Frame loss and perception

J. Anthony Gonzales · January 10, 2005

How noticeable to the viewer is a frame drop within a continuous shot? This would be shooting at 24fps, MOS. Let's say you have a shot that lasts 1 minute. If you were to cut one frame every second out of the shot, how "jumpy" would it appear? How long between drops before you wouldn't really notice? Every 2 secs, 5 secs, 10 secs? I also assume the more motion in the shot, the more noticeable it would be?

Thanks,

John G.

Justin Hayward · January 10, 2005

Try it. It would be very noticeable.

Dominic Case · January 10, 2005

When 24fps film is telecined to PAL, there is the possibility of transferring at 24fps: this is done by repeating one field (half a frame) every half second.

While this ensures that sound is kept on pitch without any digital repitching (which wasn't even available when the 24/25 pull-down was first being done), and also mainians the correcct running time for the production, people by and large don't do it, for the simple reason that the jitter in the action is believed to be unacceptable. So they simply transfer 24fps material at 25fps.

It's really only noticeable in shots with a smooth pan or - occasionally - a smooth subject movement (though how many of those are there?). But if adding one field every half second is a problem, I would expect that dropping a frame every second or so would be at least as objectionable.

John Sprung · January 10, 2005

Unless the shot is absolutely static -- say an establishing shot of a building -- it's very noticeable and objectionable. I tried it once. It took about ten seconds to decide never to do that again.

-- J.S.

Filip Plesha · January 11, 2005

There are two frame jumps in gladiator in the battle scene in the arena.

I think they are intentional because they do go along with the whole jerky style

of the battle scenes (it was 90 degree that they used for some battle scenes, can someone confirm this?) but I'm not sure.

But it is clear that frames are missing, you can look there for the reference.

Phil Rhodes · January 11, 2005

Hi,

> When 24fps film is telecined to PAL, there is the possibility of transferring at 24fps: this is done by

> repeating one field (half a frame) every half second.

Yeah, and it looks awful!

Phil

Michael Nash · January 11, 2005

You see this quite often in movies that have been "time compressed" for television, and it drives me nuts. I don't know the precise frequency of dropped frames, but you notice it in long dolly or pan shots, not so much in dialogue. But then again maybe dialogue sequences are spared the worst compression, and instead it's reserved for those wider shots where you don't see as much lip-synch.