Motion blur that you see on TVs influences how blurry fast movement appears to be on the screen. For the most part, motion blur manifests as a trail on moving objects and is of particular importance for sports and video games. If you enjoy watching either of those things, it’s important to get a TV with minimal blur.
When evaluating motion blur, we photograph the appearance of blur on the TV and then test for pixel response time.
When it matters
For the majority of TVs, motion blur is really only a potential problem with sports and video games, because of the quick movement inherent to both. With movies and regular TV, you will almost never perceive motion blur other than that which is included in the video, due to the low frame rate and the slow shutter speed of the camera.
Too much motion blur is very noticeable, and can ruin the look of movement on a TV – nobody wants a long trail following a moving object. Beyond those TVs that clearly have way too much blur, the amount of blur that a person will find acceptable is subjective. Some people are much more sensitive than others.
To provide an idea of the way motion looks on the TV, we use a rail-mounted pursuit camera to take a photo of our logo while it moves across the screen. The resulting photo represents what you can expect your eye would see while watching a moving object, and while it’s not a perfect representation, it’s at least a fairly useful example.
In the test, our logo moves across the screen at a speed of 960px per second, and at a frame rate of 60 fps. We slide our camera along the rail at the same speed as the logo, and take a picture with a shutter speed of 1/15 of a second, to capture all artifacts.
To validate that our camera goes at exactly the same speed as our logo, we are using temporal tick marks placed just below the logo. This technique was invented and proposed to us by Mark Rejhon of Blur Busters, a website dedicated to the reduction of motion blur.
You can test your own screen using our test pattern. If you follow our logo with your eyes, you will be able to compare it to our test results. Alternatively, you can find a wide variety of motion tests over at TestUFO.com.
100% Response Time
Response time is the amount of time it takes a TV’s panel to change from one color to another, and it’s a pretty big part of the blur we see on TVs. With a long response time, the pixels can’t quite keep up with moving objects, and so you can see a lengthy trail of blur following behind them. Above, you can compare a long response time (left) to a short response time (right), and you can see that the difference is a pretty big one.
To test for response time, we use an array of photodiodes connected to an Arduino Due board, which is itself connected to a computer through USB, to record how quickly a TV is able to make transitions between different shades of gray. Every shade corresponds to a different level of luminance output, and so when a TV switches from one shade to another, the screen’s luminosity must also change. The amount of time it takes a TV to make this change in luminosity is the response time, which is measured in milliseconds.
Once we have performed this evaluation for each of the transitions we test, we take the times for each completed transition and average them out, which gets us our global response time number. Note that some transitions may have a lower response time than the average we list, meaning less blur for those changes, and others might take a good deal more time, creating more blur in those cases.
80% Response Time
The methodology used to determine the 80% Response Time is the same as for the 100% Response Time, as described in the previous paragraphs.
In the chart above, a transition between 20% gray (dark gray) and 80% gray (light gray) begins at the vertical red line and is complete at the vertical green line. The vertical orange line represents the moment when screen luminosity has completed 80% of the transition to its target state, which in this case represents a 68% gray level (20% + 0.8*(80%-20%) = 68%). The luminosity level of 20% gray is represented by the horizontal red line at the left, the luminosity level of 68% gray is represented by the horizontal orange line, and that of 80% gray by the horizontal green line at the right. The time it takes the luminosity to change from the red to the orange line represents the duration of the 80% response time, and from the red to the green line represents the length of the 100% response time. The 80% response time is a good indication of the smoothness of movement, with shorter response times making movement clearer and longer response times making movement smoother, while also adding short but apparent trails to moving objects. The 100% response time is a good indication of how long the faint trails following moving objects will appear.
You can see that the transition between shades/luminosities surpasses the level required by the 100% response sooner than our response time measurement would indicate. However, this is a temporary overshoot, and the transition is only considered complete when the luminosity is stable at the new level. Tests done prior to 2017 considered this overshoot separately from the response time, but overshoot is perceptually very similar to a transition being incomplete, with both phenomena adding visible trails behind moving objects. Overshoot shows trails that are lighter than the background behind moving objects, while a slow transition adds trails that are darker than the background.
Elements of motion blur
Motion blur is created by several things:
- Response times, which represent how long it takes a TV’s pixels to change from one color to another. Longer times equate to longer blur trails on moving objects.
- Frame time, which represents the amount of time for which a frame is displayed on the screen. The longer the frame time, the more blur you will see. See more information about this manifestation of motion blur here.
- Blur within the video itself. This results from the on-camera action outpacing the camera’s shutter speed. Cinematographers usually keep this kind of blur in mind and will account for it when planning shots for the movie or show. The result will usually be that you don’t even register that the blur is there.
How to get the best results
Most elements of motion handling are static. For example, response times can’t be changed through settings, and so those elements of motion blur cannot be improved.
If you have the option to do so, watching media with a higher frame rate will help you avoid blur. Some TVs may also have a couple of settings that can improve other elements of the motion blur, though you should be aware that they each have their own downsides. We list those settings below.
- Motion interpolation enhances the frame rate of video by creating and inserting transitional frames between the original video’s existing frames. This reduces frame time and creates a smoother look overall, but some find the result undesirably similar to the look of a soap opera. What’s more, since there is no improvement to the response time of the pixels, the length of the trail on moving objects doesn’t change. We talk more about the pros and cons of motion interpolation here.
- Some TVs have the option to introduce backlight flickering, or insert black frames, in order to shorten frame time and clarify movement. This also has the effect of dimming the maximum luminosity, though. As with motion interpolation, this does not affect response time, so the length of the trail on moving objects does not change. See more information about the effects of flicker here.
- By nature of the technologies, LCD panels (LCD and LED TVs) have relatively long response times, and OLED panels have much shorter ones.
- A video with a higher frame rate will only have less blur than an identical video with fewer frames if the TV’s refresh rate is capable of matching that frame rate (ex: a 120 hz video on a 120 hz TV, not on a 60 hz TV).
- Similarly, a TV with a 120 hz refresh rate will not have less blur than a 60 hz TV if the video’s frame rate is not also higher than 60 hz. With 60 hz video on a 120 hz TV, the video signal will still only be 60 fps, which means the frame time has not changed. The same applies for 24 hz and 30 hz on TVs with higher maximum frame rates.
- Refresh rate also does not have any effect on response time.
- It’s impossible to compare response times listed by different manufacturers and reviewers without knowing the testing methodology. We test several gray-to-gray transitions and present an average, but some manufacturers and reviewers will only list the shortest response time the screen is capable of, or they might test the time it takes to go from one shade to another, and then back. Unless you can compare the entire methodology, the results won’t match up in a fair way.
Motion blur makes fast movements look less clear, which can be an annoyance for sports fans and gamers. If you watch either of those things, it’s important to get a TV with minimal blur. To get a good idea of how much blur TVs have, we test them for their pixel response and overshoot times.
Your best bet for getting a TV with little blur is to find a model with low response time. You can also help reduce the amount of blur you perceive by watching higher-frame-rate videos, or by enabling motion interpolation or backlight flickering features. Just remember that enabling these sorts of extra features can introduce other issues to the video.