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Home / Tips and Tricks / Up to 120 Hz and beyond: The advantages and disadvantages of reducing motion blur on 4K TVs

Up to 120 Hz and beyond: The advantages and disadvantages of reducing motion blur on 4K TVs



Your TV looks soft and it's your brain's fault. With luck, you did not notice. But if you read this, you probably will. I'm sorry.

The problem is called "motion blur," and TV makers have come up with ways to fight it for years. Unfortunately, these methods often have side effects that are worse than cure for many people.

Take Tom Cruise . Together with many movie fans, he hates the soap opera effect that makes films in motion look buttery, similar to soap operas. TV makers have developed this effect to counteract motion blur and often associate it with refresh rates of 1

20 Hz .

High frame rates and motion smoothing are just the beginning. Numerous other blur prevention technologies, including LED Backlighting Scanning and Black Frame Insertion are found on today's televisions. If you know the pros and cons of each one, you will get a TV picture that makes you happier. At least happier than before, when I ruined the televisions for you.

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What is motion blur?

Motion blur is when something on the screen becomes blurry and less clear when it moves. This can be a single object, like a ball or a car, or the entire screen, as if the camera was panning over a landscape.

I always notice when there is a close-up of a face, and then the person turns away. In a second you can see every eyelash and crease, in the next it is a blurry mess.

Some of this can be attributed to the lower frame rate of movies and most television broadcasts, which can lead to blur caused by the camera. You can not change that. There are also blurs caused by the TV itself, which you – to some extent – can use to remedy the situation.

  Dolphin Motion Blur 2019 Redux

A still image that was edited to imitate motion blur. Note that the bottom 1.5 dolphins are softer than the others.


Geoffrey Morrison / CNET

In the early days of flat panel televisions and displays, the culprit was often the slow speed of liquid crystal elements that produce an image on an LCD television. Nowadays most LCDs can change their status so fast that motion blur is caused by something else: "sample and hold".

LCDs – and modern OLED televisions – configure their pixels to display an image and then ] Hold this image until the screen is refreshed. For most televisions, this means that the image is displayed stationary on the screen for a full sixtieth of a second. Then the screen is refreshed and a new image is saved there for another sixtieth of a second. Some TVs have faster refresh rates, and in some countries, image repetition is one-fiftieth of a second apart. The process is the same.

Your Brain on LCD TV Movements

Sixty freeze-frames per second are fast enough to cross the brain's fusion threshold. You do not see any stills, you see flowing movements. However, your brain works fast enough to expect movement during these hold times. The images are stored for so long that your brain assumes that everything in motion remains in motion. But that's not it. It is actually stationary and then jumps to the next position, which is also stationary.

Your brain and your eyes awaiting a gentle movement obliterate the object by moving to follow where it should be. The physiological reasons for this are beyond the scope of this article, but the main aspect is that motion blur is in your head (is not that all?), Which is important when discussing how to get rid of them.

  Smoothing the soap opera effect on a cruise Samsung "data-original =" https://cnet4.cbsistatic.com/img/dfLtPZ7lVp2Wn_bm5tV9Gj8OJCw=/2018/12/05/14d1411e-d4ad-4a6b-9d94-0e1bd7237205 .jpg [19659023] Smoothing the soap opera effect on cruises Samsung

Samsung's name for its motion interpolation technology.


David Katzmaier / CNET

TV manufacturers know the problem of motion blur for years. This is the main reason for higher refresh rates. Modern 4K TVs work at a maximum of 120 Hz but in the 1080p days, there were models up to 240 Hz (or 100 and 200 Hz, depending on which country you live in).

Higher refresh rates are not. Solve the problem of motion blur in and of itself. The pictures are still saved, and if you double the number of still pictures to 60 in 120, you have not really changed anything. You have to change something to and then it will be interesting.

Motion Interpolation

Processing in modern televisions can astonishingly determine what happens between two pictures of video. For example, if a ball is in frame A on the left side of the screen and in frame B on the right side of the screen, the TV can safely assume that the ball in a frame between A and B is the center of the screen.

A 120 Hz television determines what this "AB" frame would look like, then inserts it between frames A and B. This means that more frames are available for switching and less time is "held" for each frame. This is called image or motion interpolation. For video content like sports, a new frame is inserted between each original frame, resulting in less motion blur and more visible detail. However, there is a problem with movies and TV shows with a script.

Almost every movie and non-reality TV show is shot at a frame rate of 24 frames per second. This goes back to the time when almost everything was shot on film. Although the first days had a variety of frame rates, Hollywood opted for 24-hour mode, and that's been the case for decades.

Very few movies or shows are filmed today, but the digital cameras are set to record at 24 frames per second. This is perceived by the vast majority of people as "fiction". Consciously or unconsciously, people set higher frame rates equal to either low-budget or reality shots. News, reality TV, sports, etc. use higher frame rates, usually 30 or 60 fps.

  Smoothing the soap opera effect Vizio "data-original =" https://cnet4.cbsistatic.com/img/-MWr -msBgmJg4_gY8toWPb_RkMo = / 2018/12/05 / 68d85d95-b9e9-4267-93b8-6a7c6342ae69 / 20181205-100713 .jpg

Adjust how much jerk you want to reduce to compensate for motion and blurring.


David Katzmaier / CNET

Interpolating images will increase the apparent frame rate so that 24 fps content will no longer look like [24,500] content as it will not display when viewed on these TVs . is fps content. The interpolation effectively raises the frame rate ($ 1,350 on Amazon) so 24-fps content looks more like 30 or 60 fps. Rather like sports, reality TV or the content that gives this effect its name: the soap opera effect. This is where our friend Tom comes into play.

Many people do not notice or are not interested in the soap opera effect. Others, like Tom and me, can not stand it. The ultrasonic movement not only looks artificial, but can also be distracting and unpleasant. Most Hollywood creators also hate it because that's not what the director intended for his creative vision. If they wanted to shoot at 48 frames per second, they would have shot at 48 frames per second, as Peter Jackson did with the Hobbit .

Fortunately, most televisions not only give you the power to turn them off, they allow you to adjust how intense the frame interpolation is. Instead of a frame made halfway between A and B, it may differ only slightly from A or slightly from B. If your TV has this setting, you should determine if you find a setting that satisfies motion blur reduces that it does not bother you, but is not as intrusive as the more intense frame interpolation modes. Some even separate the processing to reduce the jerking caused by pasting 24fps content onto a 60fps display motion blur. The general term is "Black Frame Insertion", but broadly covers many different ways to achieve a similar effect. In the simplest case, and if the technique gets its name, a black frame is inserted between the real frames.

  bfi-and-refresh-rate "data-original =" https://cnet1.cbsistatic.com/img/g0xJ28LdyLWr9DLIuKYPoM77meA=/2018/05/24/8f02c462-afb9-4419-9862-e931fca655ef/bfi- - refresh-rate.jpg

A simplified representation of the insertion of a black border. The original video would have 60 frames per second of fish. The TV would "insert" 60 black pictures between the real pictures. How long this black image is displayed or if it is completely black is different.


Geoffrey Morrison / CNET

This too has its history in the cinema. Although movies were shot at 24 frames per second, they were not shown at 24 frames per second. This was slow enough that some people saw the flicker. Instead, each film frame was shown twice, with a shutter blocking the light in between. Some cinemas went even further and showed each film frame three times. This blanking was an easy way to get some of the "performance" of a higher frame rate without the cost of adding extra footage.

Inserting a black border lessens sample-and-hold. It pretends better to your brain that there are gentle movements. Unfortunately, there are a few disadvantages again.

When the TV spends half of its time displaying a black screen, its light output goes down. In many cases, this compromise is acceptable because modern televisions are exceptionally bright. In other cases not so much. For example, I have a front projector and the BFI mode can make the picture look very dark.

There may also be visible flicker as the television with the black frame inserted is essentially turned on and off. CNET's television interviews often find that BFI's flicker is too intense to appreciate the improvement in motion blur.

Similar to frame interpolation, black frame insertion has different implementations. Rarely would a TV with BFI mode display a black frame as long as a real frame. It's not necessarily a "frame" either. All LCDs generate light with a backlight . This backlight can also be turned off only for part of the time that the image is displayed on the screen. This is one of the ways that companies can claim that their 60 Hz TVs have a "movement rate" of more than 60 .

Another method is a rolling or scanning backlight that darkens parts of the image in turn. The backlight may darken first in the upper quarter of the screen and then in the middle upper, middle lower and lower quarters. Rinse and repeat.

  Rolling backlight "data-original =" https://cnet2.cbsistatic.com/img/OtO2fNKNqHJoXoZnl-Qx_Iz3fRI=/2019/06/01/42c7c643-1c61-4a60-8d87-5efea217ffa -backlight.jpg [19659051] Rolling Backlight

An example of what a rolling backlight would look like. You will see the picture on the left. Faster than you can see, parts of the backlight are turned off one after the other on the screen. This would be the case for every video image.


Geoffrey Morrison / CNET

There are also stages of how "black" the black frame is. A 120 Hz TV could insert an image that is a duplicate of the previous image, but darker. Not "black", only darker. This method also has advantages and disadvantages. Not so much light is lost, but the movement may not seem quite so keen.

As with frame interpolation, be sure to read and test a TV set with different settings.

Learn more about BFI in Inserting Black Frames: Camera Blur from Oculus to LCD TVs .

The DLP Projector Option

The only two flat screen TV technologies currently available, LCD and OLED, suffer from motion blur. However, there is one more display technology that does not do this: DLP.

Currently only available in front projectors, Digital Light Processing uses millions of tiny mirrors that turn on and off quickly to create an image on a screen. Some movie projectors use this technology . At home, they are not that expensive. You also need a screen, but they are not that expensive either. It's easy to get a 100-inch TV for less than $ 1,000. Many models are even cheaper.

There are, however, several compromises. While modern projectors are very bright compared to older models, they do not detract from the average TV. In a room with dark curtains or if you mostly watch TV at night, this is not a problem. I used a projector as the main TV for over 15 years. However, in this room I use blackout curtains.

  benq-ht2050a-front "data-original =" https://cnet3.cbsistatic.com/img/oStJca-pdb4qDannZivcxPOs_nw=2019/06/01/98767550-c0ce-4741-acbf-791597b3337c/benq-ht2050a -front.jpg

Many inexpensive projectors use DLP technology that does not suffer from motion blur.


BenQ

The other aspect is the overall picture quality. The better pictures of DLP projectors look good and are exceptionally sharp, especially when moving in comparison to other display technologies. However, they do not have the color depth or contrast ratios of other technologies. The picture does not "pop" like it does on an OLED TV. HDR is basically just in the name . It can read the HDR data, but since they are not bright and the contrast ratio is poor, it will not look much different from non-HDR content.

If you hate motion blur, this is certainly the best option. I'm a projector proselytizer, but it's definitely a lifestyle choice. You really need to hate motion blur to find the reason for the change. Do you know the motion control of your TV? Many new televisions, especially mid and high end models, have some of these adjustment options when dealing with motion blur. If you are disturbed by motion blur, hopefully you can find a setting that is right for you, without disturbing the rest of the family.

I have long hated motion blurs, which are much more conscious and annoying than my colleagues. Since I also hate the soap opera effect, the only current option for reducing motion blur on my current projector is to insert a black frame. And after a few months … I switched off. The compromise between a darker image and a flicker that was just perceptible was no longer worth the better-known detail.

I'm not telling you to just give up, blur fellow hate. If you have had your TV for a while and can not overcome motion blur, try the various settings above. If you have received a new TV that may have been upgraded from an old plasma or DLP rear-projection TV, check if any of the settings work. If not, take some time and try to get used to it. Hopefully you will.


Do you have a question for Geoff? First, read all the other articles he has written on topics such as why you should not buy expensive HDMI cables TV Resolutions Explained How HDR Works and more.

have a question? Tweet him at @TechWriterGeoff then check out his travel photography on Instagram. He also thinks you should look at his best-selling science fiction novel and its sequel.


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