What does refresh rate of display mean

When it matters

When displaying 30 or 60 fps content

A 60 fps video played on a 120Hz TV will look almost identical to the same content played on a 60Hz TV. In a case like this, the TV either adjusts itself to match the refresh rate of the source, which effectively turns it into a 60Hz TV, or it simply doubles every frame.

As you can see from the picture above, a TV with a higher refresh rate does not produce less motion blur. Since both of these TVs have a very similar response time (which causes the blur), 60 fps content results in an almost identical picture.

To better showcase these differences, we compared two TVs side-by-side; a 60Hz model, and a 120Hz model, with similar response times. We filmed these TVs in slow motion to easily compare each individual frames.

When displaying 24 fps content

While a 120Hz TV doesn't inherently produce better motion, it can provide a few advantages over standard 60Hz TVs. One of the most important advantages is the ability to play back content that is meant to be displayed at 24Hz. Most TVs, including 60Hz TVs, can simply adjust the refresh rate of their panel to fit the source, but some devices (such as Chromecast) can only output at 60Hz, regardless of the content being played. This can lead to issues since 24 is not a multiple of 60Hz. To display this sort of content, a technique known as a "3:2 pulldown" is used. Basically, the frames alternate between being repeated 3 times and 2 times. Not everybody notices this, but it causes some scenes, notably panning shots, to appear juddery. 120Hz TVs can avoid this entirely since they can just display each frame 5 times. Some 60Hz TVs can manage to do it, but if this is an important feature for you, you will probably have to get a 120Hz model. Learn more about judder and our related tests, and see a list of judder-free TVs.

When displaying 120 fps content

If your TV supports a 120Hz input, and it is connected to a PC or Xbox One, then this is where having a 120Hz TV can be a strong advantage. While it is rare to find content other than games with this frame rate, there is a significant impact on the perceived motion.

As you can see, the 120 fps picture is much clearer. This is because the 120 fps frames stay on screen for half the time of 60 fps frames. When your eyes track a moving object across a screen, it blends the two frames together. Since the 120 fps content has twice as many steps, it doesn't produce as much blending (this is called persistence blur).

When using the motion interpolation feature

Another place where 120Hz is useful is if you enjoy the motion interpolation feature found on TVs (also known as the soap opera effect). Most TVs have this feature, even 60Hz ones, but since motion interpolation works by adding generated frames between existing ones, having a higher refresh rate allows you to have twice as many extra frames. This allows the TV to make better interpolated frames as it can spread the movement into more precise steps.

Another useful feature of a higher refresh rate is the ability to use motion interpolation on 60 fps content. Since they cannot display more than 60 frames per second, a 60Hz TV can't use its soap opera effect feature on content with higher frame rates. A 120Hz TV has the advantage of being able to add an additional interpolated frame between each of the 60Hz ones, since it is capable of displaying twice as many. Unless you have a 120Hz TV, you will only be able to use this feature on 24p or 30p content.

Black frame insertion

There are other ways to produce a similarly clear image as a 120Hz refresh rate. Many, if not most, TVs these days have a feature called black frame insertion. Essentially, the TV displays each frame for a shorter period of time, with a black screen in between each frame. On most LCD/LED TVs, this is achieved by adjusting the flicker frequency of the backlight; which results in the backlight being turned off for half the frame. On OLED TVs, which don't have a backlight, this is done by actually inserting a black frame for half of the frame time.

Persistence blur occurs when your eyes move past a static image, such as each static frame that makes up moving content. With black frame insertion, the static frame is present for a shorter duration, so the length of the persistence smear is shorter. Unfortunately, though, not everyone can stand the flickering, and most people get annoyed after a while.

Different refresh rate from different sources

A TV is only as good as the content you are playing, and unfortunately, very little 120 FPS content actually exists. No online streaming service officially supports it, and the only sources that use that refresh rate are PCs, a recent Xbox One, or Apple's iPad Pro. We've compiled a couple of lists of common entertainment sources as well as their respective refresh rates.

ContentFrame Rate
Netflix24 fps to 60 fps
Amazon Video24 fps to 60 fps
Blu-ray Movies24 fps
YouTube30 or 60 fps
Cable/Broadcast TV (NTSC)30 or 60 fps
Cable/Broadcast TV (PAL)25 or 50 fps
SourceRefresh Rate
Xbox One S/X24Hz to 120Hz
PS4/PS4 Pro24Hz to 60Hz
Blu-ray players24Hz to 60Hz
PCUp to 240Hz
Chromecast60Hz
Apple TV24Hz to 60Hz

Conclusion

For most people, there is little benefit to upgrading to a TV with a 120Hz refresh rate. Unless you have 120 fps content, there is very little difference between a 60Hz and a 120Hz TV, unless you enjoy the Soap Opera Effect, where the missing frames are interpolated to make 24 or 60Hz content look like it is 120Hz.

The exception to this is gaming. As gaming can generate content on the fly, it can easily scale to any refresh rate (assuming your PC can keep up). 120Hz gaming is growing rapidly in popularity and is now supported on the Xbox One with a 1080p or 1440p resolution. As HDMI 2.1 devices arrive on the market, 120Hz gaming is expected to continue growing in popularity, as HDMI 2.1 allows for gaming at 4k @ 120Hz.

Black frame insertion feature enabled (Sony X950G)