Big difference between 120Hz Vs. 60Hz?

Question

I am looking to purchase a HD LCD TV in the next couple weeks and was wondering if there was a huge difference here. I walked into Best Buy tonight to compare the two and to see if there is a point paying an extra $1000 for the 120Hz. I noticed that the 120Hz TV's looked somewhat "fake" while watching the camera movement. Anyones thoughts?

Answer 1

Here's the thing... technically speaking, it makes no sense to have a 120Hz refresh rate over 60Hz because there is no new additional information on the screen; each frame is simply drawn twice rather than the original frame persisting until the next frame is due up.

Having said that, TV manufacturers employ some trickery to fool your eyes and brain into perceiving smoother motion. Isn't that the whole idea with TV anyway, to trick our minds? Often times a black frame will be inserted between every other frame or some sort of interpolation will take place (using two reference frames to generate an additional frame with new information). Different methods yield slightly different results but the intention is the same.

Bottom line, trust your eyes and not the marketing specs. Choose a screen that you and your wallet can be happy with. Manufacturers will slap on any spec that they believe consumers will swallow, especially if that spec is in the form of a number that gets higher and higher... because of course, more is better right?

Answer 2

120Hz definitely smooths out slow to moderate motion on the screen.  At CES I saw numerous side-by-side demonstrations of 60Hz vs 120Hz and the difference is dramatic.  It does not add any artifact or pixellation to moving objects--that comes from excessive compression at the source.  In addition, since 120Hz is an exact multiple (5x) the movie frame rate of 24Hz, each movie frame can generate the same number (5) of TV frames; for 60Hz sets, half the frames generate 2 60Hz frames and the other half make 3 60Hz frames (alternating).  This produces an unevennes of motion from movie sources (called "judder") which the 120Hz sets can eliminate.

With inter-frame interpolation, the smoothness of motion in movies seen on a 120Hz TV is better than you get in a movie theater.

Answer 3

The biggest impact 120 Hz has on an LCD TV screen is the elimination of motion blur. All 120 Hz machines do a very good job at removing this artifact. NO 120 Hz machine is capable of removing motion blur. You will need 240 Hz before you see much impact on this artifact. Also, 120 Hz machines can and are overwhelmed by panning shots with motion. They produce pixelization artifacts and can cause artificial movements as you have seen in your own evaluations. Jitter is, in my opinion, the most annoying artifact of an LCD TV and is worthy of removal, but I have a very hard time justifying the cost of these features with their inability to remove all LCD deficiencies without producing additional artifacts.

Additional Details:

Fact - 120 Hz uses an additional co-processor to interpret the signaled frames and calculate the intermediate position of moving objects. It is this information that is used to create the additional 60 frames per second.

Fact - LCD TVs do not insert black frames. Instead they use a technique called sample & hold. They maintain their images on screen until the next frame is displayed. This is the root cause of motion blur and jitter.

Fact: Side-by-side demonstrations at CES are manipulated to show the viewer just what the manufacturer wants the viewer to see. I've seen these demos & they would have you believe that 120 Hz is perfect.

Fact: 120 Hz co-processors can be overwhelmed. When this occurs, they can not complete their video processing. They must stop, present the image as it currently exist and start the processing of the next interpreted frame. When this happens they DO create pixelization artifacts. You do not have to believe me, just do your own testing. The best platform to demonstrate this is the exalted SONY KDL-xxXBR4 and the movie "Happy Feet". Set the XBR's video motion compensation to "High" and play chapter 12 of "Happy Feet". Now just watch the right side of the screen as the mountains pan past the screen for the pixelization. Next watch the heads of the 5 amigos as the panning shot shows the mountains moving behind them. Watch the side of mumble’s body as the mountains move past in the background. Also watch his flippers as he dances. All of these edges pixelate. These artifacts are produced throughout the movie. These artifacts have nothing to do with the production of the movie or excessive compression at the source; they are not present with the TV's video motion compensation turned off and can only be prodcued by the TV's own 120 Hz co-processor.

With inter-frame interpolation, the smoothness of motion in movies seen on a 120Hz TV is much worse than that you get in a movie theater.