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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

24P or 23.98?

David Battistella

David Battistella

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What frequency is RED recorded at. Will the 24P footage actually be 23.98 for use in NLE's or will we be working in true 24fps? I guess it is the difference between 59.94 and 60HZ.

Can anyone shed light on this?


David
 
Like Jim, I've always understood that we would have the option of either. Hopefully we will.
 
when would you choose one over the other?
 
23.98 is a carry-over from 59.97 (60) Hz NTSC and most "24fps" video systems operate at 23.98Hz and not truly 24fps. You would choose 23.98 if you knew for a fact that everything you were shooting were going to be placed into a 59.97 timeline or integrated with a lot of 59.97 footage. 23.98 gives a perfect 2:3:2:3 telecine frame conversion to NTSC 59.97.

If that isn't your concern or you will be targeting theatrical distribution and output to film or digital projection, then 24fps is the way to go. Some of this will also be dictated by your NLE and post software and what they support. Be sure to choose the right one given all these circumstances or your audio will drift away from your visuals over time. In the video to film world, 23.98 is often scaled and the audio is scaled/stretched along with it and most of the time it's not noticeable.
 
23.98

23.98

I am a bit confused by this as well. I thought that even if you want a film out you can still use 23.98 and have the benefit of going straight to video as well. Is this not correct? Does shooting at 24 somehow disadvantage the film out?
 
In most cases, no. The difference is very slight. Just be sure your post workflow can account for it and it's no big deal. But 2 hours of footage (7200 seconds) finished or shot at 23.98 and then played back at 24fps will finish up 6 seconds faster -- 7194 seconds.

No big deal, just be aware that going from 23.98 to 24, somewhere along the line audio will have to be scaled as a whole, or trimmed and centered per shot. Or one frame every 12 seconds or so will need to be repeated.
 
Jeff Kilgroe said:
No big deal, just be aware that going from 23.98 to 24, somewhere along the line audio will have to be scaled as a whole, or trimmed and centered per shot. Or one frame every 12 seconds or so will need to be repeated.
Click to expand...

Hey Jeff,

I have to disagree slightly here. It can be a very big deal.

Let me illustrate:

1) Dual system on-set. Camera at true 24. Nagra at 59.94 (happens all the time)
2) Downconvert from camera is taken at 59.94 for offline and DATs or CDs are made from audio masters.
2) Offline editor digitizes everything into an Avid at true 24. When audio goes out of sync - as it does very quickly - he just sort of ignores that, adds an edit and slips audio. The human eye is incredibly sensitive to lip-sync that is not right. The difference between 24 and 23.98 will be evident very quickly.
3) Several hundred edits later, timeline is finished and an EDL/AAF is exported to Online
4) Online takes the EDL and (being a good and conscientious Online Editor) digitizes tape at 24, and audio at 23.98, and then conforms. Everything is hideously screwed up. Many hours later...

That's just one I can think of. Now that HD has been around for awhile, labeling has gotten much much better, but it used to be that everything was labeled "24p" and an Online Editor had to guess as to frame rates.

And the ProTools guys are screaming at you because you screwed up the layback. Those sessions sucked.

Lucas
-----
Hates the Subcarrier Frequency
ASSIMILATE, Inc.
LA, CA, USA
 
Jeff Kilgroe said:
In the video to film world, 23.98 is often scaled and the audio is scaled/stretched along with it and most of the time it's not noticeable.
Click to expand...

What does it show up as when the scaling becomes noticeable? Pitch shift in audio?

Any examples we can look at?
 
FYI all of the feature films I'm aware of that have been shot with the CineAltas have been clocked at 23.98. Examples like the two Star Wars, all the RR films (Sin City, Spy Kids, etc.) Sky Captain, etc...
 
All HD cameras as far as I know are shooting 23.98 but the labeling/display is always 24. I don't know which HD cameras out there actually give a specific option to shoot explicitly 24.
 
luki said:
I have to disagree slightly here. It can be a very big deal.
Click to expand...

Yes, I suppose it would be a rather big deal in situations like you just mentioned. I guess I was just saying it isn't that big a deal if everyone is on the same page and deals with a 23.98 to 24 conversion properly.

mdo said:
What does it show up as when the scaling becomes noticeable? Pitch shift in audio?

Any examples we can look at?
Click to expand...

If the audio is squeezed or stretched by 0.04% it may or may not be noticeable, depending on the content and the audience. I think in most cases no one will notice. I'm not sure if there would be an audible change or shift in pitch or not. ...I'm not much of an audio guy. I did a quick google search of 23.98 24 and audio and came up with tons of possible links to follow.
 
opcode said:
All HD cameras as far as I know are shooting 23.98 but the labeling/display is always 24. I don't know which HD cameras out there actually give a specific option to shoot explicitly 24.
Click to expand...

Actually, I'm reasonably sure the CineAltas can shoot true 24 fps as well as 23.976.
 
luki said:
1) Dual system on-set. Camera at true 24. Nagra at 59.94 (happens all the time)
Click to expand...

If this happens all the time, it speaks very poorly of the tech skills of the folks involved.

We never those sort of mistakes shooting sync sound with true 24fp film fifteen years ago, and today there's simply no excuse.
 
Jim Arthurs said:
Actually, I'm reasonably sure the CineAltas can shoot true 24 fps as well as 23.976.
Click to expand...

I don't know about the F900... I *think* the F950 does. The F23 DOES shoot 24fps.

Edit> The Panavised F900s like the ones used on Star Wars shoot actual 24fps.
 
Film cameras usually shoot at 24 fps but are transferred at 23.976 fps because of NTSC (59.94i). So most of the sound post, until recently, has been done using NTSC dubs of the cut footage provided by the picture editor. It may be changing more and more as footage is provided on Quicktime files, but again, I believe often it is NTSC, not true 24P. I seem to recall a sound supervisor telling me that in the final steps of the mix before the print master is made (or maybe between the print master and the optical neg), an adjustment in sound speed is made to convert something posted at 23.976 to 24.

I shot one of the first F900 features, "Jackpot", and used the 24P setting, not the 23.98P setting (the camera allows both). The only problem I heard was that the editor ended up fixing some of the sync in the final mix session. Anyway, since then I've only shot HD in 23.98P and the sound post seems to work fine.

It's all a bit silly since nowadays one should be able to work at true 24.0 fps throughout the post process.

Has no affect on a film-out, which is a 1:1 frame transfer, just is a sound issue regarding sync.

Being a cinematographer, not an editor nor a sound editor (though I worked two years at a sound post house doing data entry), I don't have a total grasp on all the issues, but I've heard someone tell me that Sony regrets ever making 24P an option on the F900 because everyone really should be using 23.98P for post reasons. Unfortunately, even 60i HDTV post seems to have carried over the NTSC issues; when a 24 fps movie is mastered to HD for home video, it is transferred at 23.976 fps.
 
I would recommend 23.976 over 24.0 for a lot of folks - see blog entry today on The Nines and how 24.0 hindered some parts of the affordability of their workflow:

http://www.hdforindies.com/2007/08/lots-of-how-done-info-on-my-client-john.html

If you go true 24.0, you're locked on target for filmout.

If you go 23.976, it makes gear interoperability easier along the way, and you'll have to tweak retime audio ever so slightly at the end. I find that easier to deal with, personally.

-mike

PS - and yes, the real/pro cameras (F900/950/F23/Varicam/Viper/etc.) can all do 23.976 or 24.000 frames per second. "Choose wisely."
 
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