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"True" 24 fps


Jeff Wexler
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I am filling in on a movie next week and when I asked the DIT (who was my only contact) he said they are shooting Alexa XT at a true 24 fps. This always raises a flag and I replied that in the past there have been people who have specified 24 fps but what they really meant was 23.976 (you know the drill). Well, evidently I ruffled his feathers a bit, his reply to me: "If you run across a DIT who says 24fps and means 23.976, then he should turn in his wave form." I think my mistake was implying that it has been a DIT in the past that has made this mistake (which is not the case).

 

So, I guess I set everything at 24 fps --- I actually have never done this before.

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I think we need to bring back mathematical precision back to this whole framerate issue.  It should be written 24.000 fps (in my opinion).  It is true that if someone says 24fps, they mean 24.000, while if someone says 24p, that generally infers 23.976 fps.  The problem is that most non-technical people don't understand this distinction in seemingly interchangeable nomenclature.  I noticed that on the new GH4, since it allows you to set system frequency (NTSC, PAL, or cine) that there are going to be a whole lot of amateur filmmakers shooting at "true 24fps" because they think it is better.

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Not feeding the camera any audio --- so I guess I didn't read Scott's post properly (I don't need the Alexa to record any of the sound, this is pure double system). I mis-understood "will only record sync sound" to mean that if not set to 23.976 it cannot be synced to my recorded sound. Silly, I know, but I'm just going to go with my settings (for jamming purposes) of a straight 24.0.

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A feature I worked on last summer was shot on an Alexa at actual 24fps.  Sound was recorded at 48kHz.  I was thinking that I sent a scratch track to the camera but I've slept since then so can't be sure about that.  I recall we did jam the camera.

 

One thing to check on the Alexa is that the sensor rate and frame rate coincide. 

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i have mixed a couple of films with the Alexa where the camera and myself were recording at 24fps. though this is in the land of PAL where things are less confusing.

havent yet received any phone calls screaming at me that they cant get sound and picture to sync up.

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Yes, I have seen a handful of productions shooting at 24.00fps with true 24-frame timecode, though most are 23.98. Sounds to me like the DIT was being very snippy to Jeff, which is unfair since this was a totally legit question. Somebody should have this information written down so that it's an etched-in-stone memo with everything fully spelled out.

 

In truth, a lot of different workflows can work. All it takes is for every department to agree on it. I think generally editorial makes the request, but there may also be a VP of Post-Production at the studio who weighs in on the final decision. 

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Is it that, if it's a movie for the cinema then 24.000 fps and if for TV then 23.976 might suit the workflow better, as 24.000 fps would need to be made 23.976 fps for USA TV somewhere along the line and it would save that conversion, if it's destined for TV from the start?

 

The many films made for the cinema (24.000fps) that are regularly shown on TV, at 23.976 no-one notices the conversion?

23.976 FPS = 24×1000÷1001.

 

Here's a pretty detailed explanation for 48048 -

http://www.trewaudio.com/audioflow/48048-khz/

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If you are filling in, perhaps contact the mixer who was previously working the show to confirm sync settings for sound? I understand he or she may not be your point of contact for the show, but it may be worth trying to reach the person anyway.

 

Let us know how everything ends up working out.

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I don't see a way to set the Alexa camera audio SR to anything other than 48k--is there one?   A workflow that used 48.048 SR for audio and 24 fps video seems like it is headed for a 23.976 post and a pull up later on, maybe @ the DCP stage?

 

philp

apologies for lack of clarity.  sampling rate was for the sound recorder, when shooting double system.  I have never had to feed an alexa, so I don't know the audio settings of the camera at all. as rob sharman mentions,  I have used this workflow for WB shows, when filling in.  I routinely get a call and email from the mixer I am filling in for,  or doing second unit for, with all the specs spelled out. 

 

ao

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Here's a question: do digital cinema projectors in theatres work at 24fps or 23.98?

The projectors will run anything...23.9,24,25,29.9 etc.

When I look at the server that runs the Digital Cinema Package, it identifies the media as 

24psf 12bit 444 JPeg2000 250Mbps 48k PCM audio for a 2048x1080 flat picture, 2048x 858 for scope. (2K)

Progressive Segmented Frame..same as HDCamSR. Simulates a 24fps film projector with a 2-bladed shutter.

But I'll have to go back and look again, as my memory is constantly changing, along with all this new 

stuff that comes and goes.... a re-inventing of the wheel......

Doesn't make any difference what you shoot at, master house will conform.

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You're right Philip. In Sweden we almost always shoot at 25, and it's all good, until we want to go DCP. We can't shoot at 24 or 23.976 because many festivals and other formats which are more widely used can do 25. No biggie, but still. I think the projectors are being updated with new framerates, at least I think so.. Heard people talking about it

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Jose finally said: " contact the mixer who was previously working the show to confirm sync settings for sound? "

also checking in with post, as you typically do.

ao: "  I routinely get a call and email from the mixer I am filling in for,  or doing second unit for, with all the specs spelled out.  "

maybe there is something we don't know about this "filling in", but when doing so under any circumstances, if the production expects things to run smoothly, they need to provide complete, proper specifications; if there was an issue, then the issues need to be resolved, and workflow verified.

and, BTW, I would agree that the DIT was a bit brusque, and will probably be surprised when s/he learns of JW's level of experience and competence.

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