How We Calculate Stutter On Dozens Of TVs Each Year

Unlike most of our tests, stutter isn't measured directly on the TV. Instead, it's calculated from the TV's response time. 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 before transitioning to the next frame.

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.

Why Do Modern TVs Have Stutter?

We mentioned above that stutter is directly related to a TV's response time, but why is that? It's all about the panel technology. Modern TVs all use a technique known as sample-and-hold to display an image. This means that once the pixels that make up a TV's image have drawn a frame, they remain static until it's time to draw the next one. It takes some time for a pixel to change from one color to the next; that time is known as its response time. The faster the response time, the longer that pixel remains fixed until it's time to change to the next color. The human eye doesn't expect motion to jump this way from one frame to the next; it expects motion to be fluid, so the longer the frame is held static on the screen, the more it'll appear to stutter.

This differs from older TV technologies like plasma and cathode ray tubes, which used short light bursts to produce an image instead. These older technologies are completely stutter-free, as they don't use sample-and-hold at all. This means that if you're upgrading from a plasma TV, for example, you'll likely be even more sensitive to stutter, and TVs with fast response times like OLEDs may actually appear to have worse motion handling than your much older plasma.

You can learn more about stutter and motion in general through our series of videos on our Home Theater YouTube channel, starting with the first entry linked below.

How To Get The Best Results

While you can't change the TV's response time, there are a few settings that can 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 reduces the total time 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. 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

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.