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pull down issue


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#1 Pablo Galarza

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Posted 08 April 2011 - 08:29 AM

Hi
I shot on film an image from a PAL tv screen, so it was shot at 25 fps. As there was music on it, the director didn't want to change the audio pitch, and we went with a 25 to 24 fps pull down on the image. In the projection, I found a very important flickering which wasn't there before the pull down. When comparing it with a previous MOS copy made before the pull down, I found a very little flickering as well, but barely noticeable. I assume that the pull down changed the frequency of the flicker which turned it into a problem.

As the audio is fully finished, the producer wants to solve the problem taking care of the image only.
I can't figure out how, if there's a way. So, if anyone has any ideas or had a similar situation before, i would very much appreciate the help.
Thank you very much in advance.
Pablo Galarza. DP.
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#2 Damien Andre

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Posted 08 April 2011 - 11:45 AM

you could seperate the audio from the video then slow down the video the drop the music back in. burn it to a new dvd or however youre playing it
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#3 John Sprung

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Posted 08 April 2011 - 02:05 PM

Trying to understand exactly what happened here.... You shot film at 25 fps of a PAL TV set. The relationship between film frames and PAL frames was basically carved in stone at that point. You had the film developed, and then what? Workprint? Telecine? How did you view it in a way that didn't flicker, and how did you view it in a way that did flicker? That you were able to see it once without flicker is a good omen -- it means that the image on the film is OK.




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#4 Pablo Galarza

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Posted 09 April 2011 - 09:25 PM

Hi
Thanks for your answers. I'm sorry I wasn't clear.
After the film was developed, it was transfered to video for editing purposes, and after that, we saw a 35 mm print, blown up directly from the original 16 mm negative (optically), where the flicker was barely noticeable. The flicker became important when I saw the first final print with sound, after the frame rate of the image was modified.
Thank you.
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#5 John Sprung

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Posted 11 April 2011 - 01:33 PM

For the 25 to 24 conversion to accentuate the flicker, it might be that the flicker was a slow change from frame to frame, and dropping frames takes out a mid-level frame here and there, causing a bigger jump. If that's the cause, the most cost effective solution would be to go back to the original frames, stretch and pitch shift the sound to fit, and just let that sequence play 4% slower than it was shot. This is done very commonly for shows from PAL countries imported into NTSC/24p countries, like the BBC shows on PBS here. It works very well, no problem at all.




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#6 Pablo Galarza

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Posted 12 April 2011 - 09:26 PM

Hi
Thanks for the answer John.
My first solution was to change the audio pitch keeping the original frames in the image. But, as the optical soundtrack is already finished, I was looking for another possible solution which doesn't force us to redo it. I guess there is none.
Thank you.
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