If you watched Apple's big 2018 iPhone unveil last night, you might have heard a very interesting number floated around: a 120 hertz display rate.
This may not speak much to you, but if you are a gamer, you probably know the difference that a screen with a faster refresh rate can make.
Here is the thing, though: the new iPhones do NOT actually have a 120-hertz refresh rate on their displays. The only phone that has that feature is the Razer Phone
, a phone – not coincidentally – aimed at gamers.
So what did Apple mean when they mentioned the 120-hertz number?
To understand that, we need to understand the difference between something called a touch sample rate and a different term: the touch delivery rate. The new iPhones – all three of them, in fact, the iPhone XS
, XS Max and the XR – have a 120-hertz touch sample rate, but still run on a regular 60-hertz refresh rate. In other words, the screens track you at 120-hertz, but refresh the display at 60 hertz. Still confused? To understand what this means, you simply need to understand that the hertz rate is a different way of saying how often a screen registers input. At 120 hertz, the interval is twice as short and the screen tracks movement every 8.3 milliseconds, while at 60 hertz it does the same tracking every 16.6 milliseconds. This way, having a faster tracking
rate means that the screen can register your touch and respond by starting to render the next frame in an animation just in time for the next 16ms refresh
There is a difference between tracking rate and refresh rate
If we had a 60-hertz tracking rate and a 60-hertz refresh rate, the tracking would end at the same time as the refresh interval, so the actual rendering of the animation would start one interval later. The end result in the new iPhones is that animations start faster and appear smoother, but this is not to be confused with a 120-hertz refresh rate. All of that also puts a bit of extra load on the system chip, so having the most powerful mobile chip on the new iPhones certainly helps.
So this should clear up all the confusion around the tracking rate and the refresh rate of the new iPhones.
Look at the table right below and you would see that the iPhone X
actually has the same 120-hertz tracking and 60-hertz rendering, and it was the first actually the first iPhone with a faster tracking
rate. The 120-hertz refresh rate is available on an Apple product that you can buy today, but it's Apple's iPad Pros and not an iPhone.
Do you have any questions around all of this? Feel free to share them in the comments below and we'll do our best to answer.