Misguided or misunderstood 60hz? 120hz? Samsung purchase?

cwa

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Sep 18, 2017
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I spent a couple hours at Best Buy choosing a smart tv to my specs, (4k, smart tv, 120hz, at least 4hdmi ports, optical digital audio, tv tuner, at least 45”, around $500-$600). The main feature I requested was 120hz REFRESH RATE. After much research I listed this as a top priority requirement. I discovered this is a rating that many tv makers deceive customers by using different words than REFRESH RATE (motion rate, tru motion, effective refresh rate, etc.) and then put a higher number with those words to trick the customer into thinking it is a higher refresh rate. I ultimately splurged to buy the $900 Samsung UN49MU8000FXZA after being reassured this tv has a 120hz REFRESH RATE. However, after making the purchase (but not getting the tv because it is currently out of stock) and looking on the internet, most web cites say this is a 60hz REFRESH RATE but is called MOTION RATE 120.
What is the REFRESH RATE of the Samsung UN49MU8000FXZA?
We mainly use our tv for watching regular cable broadcast movies, baseball games, and football games. Does the quality of this Samsung measure up to a 120hztv? Is there a better quality tv for less than $900?
Thanks
 

That's actually an improvement over how these TVs used to be marketed. They used to just be called 120 Hz. At least now they're distinguishing what's really going on.

120 Hz TVs do not let you feed it a 120 Hz video signal (even if you could, you'd need a Displayport input to accomplish it - can't do it over HDMI). Their 120 Hz refresh rate is for one purpose and one purpose only - eliminating judder when playing 24 fps movies.

A lot of movies on film were shot at 24 fps. When you try to play these on a 60 Hz TV, well, 60/24 = 2.5. That's not an integer. You're forced to show frame 1 for 2 TV frames, frame 2 for 3 TV frames, frame 3 for 2 TV frames, frame 4 for 3 TV frames, etc. This uneven frame duration (called a 3:2 pulldown) causes a subtle jerky motion called judder. There are two technical solutions to eliminating judder.

http://www.hdhead.com/illustrations/pulldown.gif

First is frame interpolation. A computer analyzes the video and makes up intermediate frames between the 24 movie frames every second. It synthesizes 60 fps video, and plays that back at 60 Hz. Unfortunately this creates what's commonly referred to as the soap opera effect. It no longer looks like a movie, it looks like a video. Many people don't mind this, but the people who do absolutely hate it and are very vocal in their complaints about it.

The second method is to use a screen with a 120 Hz refresh rate. The TV's electronics only accept a 60 Hz (or 30 Hz or 24 Hz) input. But if it sees the input is 24 Hz, it switches to a 120 Hz refresh rate. 120/24 = 5, an integer. So to show a 24 fps movie, it simply shows 1 movie frame every 5 TV frames. No more judder.

There is no way to plug in a computer and drive the screen at 120 Hz. The 120 Hz capability is only used to eliminate judder in 24 fps movies. So when these TVs were initially advertised as 120 Hz, it was a bit deceptive. If they're now advertising them as 60 Hz, with a 120 Hz motion rate, that's actually an improvement. (240 Hz TVs are the same thing, except for 3D video. A 3D TV rapidly flickers between the left and right images, so a 24 Hz 3D movie has 48 frames per second. And you need 240 Hz to eliminate judder.)

Just to reiterate: HDMi does not (yet) support a 120 Hz signal (well, 3D HDMI does, but AFAIK there's no way to use that with a non-3D signal). If there was a TV which let you feed it a 120 Hz video signal, it would have Displayport input, or maybe DVI dual-link.
 

cwa

Prominent
Sep 18, 2017
3
0
510
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I'm pretty upset about being told by best buy it's 120 refresh rate and am thinking about 1. as a matter of principle, cancelling the order and going to Walmart where I can get the same tv 2 days sooner or 2. I would like to know if there is another tv <=$900 with as good or better picture quality? Is there? And still meet my other requirements? That's the real question.
 

That's actually an improvement over how these TVs used to be marketed. They used to just be called 120 Hz. At least now they're distinguishing what's really going on.

120 Hz TVs do not let you feed it a 120 Hz video signal (even if you could, you'd need a Displayport input to accomplish it - can't do it over HDMI). Their 120 Hz refresh rate is for one purpose and one purpose only - eliminating judder when playing 24 fps movies.

A lot of movies on film were shot at 24 fps. When you try to play these on a 60 Hz TV, well, 60/24 = 2.5. That's not an integer. You're forced to show frame 1 for 2 TV frames, frame 2 for 3 TV frames, frame 3 for 2 TV frames, frame 4 for 3 TV frames, etc. This uneven frame duration (called a 3:2 pulldown) causes a subtle jerky motion called judder. There are two technical solutions to eliminating judder.

http://www.hdhead.com/illustrations/pulldown.gif

First is frame interpolation. A computer analyzes the video and makes up intermediate frames between the 24 movie frames every second. It synthesizes 60 fps video, and plays that back at 60 Hz. Unfortunately this creates what's commonly referred to as the soap opera effect. It no longer looks like a movie, it looks like a video. Many people don't mind this, but the people who do absolutely hate it and are very vocal in their complaints about it.

The second method is to use a screen with a 120 Hz refresh rate. The TV's electronics only accept a 60 Hz (or 30 Hz or 24 Hz) input. But if it sees the input is 24 Hz, it switches to a 120 Hz refresh rate. 120/24 = 5, an integer. So to show a 24 fps movie, it simply shows 1 movie frame every 5 TV frames. No more judder.

There is no way to plug in a computer and drive the screen at 120 Hz. The 120 Hz capability is only used to eliminate judder in 24 fps movies. So when these TVs were initially advertised as 120 Hz, it was a bit deceptive. If they're now advertising them as 60 Hz, with a 120 Hz motion rate, that's actually an improvement. (240 Hz TVs are the same thing, except for 3D video. A 3D TV rapidly flickers between the left and right images, so a 24 Hz 3D movie has 48 frames per second. And you need 240 Hz to eliminate judder.)

Just to reiterate: HDMi does not (yet) support a 120 Hz signal (well, 3D HDMI does, but AFAIK there's no way to use that with a non-3D signal). If there was a TV which let you feed it a 120 Hz video signal, it would have Displayport input, or maybe DVI dual-link.
 
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