Is 23.976 "true 24p"? at DVinfo.net

Ian E. Pearson · August 12th, 2005, 08:13 PM

I'm not sure if I fully understand this so bear with me. The hd100 is supposed to shoot true 24p, so that the framerate would match perfectly for film-outs. Yet Barry Green's clips are actually 23.976. If the 24p framerate of the camera is actually 23.976 then you would actually have to speed it up a tad to match film. Right?

Patrick King · August 12th, 2005, 08:28 PM

Quote:

Originally Posted by Ian E. Pearson

I'm not sure if I fully understand this so bear with me. The hd100 is supposed to shoot true 24p, so that the framerate would match perfectly for film-outs. Yet Barry Green's clips are actually 23.976. If the 24p framerate of the camera is actually 23.976 then you would actually have to speed it up a tad to match film. Right?

Ian, you are talking about speeding it up 3.6 seconds if the film is an hour long. I'm thinking you can't tell the difference.

Ian E. Pearson · August 12th, 2005, 09:01 PM

I'm not worried about timing. I'm worried about rendering. Rendering an entire project to account for that 3 seconds is what troubles me.

Are all "24p" cameras actually 23.976? What about CineAlta? Is there a camera that does record exactly 24p? Or am I making a big deal out of nothing?

David Newman · August 12th, 2005, 10:01 PM

" big deal out of nothing?" -- Yes. :)

Many (or not most) 24p workflows are actually 23.976. But as long as you know your timebase it does matter where you use 23.79, 24 or even 25 for a film workflow. Camera's like CineAlta can be set for either 23.976p or 24p.

Barry Green · August 13th, 2005, 06:02 PM

The CineAlta can shoot at 24p or 23.976.

Many film cameras have the option of shooting crystal-sync at 24fps or 23.976 fps.

And film projectors run at a nominal 24fps; you'd probably be surprised at how off-speed they are. Urban legends abound of small theater owners cranking up the projectors to 26fps so they'd get through the movie quicker so they could squeeze another screening in!

Usually the choice between 24p and 23.976, at least in a film camera, is made based on where the footage is destined to be edited and where it will be exhibited. If editing on film for a film projection, you'd shoot 24fps. If editing on video, intending for a video release, you'd shoot 23.976. The difference is really minimal -- you're talking about a 0.1% speed difference. Compare that with the difference of shooting 24fps film, and then speeding it up to 25fps for exhibition on PAL television -- that's a 4% speed change! 40 times as much as the difference between 24p and 23.976p.

I would expect all "24p" video cameras really operate at 23.976 fps -- DVX, SDX, SPX, XL2, HVX, HD100 -- I'm sure they all do. They are (after all) video cameras, making video destined for editing and playback on video. 23.976 is the right frame rate for that.

Graeme Nattress · August 13th, 2005, 06:23 PM

It's all got to do with the ludicrous NTSC frame rate of 29.97fps. To get "24p" to work, and to be able to play out on an NTSC, it's got to run at 23.98fps, not 24.00fps. Every film shot at 24.00fps that you see on TV is really at 23.98fps (with 3:2 pulldown added to make it 29.97fps). It's not anything really to worry about, and because it's an utter necessity, everyone who does film out can handle it no bother.

Graeme

August 12th, 2005, 08:13 PM	#1
Ian E. Pearson Regular Crew Join Date: Jul 2005 Location: Greeley, CO Posts: 52	Is 23.976 "true 24p"? I'm not sure if I fully understand this so bear with me. The hd100 is supposed to shoot true 24p, so that the framerate would match perfectly for film-outs. Yet Barry Green's clips are actually 23.976. If the 24p framerate of the camera is actually 23.976 then you would actually have to speed it up a tad to match film. Right?

August 12th, 2005, 10:01 PM	#4
David Newman CTO, CineForm Inc. Join Date: Jul 2003 Location: Cardiff-by-the-Sea, California Posts: 8,095	" big deal out of nothing?" -- Yes. :) Many (or not most) 24p workflows are actually 23.976. But as long as you know your timebase it does matter where you use 23.79, 24 or even 25 for a film workflow. Camera's like CineAlta can be set for either 23.976p or 24p. __________________ David Newman -- web: www.gopro.com blog: cineform.blogspot.com -- twitter: twitter.com/David_Newman

August 13th, 2005, 06:23 PM	#6
Graeme Nattress RED Problem Solver Join Date: Sep 2003 Location: Ottawa, Canada Posts: 1,365	It's all got to do with the ludicrous NTSC frame rate of 29.97fps. To get "24p" to work, and to be able to play out on an NTSC, it's got to run at 23.98fps, not 24.00fps. Every film shot at 24.00fps that you see on TV is really at 23.98fps (with 3:2 pulldown added to make it 29.97fps). It's not anything really to worry about, and because it's an utter necessity, everyone who does film out can handle it no bother. Graeme __________________ www.nattress.com - filters for FCP

August 12th, 2005, 09:01 PM	#3
Ian E. Pearson Regular Crew Join Date: Jul 2005 Location: Greeley, CO Posts: 52	I'm not worried about timing. I'm worried about rendering. Rendering an entire project to account for that 3 seconds is what troubles me. Are all "24p" cameras actually 23.976? What about CineAlta? Is there a camera that does record exactly 24p? Or am I making a big deal out of nothing?

August 13th, 2005, 06:02 PM	#5
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	The CineAlta can shoot at 24p or 23.976. Many film cameras have the option of shooting crystal-sync at 24fps or 23.976 fps. And film projectors run at a nominal 24fps; you'd probably be surprised at how off-speed they are. Urban legends abound of small theater owners cranking up the projectors to 26fps so they'd get through the movie quicker so they could squeeze another screening in! Usually the choice between 24p and 23.976, at least in a film camera, is made based on where the footage is destined to be edited and where it will be exhibited. If editing on film for a film projection, you'd shoot 24fps. If editing on video, intending for a video release, you'd shoot 23.976. The difference is really minimal -- you're talking about a 0.1% speed difference. Compare that with the difference of shooting 24fps film, and then speeding it up to 25fps for exhibition on PAL television -- that's a 4% speed change! 40 times as much as the difference between 24p and 23.976p. I would expect all "24p" video cameras really operate at 23.976 fps -- DVX, SDX, SPX, XL2, HVX, HD100 -- I'm sure they all do. They are (after all) video cameras, making video destined for editing and playback on video. 23.976 is the right frame rate for that.