Motion interpolation is a feature that increases a video’s frame rate, usually up to the maximum frame rate of the TV. This has the effect of making movements look smoother, clearer, and more lifelike than what you typically see from movies and TV – pretty similar to the look of movement in soap operas (hence the alternate name of ‘soap opera effect’). This feature only matters if you want to be able to make movement in videos look a bit smoother.
We test all our TVs to see whether they are able to interpolate 30 fps and 60 fps video. Only 120 hz TVs will be able to interpolate 24, 30, and 60 fps video up to a higher frame rate, but some 60 hz TVs are able to interpolate 24 and 30 fps video.
When it matters
Whether motion interpolation matters is entirely down to personal preference. If you like the idea of making the movement of videos smoother than what you normally see, you should get a TV that can enable motion interpolation. If you don’t want that feature, don’t worry about it, but also don’t avoid getting a TV purely because it has interpolation capability – you can always disable it.
Sensitivity to motion interpolation varies a lot from person to person. Some people really enjoy the look of it, and others really hate it. Some don't notice the difference until it is pointed out. Overall, this feature really isn’t essential – most people will get by just fine without motion interpolation – but it could be a nice bonus for those who like it. To get an idea of what it looks like, take a look at this video. You can't see the difference in real time, because YouTube's maximum frame rate is 60 fps, and therefore cannot represent 120 fps footage. However, in slow motion, you can clearly see the added frames you get with motion interpolation.
Motion interpolation (30 fps)
To pass our Motion Interpolation (30 fps) test, a TV must be able to interpolate, or smooth, a 30 fps video by increasing the frame rate up to at least 60 fps.
The results of this test reflect whether a TV is able to add smoothing to 30 fps video sources, like regular TV shows, most streaming videos, and some video games. It also means the TV will be able to smooth video with a lower frame rate than 30 fps (like 24 fps movies). Because most of the video we watch is 24 or 30 fps, this motion interpolation test is the more important of the two we conduct.
To test for this capability, we play a 30 fps video on the TV and then look for a setting that smooths out the video. Above and on the left, you can see a photo of unsmoothed 30 fps video, and in the middle, a photo of the same video after it has been interpolated on a 60 hz TV. For the sake of comparison, on the right is an image of the original footage interpolated on a 120 hz TV. You can see the video has been smoothed significantly more by the 120 hz TV, and it’s worth noting that you can't typically control the 'amount' that most TVs will interpolate. Most 60 hz TVs will interpolate video to a similar degree, and the same is true of 120 hz TVs.
Motion interpolation (60 fps)
Similar to our 30 fps interpolation test, we test TVs for the ability to smooth 60 fps videos. To pass, a TV needs to be able to increase a 60 fps video’s frame rate to 120 fps.
The results of this test reflect whether a TV is able to add smoothing to 60 fps video, like sports, some video games, and some streaming videos. Because 60 fps video is relatively rare, this test isn’t quite as important as our 30 fps interpolation test. It’s worth noting, however, that a TV that passes this test will be able to smooth 24 and 30 fps videos even more than a TV that only passes the 30 fps interpolation test.
To test for this capability, we play a 60 fps video on the TV, and then see if there is a motion interpolation setting that will make the video look smoother. Above on the left, you can see a photo of the unsmoothed 60 fps video, and on the right, a photo of the same video after it has been interpolated to 120 fps. Note that 60 hz TVs cannot interpolate 60 fps video to a higher frame rate, and so will always fail this test. We use this test to help determine whether a TV’s refresh rate is 60 hz or 120 hz.
How motion interpolation works
Most media is recorded at 24 frames per second, 30 fps, or 60 fps. Without interpolation, if a video’s frame rate is lower than the refresh rate of a TV (30 fps on a 60 hz TV, for example), the TV will show each frame multiple times, thereby getting the video to ‘fit’ the refresh rate. When this happens, the video looks the same as it would if the TV’s refresh rate was as low as the video’s frame rate. 24 hz video is a special exception, which we discuss in detail here.
Motion interpolation offers an alternative use for the difference between video frame rate and TV refresh rate. Instead of playing each frame multiple times, the TV’s processor will enhance the frame rate of the video by creating transitional frames and inserting them between the original frames. This makes the video match the TV’s refresh rate, but also makes it so that the movement of the video looks smoother. The image above offers a basic idea of what this looks like.
Motion interpolation's downsides
Many people appreciate the increased fluidity of interpolated video. However, motion interpolation has three main downsides:
- Cinematographic purists complain that it kills the film experience and runs counter to the traditional look of movies, making videos look so realistic that it becomes unrealistic. This is why some people call this the ‘Soap Opera Effect,’ as interpolated video looks similar to the way soap operas traditionally have.
- The interpolated frames could contain errors or distortions because they were generated by a computer, which is not the same as if the camera was really capturing a high frame rate.
- The processing takes a certain amount of time to execute, which increases the input lag. This makes interpolation unsuitable for gaming.
Motion interpolation & motion blur
One of the main reasons people enable motion interpolation is to reduce the amount of blur on the TV. The higher frame rate reduces the length of time each frame appears onscreen, which helps improve clarity. It’s important to note, however, that while movement will become clearer, the length of the blur trail on moving objects will not change. The trail corresponds to the pixel response time, which is unaffected by motion interpolation. We discuss different elements of motion blur in greater detail on this page.
How to improve it
There are a few TVs that provide you with sliders that can let you fine-tune the amount of interpolation applied to video, which can help you get a look that is better tailored to your specific preferences. Others just have presets that you can choose from. Ultimately, there is no way to improve the functionality of motion interpolation apart from choosing the amount of interpolation that best corresponds to what you like. For the smoothest picture, choose the maximum interpolation settings. If you don’t want interpolation, just turn it off.
Here are the settings you must adjust to enable or disable motion interpolation on TVs from various brands.
Samsung: Go to Menu > Picture > Picture Options and enable/disable 'Auto Motion Plus.'
Sony: Go to Menu > Picture adjustments > Advanced settings > Motion and enable/disable 'Motionflow.'
Vizio: Go to Menu > Picture > More Picture. Adjust 'Reduce Judder' to adjust smoothing on 24p and 30p video. Adjust 'Reduce Motion Blur' to adjust smoothing on 60p video.
LG: Go to Menu > Picture > Picture Mode Settings and enable/disable 'TruMotion.'
- Some TVs have an option to make the backlight flicker. This also clarifies motion, but won't make movements look like what you see in a soap opera. It does, however, dim the backlight, and sometimes you can notice the flickering of the light.
- Some TVs have difficulty smoothing out videos and will skip frames on occasion. If your TV does this and it bothers you, the best option is to just disable motion interpolation altogether.
Motion interpolation is a feature that allows a TV to smooth the movement of videos. It applies equally well to all video you might watch on a TV, and while it’s not hugely important in general, some people do feel quite strongly either for or against the look of interpolated video. Our tests in this area allow us to see whether a TV is able to interpolate a 30 fps video, and also whether it is able to interpolate a 60 fps video. To get the best results from your TV, simply enable or disable motion interpolation, according to your preference.