I'm hoping that someone here can give me the straight answer on this one. I've been reading various forums but the answers are a bit sketchy. From reading many posts here I'm more inclined to believe guys here.

Here is what I've managed to piece together. If I've got any of it wrong I'd appreciate being corrected.

The primary goal of 120Hz displays is to eliminate judder (jumpy looking movement at the edges) when displaying film originating material (24fps) especially noticeable on slow horizontal pans (hence the brick wall demo in many stores).

With 60Hz displays such material is shown for different length of time: Every odd frame - twice, every even frame - 3 times (12*2+12*3=60). Hence, 3-2 pull down.

A 120HZ display shows every frame 5 times (5*24=120)so there is no judder.

However, it appears that there is no difference in presenting 60Hz footage (broadcast television & sports) between the two displays. All video is shot in 30fps, which goes evenly into 60 or 120 so there should be no perceptible difference.

Really, to see a difference you need to have a source that is 1080p / 24fps. As only Blu-Ray outputs that type of signal you will not gain any real benefit without one.

True? False? Partially correct?

Pretty much right. There are actually a couple possible sources for 24fps content, as film-based DVD's have been requiring us to do a 3:2 pulldown for over a decade now. Very few players out there actually offer a 24p output of DVD content, though, but some Blu-ray players are capable of it in addition to their ability to output film-based Blu-ray content at 24p.

There's one other possible benefit to 120Hz, from what I've read, although I've heard mixed things about it. Even on standard content, LCD's can have a hard time with fast motion - as a solution, manufacturers are using 120Hz and various proprietary processing modes to help smooth out that fast motion content. I've seen comments from a fair number of TV reviewers indicating that this often makes film content seem more like video (which they don't like). I've also found that these modes often can't be used without interfering with the goal of accepting a 1080p/24 signal and displaying it as cleanly as possible (the TV applies that frame interpolation instead of just repeating the frames five times) - you have to pick one or the other.

Thanks gonk. The part about using 120Hz as a solution to fast motion issues explains some other posts that I've seen where people say that the image doesn't look right. The common complaint seems to be that it almost looks like it has been speed up like the campy movie effects from the 70's.

When I've talked TV's with OPPO, they have indicated that their standard procedure on setting up an HDTV in their testing lab is to disable any of these 120Hz modes that are designed to smooth out fast motion because they usually don't like the effect. (Plus it adds a layer of unpredictable video processing that's not appealing when testing disc players, which is what they are most likely to be doing.) That matches what I've read from most reviewers.

Gonk, your explanation of what they do at Oppo raises another question. How difficult is it to switch the 120 hz modes on and off? For example, could you easily program a universal remote to turn it on when watching a TV-like source and off when watching a DVD-like source?

Depends on the TV, I suppose. For the ones I've looked at, it's a setting buried a level or two into a setup menu - a macro could probably be done, but it's on the tricky side.

And there are some TVs that don't let you do it at all. A recent review in Home Theater (can't find it online) of a fairly pricey LCD with 120 hz criticized it fairly strongly for not giving any ability to optionally permit 60 hz processing to avoid what was described as making film material look like it was shot on video.

Excellent point - HDTV's and their video processing get complicated in a hurry, and the controls available to the users are sometimes not what they should be...