School me on 60 / 120 hz

[jemrey81]

I was helping a buddy out tonight installing some home theater stuff, and notice that when the tv came on it said 60 hz at the top..... it's a 120 hz tv. I couldn't find any settings for this. Any ideas? I had the Avatar dvd in the blu ray player (the player needs an update to run the Avatar blu ray) for testing and it showed up at 60.

Does the tv decide to run at either 60 or 120 depending on it's input?

For background, it's a new samsung 46" unknown model right now. He has a new samsung blu ray player unknown model right now (it's the new one that is built in wifi), a new tivo, and a denon receiver. All equipment is new. I have the tivo and blu ray going into the receiver via hdmi and then out of the receiver into the tv via hdmi. All cables are new and from monoprice.

[Fongolio]

To use the 120Hz feature I believe Samsung calls it Auto Motion Plus. Look for it in the menu. 120Hz is also required for 3D display and may automatically switch if a 3D movies is detected. The best advice....read the manual.

[mystik610]

Without getting too technical, the images we see on a TV are actually a series of flashing images with black frames in between. A 60hz tv will flash 60 images a second.

So what you see as a continual image is actually:

1st frame - black frame - 2nd frame - black frame - 3rd frame

There are no real 120hz input signals outside of PC's...Most US video is 60hz. A screen with a 120hz refresh rate will display 60hz content by repeating frames (60 frames x 2 = 120)

Given that most US video is 60hz/60fps, a 120hz doesn't do much for most material...but it goes a long way with film/movies. Film/movies are shot at 24fps...the juddering that we have grown accustomed to with film is caused by an un-even distribution of frames when displayed at 60fps, on a 60hz display (24 doesn't evenly divide into 60). With Blu-ray we're seeing film being brought over at 24fps....this is where a 120hz display really benefits. 76hz, 120hz, and 240hz displays are able to rectify juddering by evenly displaying frames, as 24 will divide evenly into 76, 120, and 240. A 120hz display will flash each frame 5 times per second (120 / 24 = 5). For a lot of people, movies look odd on 120hz displays because they have grown accustomed to the juddering that makes film look like film.

I think what most people attribute to the PQ of a 120hz screen, however, has less to do with the refresh rate, and more to do with the frame interpolation image processing (auto-motion plus, motion flow, etc etc)

LCD's suffer from motion blur because the pixels in the LCD panel don't move quickly enough to produce the black frames as they should. It takes too much time for the pixels to move back and forth from a frame to a black frame. To rectify this, TV manufacturers intoduced frame interpolating technology, which will predict what a hypothetical frame between two frames would look like. To smooth out the picture, the interpolated frames are displayed instead of the black frames..so it would look a little more like:

1st frame - interpolated 1.5 frame - 2nd frame - interpolated 2.5 frame - 3rd frame.

Some people like how this looks...to others it looks very artificial and computer generated...beacause the image is being processed, and is literally artificialy and computer generated.

It should be noted, that a 120hz display will still refresh at 120hz even if the frame interpolation modes (ie auto-motion plus) are turned off.

[Zeros]

That was very informative Mystik, thank you.

[anhchungdoan]

Don't know if this will help or not but take it or leave it as you wish.

A camera rolls at 24FPS and a flat panel will display at 8 Mil second response that will give you 60HZ. Some flat panel TVs have a processor to speed up the response time to 120hz/ 4 Mil second RPT for action and fast moving replay scenes. The faster response time will smooth out the " motion blur". Some LCD flat panels have a 240 Hz/ 2 Mil second RPT processor that enhance futher the moition blur.

Most Tvs will give you the option to turn on or turn off the " Motion flow" feature. The "motion flow" processor designs for fast motion playback such as sports, racing cars, football games....other than that in a normal movies, it ain't enhance nothing.

[DaveHCYJ]

You should also note that all this 60 vs 120 vs 240 display rate stuff only applies to LCD type flat panels. Plasma flat panels are effectively immune to this problem (they have their own different types of problems).

Also, the 60Hz your TV displayed may have just been the input signal, rather than your TV's refresh rate. Most input signals today are either 24 or 60 Hz, my TV and receiver will show this "input statistic" information.

[mystik610]

You should also note that all this 60 vs 120 vs 240 display rate stuff only applies to LCD type flat panels. Plasma flat panels are effectively immune to this problem (they have their own different types of problems).

Also, the 60Hz your TV displayed may have just been the input signal, rather than your TV's refresh rate. Most input signals today are either 24 or 60 Hz, my TV and receiver will show this "input statistic" information.

Plasmas don't suffer from motion blur, but a 60hz plasma will still judder when playing 24p material. This is why you see 76hz 480hz 600hz sub-field drive plasmas.

[Analog Kid]

Plasmas don't suffer from motion blur, but a 60hz plasma will still judder when playing 24p material. This is why you see 76hz 480hz 600hz sub-field drive plasmas.

My Panny plasma offers a setting for 24p material that allows me to view at 48Hz. The other setting will change the 24p signal back to 60Hz. Are there any advantages to using the 48Hz setting as long as the Blu-Ray player is set to output the 24p signal?

[mystik610]

My Panny plasma offers a setting for 24p material that allows me to view at 48Hz. The other setting will change the 24p signal back to 60Hz. Are there any advantages to using the 48Hz setting as long as the Blu-Ray player is set to output the 24p signal?

You're going to want to use the 48hz setting anytime you're viewing 24p material...this will eliminate juddering and smooth out the image.

[Analog Kid]

You're going to want to use the 48hz setting anytime you're viewing 24p material...this will eliminate juddering and smooth out the image.

I had done some experimenting with this setting and did notice that motion seems more "real" on the 48Hz setting. Even the wife noticed the difference.

[Conradicles]

In a movie theater, what do we see? Just curious.

[mystik610]

I had done some experimenting with this setting and did notice that motion seems more "real" on the 48Hz setting. Even the wife noticed the difference.

That's because the frames are being displayed evenly, creating more life-like motion in movies.

A lot of people actually don't like the effect, as we've grown accustomed to the juddering in film content, and have accepted that as a distinct characteristic of film. People think that it makes film look like a home video or soap opera...and it does, because home videos and soap operas are shot at 30 fps, and display evenly on a 60hz display.

These pull-down methods (2:2 pull-down in your case) rectify problems that have long existed in converting film to video. It might look odd to some, but this is the way film was intended to be displayed.

[mystik610]

In a movie theater, what do we see? Just curious.

24 frames per second

[anhchungdoan]

+1.

24 FPs as intended by director . When tranfering from 24 FPS from films to TVs broadcast, method of 2:3 or can be referred to as 3:2 pull-down is used to transfering 24FPS to 29.97 FPS . The 3:2 pull down method is used on North America.

Some PAL films use 24FPS when being transfered to TV broadcast with 2:2 pull-down method to produce 25FPS so there is not much a big deal.