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Discussion Starter · #1 ·
We talk about genlock on 24fps to a 48/72fps output for a judder free smooth playback, just like the original film persentation.


But isn't NTSC at 59.94i? Which make it a 29.97p. Then after 3/2 pulldown it becomes at 23.976fps, right?


If real film is shoot at an exact 24.00fps, that makes NTSC rate a tiny bit slower, right? A 2 hours film becomes 2 hours and 7.2 seconds.


So 48/72Hz genlock really means 47.952/71.928Hz, right?


Maybe we need a video processor to speedup NTSC to the REAL 24fps film rate then! :D


regards,


Li On
 

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Quote:
Originally Posted by Li On
We talk about genlock on 24fps to a 48/72fps output for a judder free smooth playback, just like the original film persentation.


But isn't NTSC at 59.94i? Which make it a 29.97p. Then after 3/2 pulldown it becomes at 23.976fps, right?


If real film is shoot at an exact 24.00fps, that makes NTSC rate a tiny bit slower, right? A 2 hours film becomes 2 hours and 7.2 seconds.


So 48/72Hz genlock really means 47.952/71.928Hz, right?


Maybe we need a video processor to speedup NTSC to the REAL 24fps film rate then! :D


regards,


Li On
Yes, 48/72Hz genlock really means 47.952/71.928Hz. To be precise, 48/1.001 and 72/1.001 Hz respectively.


Morpheus
 

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Discussion Starter · #4 ·
Yes, it seems with a NTSC source the exact rate is the integer/1.001.


Anyone please confrim real film rate is really exactly 24.000fps?


regards,


Li On
 

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Real film is 24.00fps. NTSC video involves a very slight speedup, IIRC. The speedup was designed to allow room for the colour subcarrier or something like that. You don't get this with PAL.


The genlocked framerates have the 1/1.001 adjustment factored in, so 47.952/71.928 as has been stated.
 

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Originally Posted by jonesthegas
Why is film 24fps anyway? Why doesn't the industry move to 30fps - it would solve a few problems.
Have you seen video at 30fps? For film; 30fps looks different from 24 fps. REALLY DIFFERENT. Many folks won’t like the adjustment they would have to go through to get used to that, including me. I think it would change the way movies are perceived. That an opinion though.


It will also look like too similar to video. Yuck.


I'm sure someone here will chime in and give a more technical reason for it though.
 

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30fps is a bad idea because it can't be properly mapped to Europe's 50Hz. It's really difficult finding *any* frequency above 24fps which can map to both 50Hz and 60Hz without too much of conversion.
 

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I'll bet 23.976fps is well with a standard deviation away from the frame rate found in most competent movie houses. No mechanical drive is really going to be that precise.
 

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Quote:
Originally Posted by jonesthegas
Why is film 24fps anyway? Why doesn't the industry move to 30fps - it would solve a few problems.
In addition to what others have said, another obvious reason the industry doesn't move to 30fps is that it would simply require a lot more celluloid, which would increase the budget of each movie and would be more expensive to physically ship to theaters.


Roger Ebert is a big proponent of the 48fps Maxivision format, which he believes would revitalize the film industry with its improved picture quality, but it will never get off the ground for the exact same reason.
 

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23.976 is not just limited to NTSC. 1080i and 720p still run at 59.94 vertical rate. So the film speed is still 23.976. This will be this way at least until NTSC goes away. Then hopefully we will revert to true 60hz.


True 24P is used in DI work but then that's not targeted for HDTV. It still must be slowed to 23.976 down if the DI data is directly comp[ressed for home video release.
 

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It'll all be moot once the digital transition is complete on the exhibition side. Yes there will always be hold outs. And I'm not talking a year from now. But eventually frame rates will be a *choice* that a film maker/DP gets to make, rather than a 1 size fits all, as 24fps film currently is.


TM
 

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Discussion Starter · #14 ·
Quote:
Originally Posted by Michael Grant
I'll bet 23.976fps is well with a standard deviation away from the frame rate found in most competent movie houses. No mechanical drive is really going to be that precise.
Hmm... more movies are being shoot with digital camera which should have no problem to stay in exactly 24.00000fps!


regards,


Li On
 

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Quote:
Originally Posted by Li On
Hmm... more movies are being shoot with digital camera which should have no problem to stay in exactly 24.00000fps!
Perhaps, but once that digital movie is transferred to a film print for projection in a theater, the projector may not run at precisely 24 fps.
 

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Glimmie, are you saying that data is actually resampled/massaged to convert from 24 to 23.976? I had always assumed 24fps video and audio is simply played back fractionally slower with no conversion done. I seriously doubt you could tell the difference.


Like Michael said, your probably not even getting that close tolerance on an actual film projector!
 

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Theatrical digital projection will still be expensive on the capture side at anything over 24 fps, since 2k and 4k cameras are designed with 24p in mind and currently require bulky outboard hard disc arrays. Anyway, there is a decrease in motion blur as you increase shutter speed- and that is a main personality trait of 24fps. Showscan technology (60mm, 60fps) sold higher frame rate as a new advancement in realism. No perceptual film grain, no motion blur, sharper images, wider color depth- but it stopped looking like "film". Their tests concluded that perceptual differences were negligable above 60 fps, so this is where they defined their frame rate. This is right in line with video's 60 fields per second rate, so eventually the future powers that be may settle into this area.
 

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kromkamp, I'm sure Glimmie just meant a slowdown.
 
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