does. When you need full speed, for example when you’re drawing with Apple Pencil, you get the fast input response and silky-smooth animation of a 120Hz display. And when you’re watching cat videos on YouTube (30fps) or a blockbuster movie (24fps), you’re not making your iPad Pro run at a refresh rate your source can’t make use of.
You’ve been framed
Did you notice we changed our measurement units? One minute we were talking Hertz; the next, fps. Fps – frames per second – dates back to analogue cinema and tells you how many frames per second your film or video uses. It’s purely about the content, not the display you’re viewing it on. For example if you watch a typical movie on a pre-HD CRT TV, the movie was filmed at 24fps and your TV might be refreshing at 30Hz; the same film on an HD TV, iPhone 12 or Pro Display XDR is still 24fps but your display is refreshing at 60Hz (or more in the case of the TV), and so on.
Will Apple bring ProMotion to the iPhone and the Mac? Rumours suggest we should see it in the iPhone 13 Pro and Pro Max alongside a more energy-efficient LPTO display and an A15 chip that delivers 15-20% better power efficiency. As for the Mac, it’s possible… but if Apple’s planning it it’s managed to keep it awfully quiet. Carrie Marshall