Hi. Is there any real difference between 60 herts and 120 hertz on the new tvs?
I saved over 1000 on my aquos LC46D62U by getting the regular model (which i assume is 60 hertz, or else they would advertise 120).
And when I say difference, I mean to our eyes, (not just on paper ;) )

When I watch hockey in HD, it looks super crisp to me. I mean I can't complain. I have a 46inch tv and I sit about 10-11 feet away.

When I watch SD though, thats different, the closer I sit, the more I notice pixelization during fast moving pictures. Would more hertz give SD a better picture? Or would it not matter?
Please reply, thanks!

Quote:
A Television with a 60hz refresh rate represents complete reconstruction of the screen image 60 times every second. As a result, this also means that each video frame (in a 30 frame per second signal) is repeated twice every 60th of a second.

If you have a TV with a 120hz refresh rate that is 1080p/24 compatible (1920 pixels across the screen vs 1080 pixels down the screen, with a 24 frame per second rate). The TV ends up displaying 24 separate frames every second, but repeats each frame according to the refresh rate of the TV. In the case of 120hz each frame would be displayed 5 times within each 24th of a second.

The whole thing boils down to the concept of separate frames vs repeated frames. In the case of frame rate vs refresh rate calculations, repeated frames are not considered separate frames as the information in the repeated frames is all identical. It is when you move to a frame with different information that you have to count it as a new frame.

You can find more info here: hometheater.about.com/od/televisionbasics/qt/framevsrefresh.htm

The issue is with displaying film-based material on progressive (digital) displays. A display operating at 60 Hz refreshes its image 60 times per second (i.e. it can display 60 unique images per second). 120 Hz is obviously double that. Here's why that is significant.

Film is shot using 24 frames per second whereas video is shot using 30 or 60 frames per second. For the video it's no problem displaying this smoothly on a display that operates at 60 Hz because the number of video frames divide evenly into the display's refresh rate. e.g. If the video you're displaying has 30 frames per second you simply display each frame twice. However, if your source is film with 24 frames per second you can't directly map the film frames to the display frames. To get around this they use a technique called 3:2 pulldown. In a nutshell, 3:2 pulldown is an algorithm that displays some of the frames 3 times and some of them twice in order to map the film's 24 fps to 30 fps. The downside of 3:2 pulldown is it introduces motion artifacts. This is mostly noticeable in fast moving scenes or pans - you may see blurriness, choppiness, etc.

This is where 120 Hz refresh rates come in. 120 Hz is nice because 24 fps film or 30 or 60 fps video all divide evenly into the refresh rate of the display so you no longer need to use 3:2 pulldown. There's a good article here that goes into a lot more detail about 3:2 pulldown: http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

To answer your specific questions, HD hockey looks great and smooth because it's shot in video so no need to do any 3:2 pulldown. There shouldn't be any difference between a 60 Hz display and a 120 Hz display for video sources (assuming all other components of the display are equal). It won't make any difference for SD either. SD looks like crap because it's SD, plain and simple. :) The difference would be with film based material. If you have a film based source and a Blu-ray or HD DVD player capable of outputting 1080p/24 then you will get an optimal picture with a 1080p/24 display running at 120 Hz because it won't need to do any 3:2 pulldown.

http://www.digitalhome.ca/forum/showthread.php?t=17869

Thanks so much Grog for your reply.
Now I'm reassured that I made the right decision at the time to purchase my tv (especially now that it went up $300 in price for the same model :-D
I don't plan on getting hd dvd's or blue ray discs, even if I had a high end player. Just not my thing (I burn all my movies off movie central, etc, for personal use).

If you don't see the difference, keep what you have.

To me, fast action looks really bad and not smooth on LCD at 60Hz. 120Hz is a bit better, but I hate the pixelation effect so I went with a plasma. (same for my projector, I went with a DLP because I could not stand the screen door effect)

If everything else about the display is equal there's no reason that 120 Hz should look any different than 60 Hz for video-based content. You aren't displaying any more information with a 120 Hz refresh rate. At best the source content will be have 60 frames per second so you just display the exact same frame twice if displaying on a 120 Hz display.

However, odds are everything else isn't equal with with a 120 Hz display vs a 60 Hz display. The 120 Hz display will likely have a higher quality panel with a better response time. Response time is how quickly a pixel can "change" from one colour to another. In older LCDs this response time was in the 20-30 ms range so fast moving scenes would be particularly bad because the pixels couldn't even keep up with the refresh rate (at 60 Hz the frame is being redrawn every ~16 ms). Newer displays are much better with response times of just a few milliseconds but it can still be perceptible.

Bottom line - you may very well see a difference in quality between a 60 Hz and a 120 Hz display for video-based material but that difference isn't because of the refresh rate. It's because of differences in panel quality or perhaps other components of the display, just like two displays with the same refresh rate can have very big differences in quality.

I thought I read somewhere that 120 Hz LCDs do an averaging for the extra frames. That would make motion look smoother.

That's right Otown, well I know it is for Sharp 120 hz tvs. The processor and chipset has an algorithm that decides what those extra frames could look like if there was some motion there making it seem smoother when watching it.

I stand corrected then. :)

My gut feel is the greater benefit will be for 24 fps film material but it sounds like there can be some improvement for 30/60 fps video as well. As with any of this stuff though the only way to really know for sure is to view it for yourself. Some people aren't bothered at all by various video artifacts whereas others are hyper sensitive to them. As mart242 said, if it looks fine to you that's all that really matters in the end.

Today most professional level “video” cameras and decks are also capable of shooting true 24FPS (frames per second.) The problem is, when broadcast, it’s converted to 29.97fps 60 hertz interlaced. Films converted to broadcast are also converted to 60i using the 3:2 pull down mentioned in an earlier post.

As for the motion artefacts you’re seeing, this is usually caused by a lossy mpeg2 long GoP codec and has very little to do with the signal being 60i.

Long GoP stands for a long group of frames. The I-Frame will have the full resolution but the frames between the I-Frame can only predict the missing data thus the more motion (pixels changing very fast) the more artefacts you see. A 1080i cable signal probably has no more then two I-frames per second. That’s only two full resolutions frames from every 30 frames per second 60 hertz interlaced video.

This is the exact issue I'm trying to figure out. My post from the AVS forum:

---

I have been trying to get a better understanding of this 2-3 pulldown issue and have read a few articles and posts that discuss it. The reason I'm looking into it is because I'm looking to buy a new TV and I was looking at the Sony SXRD KDS-60A2020. Having seen it in the store, the display looks great but it still suffers from the "judder" during pans and other motion sequences. I guess my confusion comes from where the real problem is.

I see that some display devices can accept a 1080p24 signal, but how does that help? Doesn't that display still need to somehow convert the 24fps signal into 60fps? Isn't that where the problem comes in? I don't see why it makes a difference if the display does it or if the DVD player does it, or something else does it. From what I can tell, the source needs to be converted *somewhere* along the way.

I see that the new Sony SXRD TVs are supposed to have the 24fps input and 120Hz display, correct? If so, does that eliminate the whole 2-3 pulldown issue? I know that 120 divides evenly by 24 which means there is no weird adding/removing frames.

In the end, I'm trying to decide if it's worth waiting for one of the new SXRD models or not. This seems to be a big improvement in quality since I really notice the judder and would love to get a TV that is not affected.

The other question is will you need a DVD player capable of sending the TV 24fps? I have an HD-A2 and don't want to replace it if I don't have to.

Thanks for the help

60 isn't evenly divisible by 24 thus 3:2 pulldown. Since you can't evenly distribute the 24 frames over 60 cycles you get judder.

Some TVs do 3:2 pulldown better than others mind you.

120 is evenly divisible by 24 so you can do a 5:5. Every 5 cycles display another frame. Not all 120hz televisions actually accept 1080p/24fps so be careful.

Another way to achieve smooth panning is making a display that can do 72hz like the Pio plasmas. They do 3:3.

From what I understand the Sharp aquos aren't true 120hz sets. They are essentially 60hz sets with a black frame inserted between every frame. So instead of having each frame showing on the screen for 16.6ms they are shown for 8ms and then 8ms for a black frame. This apparently tricks your eyes to see smoother motion because each frame on the screen for less time.

I could be wrong, but I believe there are 2 models of Sharp Aquos (that is relevent to this post)
1 is 60 herts, teh other 120 herts.
if you go on futureshop.ca you can see the two
Mine is the 60 hertz version, and for a $1000 more you can get teh 120 hertz.

Yes the D62U are 60hz and the D82U and D92U are 120hz

From what I understand the Sharp aquos aren't true 120hz sets. They are essentially 60hz sets with a black frame inserted between every frame. So instead of having each frame showing on the screen for 16.6ms they are shown for 8ms and then 8ms for a black frame. This apparently tricks your eyes to see smoother motion because each frame on the screen for less time.
Could we get a reference please....

Could we get a reference please....

I knew I should have kept a mental note. I read it in a HT magazine when I was in Chapters. I might go and try to find out this weekend.

I am interested in the sharp aquos LC46D82U, because it looks awsome and thought that the 120hz was better for fast action like sports.

The title of this thread is 60hz vs 120hz refresh rates, but the specs on the sharp aquos LC46D82U talk about 120hz frame rate conversion.

So my question is what is the difference between refresh rate VS frame rate conversion?

Also if anybody has purchased the sharp aquos LC46D82U let me know your feedback.

I can't seem to find the article that talks about Sharp's 120hz conversion but it's not true 120hz. I have the aquos 46d82u and I like it a lot. For fast motion it is definitely better than the d62u but I don't find it to be a huge difference. It just makes me feel better that it has 120hz conversion even though apparently it's not true 120hz which would be awesome.

In Cnet's review they talk about that D82 model (I think it was that one) being 120hz, but that they were then disappointed to learn it wasn't true 120hz, but a frame rate conversion.

Have to admit I don't have a clue what that means, I assumed it was due to some kind of software trickery.