I got a question from a friend of mine, and I thought it might be worth sharing my answer with a wider audience. He asks:

“What’s the short answer for why new 120hz screens make films look like video? I don’t know if you have had a chance to observe this yet, but it will effect you because it makes everything look like the ‘behind the scenes’ footage on a dvd, or raw dailies. People seem to love it.”

Well, I can attest to the fact that not everyone loves it, in fact the cinemaphile/home theater boards are filled with invective regarding how this feature despoils the cinematic experience, and I completely agree with them. I’m all about respecting the filmmaker’s intent regarding how they wanted the film to look, so whatever framerate they created their program using, that’s the framerate I want to watch it at.

The reason for the difference in “look” between 24p video viewed natively and 24p video that’s been converted via 120hz digital magic is virtually identical to the difference between 24p film and 29.97 video frame rates. We’ve all grown up with juddery 24p frame rates looking “cinematic,” even though the motion sampling is, strictly speaking, pretty crude compared to what is now possible.

On the other hand, since the motion sampling of interlaced 29.97 video is effectively 60 fps, “video” motion has traditionally looked much smoother, more “real life,” or more like a TV newscast.

The newer 120hz displays use motion estimation to generate/interpolate new frames in-between the original frames of the 23.98 image stream on a DVD/Blu-ray, and so the “cinematic” motion of 24p is changed into the “non-cinematic” look we generally associate with video, all because of the introduction of a smoothness of motion where there was none before. The result, to my eye, is that classic motion pictures end up looking like a shot-on-video sitcom.

Incidentally, speaking for myself I find that the reverse can also be distracting. I’m increasingly seeing 24p-acquired video used in programs like the PBS newshour, the result being a somewhat “cinema” look within traditionally interlaced video programming, which I confess looks a bit odd. I’m just not used to it, and I believe this effect is solely based in what we’re used to.

It’s entirely possible that, someday, the next generation may get so used to 60p that 24p will be looked upon as quaintly as silent film or black & white, (at least, if James Cameron has his way). However, there are so many advantages to the low-bandwidth of 24p that I suspect, similar to interlacing, 24p motion sampling will be around for a long, long time. (And I’m not even going to get into the debate over the “intrinsic” cinematic value of shooting one’s projects 24p and 24p only, this particular article is about watching movies, not making them.)

My friend went on to reply:

I can see that showing the same thing 5 times would look different than showing me the thing, and a thing, then a half a thing mixed with half of the next thing. [My note: this is a fantastic description of 3:2 pulldown insertion] I just wasn’t expecting it to change the character of the images so much. Seems like the old way is closer to what it looks like in the theater. I wish my dvd-blu-ray player could just do 24 frames without the pulldown. You kids, give me back my vinyl 78s!

I suspect most of you already know what my reply is, but for those who don’t, I’ll enlighten you.

If you’ve got a good flat-panel display (television or projector), and especially if you’re using HDMI (and really, who isn’t anymore), you should be able to set up your player/display combo to play back actual 23.98 right now.

You usually have to enable the settings manually within your gear’s menus, but the DVD specification (and now Blu-ray) has always allowed distributors to author a DVD with an encoded 23.98 video stream—all players are supposed to do 3:2 pulldown insertion when necessary in order to display content on a non-24p-capable TV. If the TV can handle 23.98, then the player can send it directly via Component or HDMI.

So there you go. If you get a new TV and your movies look like television news, do yourself a favor and disable that pesky 120hz interpolation mode. You’ll be surprised at the difference.

Added 1/12/11—There’s an interesting thread in the comments. Nothing is ever simple! Also, it was pointed out to me that Tom Lehrer, the mathematician, songwriter, and satirist, did not in fact host the News Hour. That would be Jim Lehrer. Of course, now it’s just the News Hour, so I’ve eliminated the names altogether.