Our TV Motion Tests: Stutter

Stutter is an artifact of motion that happens when a frame stays on the screen for too long. It can be bothersome while watching movies or low frame rate content because the TV has to hold each frame on longer. Stutter has an inverse relationship with the response time of the TV; the quicker the response time, the more stutter there is, while slower response time results in less stutter.

We calculate the stutter time after testing for the response time, using a simple formula to find out how long the stutter is.

Test results

When It Matters

If you watch lots of movies or low frame rate content, it's important to have a TV that doesn't stutter much. Not everyone notices stutter, but if you do, you'll notice that camera movement looks jarring and uneven during long panning shots. Stutter has an inverse relationship with the response time, so it's often a trade-off between having little stutter or a quick response time, but since there are ways to help reduce stutter, having a TV with a quick response time is always a better choice.

Below you can see an example of stutter. The TV on the left has a quick response time, so there's no motion blur behind fast-moving objects, but the shot looks more jarring as each frame is held longer. On the right, the response time is much slower, so there's blur trail behind the ball, but the overall movement in the shot is smoother. You should easily see the difference if you pay attention to the plant in the foreground.

Our Tests

We calculate the stutter following the response time test. The response time is the amount of time it takes for pixels to change from one color to the next. However, if the colors transition too quickly, they stay on the screen for a few milliseconds before transitioning to the next frame. For example, if you show up to a meeting early, it means you can get there fast, but you'll have to wait more time compared to someone who's slow and shows up right on time.

For the stutter tests, we calculate it for 24 and 60 fps content, but you can also use basic math if you want to find out the stutter with 30 fps content.

Frame Hold Time @ 24 fps

For 24p content (like movies), the signal sends 24 frames every second. Since there are 1000 milliseconds in a second, each frame is held on for 41.67 ms. To calculate for stutter, we simply take that time and subtract the TV's 100% response time from it. Using the Vizio V5 Series 2021 as an example, it has a 15.6 ms 100% response time; since 41.67 minus 15.6 ms is 26.1 ms, the stutter is 26.1 ms. This is the amount of time the image stays on the screen before transitioning to the next frame, which is the cause of stutter. We use the same calculation for every TV.

Frame Hold Time @ 60 fps

We use the same formula for the frame hold time @ 60 fps. This is more important for higher frame rate content like games. TVs with a slow response time rarely have an issue with stutter here because the colors don't transition too quickly. For 60 fps content, the frame time is 16.67 ms. Looking at the LG G1 OLED, for example, it has a near-instantaneous response time of 2.4 ms, so using basic subtraction, it has a stutter of 14.2 ms. OLED TVs have worse stutter compared to LED TVs because they have such a quick response time.

Additional Information

Causes of stutter

Stutter is caused by two main factors:

The response time, which affects the amount of time each frame is held. As mentioned earlier, a quicker response time results in more stutter, while a slower response time results in less stutter.
The frame rate, as a higher frame rate results in less time needed to hold each frame, which can help reduce stutter. Generally speaking, a higher frame rate can help improve the appearance of motion.

How To Get The Best Results

While you can't change the response time of the TV, there are a few settings to help reduce stutter if it bothers you.

Motion interpolation

Motion interpolation is probably the best way to reduce stutter. This feature increases the frame rate of the video signal to a higher one. If you have a 120Hz TV and you're watching 30 fps content, increasing the frame rate can help reduce stutter because each frame isn't held on for as long. It doesn't change the response time, but it does reduce the total time that each frame remains on the screen.

Learn more about motion interpolation

Backlight strobing

Some LED TVs have a feature called backlight strobing, which is also known as black frame insertion (BFI) on OLEDs. LED TVs can flicker their backlight to help reduce the amount of blur trail behind each object. Although this isn't a direct way to decrease the amount of stutter, it decreases the amount of time each frame is shown on the screen for. Overall, the point of the BFI feature is to improve the appearance of motion.

Learn more about black frame insertion

Judder removal

Judder and stutter, although they sound similar, aren't the same thing. Stutter is about the amount of time each frame is held on for after the pixels transition, while judder is an inconsistent frame time.

Learn more about judder

Other Notes

When comparing OLED and LED TVs, OLEDs have more stutter because they have a near-instantaneous response time.
Try watching high-frame-rate content as much as possible if stutter bothers you. There can be a lot of stutter with low frame rate content, especially with TVs that have a fast response time.

Conclusion

Stutter can be a distracting motion artifact while watching low frame rate content. It happens when the TV has a quick response time, as the pixels transition colors quickly, but then the TV has to hold the frame for a few milliseconds before showing the next. We measure stutter using a simple calculation from the response time, as stutter and the response time have an inverse relationship. There are a few settings to help reduce the amount of stutter, like motion interpolation, but the best way is to watch high frame rate content.