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Some clarity on 24p, please

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Adam Clark
Some clarity on 24p, please
on Feb 10, 2011 at 10:58:10 pm

I have done searches, read a lot of posts, wikipedia etc. and this is still not making sense to me. I am almost embarrassed to make yet another post on the matter since it seems so redundant. However, I am touching on fps in a college thesis paper and I need to be absolutely clear on 24p.

My understanding and please correct me if I'm wrong (I probably am, that's why I'm here)...

There is a "true" film 24p and there is a video 24p which is actually 23.976. When speaking in terms of video, when one refers to 24p they really mean 23.976? Is there a general misconception about the term 24p or is it all in my head?

I know that working at 23.976 for video is important because it is more compatible with 29.976 for pulldown, is that right? So, are there any instances when you would actually work at true 24p in AE?

Perhaps the sad truth is the answer I am looking for is not as straightforward as I would like, but thank you for enlightening me on the subject.


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Dave LaRonde
Re: Some clarity on 24p, please
on Feb 11, 2011 at 2:01:10 am

It's really not as tough as you think.


[Adam Clark] "There is a "true" film 24p and there is a video 24p which is actually 23.976. When speaking in terms of video, when one refers to 24p they really mean 23.976?"

That's correct. It has to do with the NTSC frame rate of 29.97 fps. It was originally 30 fps, but the National Television Standards Committee (aka NTSC) changed it in 1953 to accommodate a color signal within a previously black & white TV system.

Many makers of cameras and editing software will refer to the frame rate as "23.98". Don't be fooled: it's 23.976.



[Adam Clark] "I know that working at 23.976 for video is important because it is more compatible with 29.976 for pulldown, is that right"

Yes... sort of; the frame rate it's related to is 29.97 and not 29.976. When doing this stuff, the correct fractions count. A lot.

I'll assume you're familiar with the genesis of 3:2 pulldown.

Many cameras in the below-$10,000 range shoot 1080 video at 24p, but with 3:2 pulldown in the video. Generally, it must be removed prior to use. If you're cutting a show that will require NO effects of any kind, you can get away without removing the pulldown, but you have to make sure you make your cuts on whole frames and not split frames; it's tricky. It's always best to remove the pulldown.



[Adam Clark] "are there any instances when you would actually work at true 24p in AE?"

Yes: when working with true 24fps footage: image sequence scans from film, 2K files, 4K files, certain DPX files, etc. Video cameras DO exist that shoot at 24 fps, but it's doubtful you'd work with the footage; typically, they're equal in value to a brand-new Corvette... lenses, matte box, rails, viewfinder and sound recording equipment are sold separately.


Kapiche?

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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