24P question

[John Sharaf]

HD video shot at 24fps and 180 degree shutter with a 3:2 pull down applied should look exactly the same as film shot at the same rate viewed on video after telecine. Are you looking at the HD footage with pull down (from Cine Alta)?

JS

[Randy Strome]

I don’t believe the pulldown has been applied in any of the posted examples. For instance, the ones in Matt’s tests:

https://www.pairofhands.net/Ex1%20vs%20HVX%20Shootout.html

[John Sharaf]

Like I said, if you’re viewing on a monitor without 3:2 pulldown added, then the motion is not accurate and it might studder, jutter or whatever you describe as unpleasant. Only if filmed out and viewed on a motion picture projector at 24fps, where the dual bladed shutter and the effect of persistence of vision in the dark theater would effectively smooth out the motion could you view the proper effect. This is a particular flaw in the method Sony uses in the Cine Alta and the “native” Panasonic formats, such that “processing” must be applied in playback for proper motion display. Of course the alternative of saving storage space has many advantages too.

JS

[Randy Strome]

Very helpful explanation. Thanks John!

[Don Greening]

Since we’re on the subject, I was just curious how or what is done to ensure smooth motion when showing a film on television that was originally destined for theaters.

– Don

[Craig Seeman]

[john sharaf] “This is a particular flaw in the method Sony uses in the Cine Alta and the “native” Panasonic formats, such that “processing” must be applied in playback for proper motion display.”

Can you describe the flaw and the processing to fix it?

[John Sharaf]

Craig,

The problem is self evident when you view the output of the Cine Alta at 24p on a HD CRT; it flickers like crazy. This is even though the monitor doubles the frequency rate to try and smooth it out. On LCD’s it’s not apparent because it has an even higher refresh rate.

The solution of course is tho add the processing of a 3:2 pull down; this doubles and triples up successive frames and smooths out the motion. This processing is added in the playback deck and takes place when you make downconverts or dubs. In the Panasonic the logic of 24pN is the same as Sony’s to use less storage (in this case precious P2 capacity) and then extrapolate the frames out later in post, or continue to save storage by editing in a 24p timeline. Remember that 24 is only 40% of 60 so that’s the amount of storage you’re saving – that’s a significant amount. In the end of course, if you’re not printing out to a 24p use (like film out or some DVD pressings) at that point you add the “processing” to make it compatible with 59.94 type CRTs.

I hope this helps. Perhaps “flaw” is the wrong word, but I hope you can now see how the processing takes place.

JS

[Craig Seeman]

John, I understand that, I’ve been a video engineer. What I haven’t figured out is why 23.98 video with 1/48 shutter does NOT look like 24fps film. I dislike 23.98fps video and can’t fathom why some people say it looks “like film.” (almost) Matching frame rate and shutter angle doesn’t really seem to be a match in motion.

In my opinion video with pull down still doesn’t look like film with pull down. I can’t think of a technical reason why though and was hopping you had.

I do know that many people shoot 23.98p video because it’s easy to transfer to 25fps or 29.97fps.

30p can have issues going to 25fps given the frame math an the lack of interlaced fields to “split.”

[John Sharaf]

Craig,

I guess this is what makes horse racing!

I started in film, shooting quite a bit of 16mm that was telecined for broadcast on television newsmagazines, so I feel like I have some point of reference, and I feel that HD video shot at 24p does look quite a bit like film when displayed on video screens. The manufacturers have done a good job in imitating the frame rate (exactly) and some include the pulldown (and even variants like “advanced pulldown’), they imitate the gamma curve with various “film looks”, “hyper gamma” and “cine gamma” settings and finally the video “noise” approximates the grain inherent in film, especially in the almost grainless look of the most modern stocks.

I don’t mean to be a contrarian here, but I have to respectfully disagree with your assessment of the success of 24fps HD in looking like film. Technically the only subtle difference is the action of the shutter itself; in the film camera it moves either side to side or top to bottom, whereas in the video camera it captures the frame/field in one fell swoop. I don’t think that this subtle difference is perceptible, especially enough to distinguish the look as not being filmlike.

I think short of a side by side comparison on identical video displays of the same shot on film and HD you could not really state with much authority that they are different, and in fact, were you to do such a test, I think you would find, once and for all, that you were mistaken.

That is not to say that 24p is the be-all and end-all frame rate. You are correct in saying that it is often used because of the ease in which it converts to 25 (for European release) and 30 (for NTSC use). In most cases, the 30fps frame rate is actually a better choice, in that it remains progressive, which all the inherent motion and sharpness benefits over interlaced, and it looks more “filmic” and less “live”. If the bean counters had not had such an influence as the have always had, this might have been the standard frame rate from the beginning of sound film, rather than 24; but financial considerations have and will always have an influence over technical standards.

Finally, if for aesthetic or creative reasons you don’t like the look of video at 24fps, you still have the alternative of shooting on film or shooting video at the 30 frame rate (if you prefer that).

JS

[Craig Seeman]

Contrarian?

[john sharaf] “Like I said, if you’re viewing on a monitor without 3:2 pulldown added, then the motion is not accurate and it might studder, jutter or whatever you describe as unpleasant.”

23.98p without pull down on a monitor that can play 23.98p . . . looks like 23.98p.

Computer monitor have no problem with 23.98p native. Many HDTVs can play 23.98p (and some really do a bad job of it).

Many editors don’t understand the concept behind the cadence (both “standard” and advanced) when pull down is added and that can certainly impact the look if one is editing 23.98 with pull down added in 29.97 time line.

It’s interesting that I’m not the only one who sees motion issues with 23.98 and video. I just viewed Doug Jensen’s EX1 training video and while he doesn’t verbalize it well, he does state clearly that he prefers 30p to 24p and shows examples of the same scene shot both ways. The scenes are displayed in standard def on a 29.97 TV set of course. I don’t recall if he mentioned the shutter angle (or speed) but nonetheless I’m sure he and many other very experienced DPs (which I don’t claim to be) see what I see.

In short, I can’t nail why but 24fps film with proper pull down played 29.97 interlace looks different that video 23.98 with pull down played on 29.97 interlace. My eyes see it and I do know I’m not the only one who does.

There are also many means to add that pull down and maybe that’s part of the difference. “Video” shot at 23.98 and played at 24fps in a movie theater is another story. MANY films are shooting with digital cameras at 23.98 and shown in theaters at 24fps and they look fine.