Motion on TVs: Black Frame Insertion and PWM dimming (2/5) –
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Motion on TVs: Black Frame Insertion and PWM dimming (2/5) –

September 10, 2019

Hi, I’m Cedric from This video is part of a series about Motion
and today’s subject is flickering, either via Black Frame Insertion or PWM dimming.
And we are going to talk about how does these things affect motion blur. First we will look
at it from a theory standpoint, and then we’re going to test some TVs to see how it is in
real life. In the previous video, we saw that when we
follow a moving object with our eyes, it results in a blur due to the frame rate. This is assuming
the frame is displayed for the whole duration. Or in other words, that the screen is using
a sample-and-hold method liked OLED TVs. But this is not true for all screens. Some
of them flickers, which reduces the perceived motion blur. Here is a demonstration of a
screen that displays a frame for a very short time. It the field of view of the moving eye,
you can see that the logo is quite clear since it always appears at the same spot, so you
don’t have the blur caused by the shift of the movement. This technique is called
Black Frame Insertion since it is like if you inserted a black frame in between each
frames. Now let’s talk about a real-life example
of a Black Frame Insertion. I am going to use the Sony X750D for this in our test room.
By default, it doesn’t flicker at all. So if I take a picture. It looks like what you
would expect. Now let’s turn on the ‘Clearness’ feature,
which is the Black Frame Insertion. You can see that the screen starts to flicker
and if we take a picture. It looks a lot more clear now. It is slightly blurry though, that’s
because the TV still needs to display the frame for a little bit in order for us to
see a picture. You will notice though that the overall screen brightness is a lot darker,
that’s because the backlight is turned off most of the time. Also, the constant flickering
can be bothering for some people and cause headaches.
We can even see even more what the backlight does by looking at the oscilloscope. You can
see that it flickers at a frequency of about 60Hz and that the pulse last about 2ms.
Now let’s look at an example of a different kind of flickering: PWM dimming. PWM stands
for Pulse Width Modulation, which is a way to control the power by flickering the voltage
instead of simply reducing it. That Sony TV doesn’t use PWM Diming, so if I reduce the
backlight. You can see that it simply reduces the light instead of flickering.
Let’s try this on a Samsung TV KS8000 which uses the PWM dimming. At max backlight, you
can see that it doesn’t flicker. But if I reduce the backlight, it starts to flicker,
but not as much as the Black Frame Insertion. The frequency in this case is 120Hz which
is twice as fast as a real Black Frame Insertion at 60Hz. The bad thing about it is like Black
Frame Insertion, it can give you a little bit of a headache. But the good thing is that
it helps clarify the movement a little bit. Let’s take a picture to see how it looks
like. What is interesting here is you can see a duplication of the logo. That’s because
the frequency of the PWM dimming is 120Hz, so each frame is displayed twice. Back to
our illustration of a Black Frame Insertion. In the case of a PWM Dimming at 120Hz. When
the content is 60 frames per second content, each frame will flicker twice. In your field
of view of your moving eye, that means the logo will appear twice per frame, but at a
different position, which is what creates the duplication of the logo. So you will see
a duplication each time the frame rate of the content doesn’t match the flickering
of the TV. So overall, a flickering of the screen can
reduce the perceived motion blur when following a moving object. But it comes at the cost
of a dimmer screen and it can be tiring for the eye. In our reviews, a perfect TV is a
TV that doesn’t flicker at all by default, but that has the options to add the flickering
if the user wants it. If you want to check out all our measurements
of which TV flickers and at which frequency, on the link in the description below. If you
like this video, subscribe to our channel, and see you next time time!

Only registered users can comment.

  1. I can't live without black frame insertion on my displays. I prefer it even over HDR. It's impossible for me to play video games without it. Even OLEDs are too blurry for me. Had an LG C6 Oled, and I much prefer the Vizio P65 with clear action on.

    I come from owning plasma TVs for many years, which is why the flickering doesn't bother me, and why I can't stand typical lcd blur without backlight strobing.

  2. Flicker destroys my eyes for whatever reason, yet I have perfect vision according to the optomitrist. I love the clarity of these kinds of methods but it's just so uncomfortable! In the end I end up being used to frame interpolation on a low setting to fake a higher frame rate and way less judder (especially in 30fps games) . Does the job, somewhat

  3. Just wanted to say the work you do is amazing, one of the best review and education services for technology i've ever seen. Thanks for what you do for us Plebs.

  4. great video! I have the lg C6p and love it. However, without deblur turned up to 10 and real cinema setting on, I get noticeable blurring and judder when the camera pans left to right or vise versa. Coming from a plasma, I am used to crystal clear images even with camera pans and way less judder as well. The only remedy for this is to turn the dejudder setting up or set it to "clear." What's weird though is some sources look great with just deblur set to 10 and other similar sources look terrible and require the clear setting which looks like a soap opera. After watching your video, I suspect lg needs to improve their PWM or eventually allow BFI to solve the urge and judder issues. Still though, the images on this OLED are light years better then my old Samsung plasma. Just wish the motion was similar to the plasma tech.

  5. Yeah I think I'll save my money wait for an OLED with BFI. Would be a sweet feature for video games at least.

    Awesome website, by the way. Learned a lot about TVs from it.

  6. does samsung''s Clear Motion Plus work the same as in the sony's.

  7. Does Game Mode (KS8000) use BFI or PWM?
    Also when the backlight is lowered, what level until the flicker appears (i can see at about 15 its still a solid reading)

  8. I was just doing some channel surfing the other day and I came across your channel, these Motion Videos are awesome and very professionally done.
    I've never found anywhere as informative as you on the subject of motion, related to T.V's and Monitors, Congrats and Thank you…(Subbed)

  9. Just a side note, if you take a video of the screen with your mobile capturing at 60FPS video, you will see the pwm at backlight level 13 down to 1.
    Level 14 and up has no noticeable sign to the camera.
    I will upload a video of my findings. (ignore my voice, i was experimenting trying to find the flickering).

  10. Whats up Cedric, but i have a Samsung 2014 40" H6350 TS01 Tv and i want to know if its got PWM or Black frame insertion, as i hate the trail that fast moving images leave behind LCDs. And if so, how do i activate it? I am currently running it on PC mode, also is 50 sharpness neutral on PC mode or 0?

    Also, whats better, PWM or BFI? From this i would assume PWM is.

  11. User-adjustable black frame duration is what we need. And even some controls to control the shape of the waveform: square, sine, saw etc. Sine wave will give a more gentle fade to black, less flicker. Saw wave could be a bit more flickery; square wave will be most flickery. Allow the user to choose what works for them.

  12. judder is when you crank up the motion plus up it rips the picture in half in small skinny things like sticks and 24p content will tear at the tops and bottom with here and there with fast moving things, watch 60 fps content or more for judder free viewing

  13. Question. Somehow OLED on laptops all flicker PWM at 240hz. Do the LG C7 / Sony A1 have any flickering? I know your reviews on your sites doesn't say these tv's don't but I am just double checkinf

  14. Cedric you are the man. Your explanations are as clear as day. I emailed you guys a few weeks back about 10bit vs 8bit+ FRC . You answered me that there is no piece of gear that you can use to pinpoint if a panel uses FRC. I hope you find out a method to prove FRC. Do you guys have a video on FRC vs 10bit? I am going to search for it. Keep up the amazing and clear work!

  15. 4:45 and it explained more than I came here for in less time than other channels would have needed to explain BFI alone I guess…

    Excellent channel, subscribed!

  16. So PWM is represented in the graph by the line bottoming out? I’m curious because the X810 review has a perfect line, but the X850E does dip a bit…but doesn’t bottom out.

  17. man you have to look for a speech therapist, the way you speak R is horrible. it can be aceptable in your country but its weird for general english speakers

  18. Very nice video. I have a question about NU8000 which supports BFI in game mode. If you use it while playing an HDR game wouldn't the dimming spoil the HDR experience overall? It's kinda like a paradox,i can't really understand if we are supposed to use it or not while playing HDR games.

  19. Why is the PWM frequency so low? Most switching power supplies used PWM of 10kHz and more, so why cant the LED backlight be controlled by PWM in higher frequency than hundred Hertz range?

  20. if the content is 60hz, and the PWM is at 120hz, why the logo appears twice at different positions? is it supposed to appear twice at the same position? the content is 60hz so why is there an extra picture showing the logo in a different position?

  21. Discover the Sony x750f motionflow clearness set 1 and it perform without Flickering! Even it ips panel native contrast low perform.. But function BFI pair with x750f surprise with 10/10 score ^_^

  22. "If the user wants it." Perfectly said. I know a lot of people don't like the smooth motion effects and that's fine. I for one love the "soap opera" effect when watching movies so I appreciate that television manufactures have given a variety of ways for me to experience that. As long as they include an option to turn those effects on and off we, the consumers, can be happy. It'd be nice if they included more information on how to do that and what's going on behind the scenes but I guess that's what YouTube is for?

  23. I own a BFI monitor and you know something it makes me sad, very sad, sad to think cgi artists working on game never ever see how their work really looks because without BFI you don't, all you see is a blurry mess, BFI is the ultimate mode of viewing you see textures and text as sharp as a still picture in movement !!! I really hope the 2019 LG oleds have a properly working BFI and that this will become an industry standard once they manage to make it work properly because all the monitors I tested that had BFI it didn't work :/ the ones that work (as usual you could say) are "hacks" not commercial products, hacks of the 3D mode of old pc monitors where they used the flickering used for the 3D to insert black frames instead more here

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