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Choppy shot when speeding up slider footage

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Jerry Renes
Choppy shot when speeding up slider footage
on Mar 1, 2012 at 12:28:05 pm

I am shooting a cardboard set using a Canon 7D @ 1920x1080 - 25FPS and a slider on which the camera moves sideways very slow.

The slider moves really slow, using a little electric motor. I sped up the original shot in After Effects 10 times (It was 2 minutes, now it's 16 seconds long.)

The problem is, when the shot is sped up, the shot gets choppy. Real fast stuttering (See example: http://vimeo.com/37729994)That's when it's in a 25 fps comp or final file.

The thing is, when I set the Composition framerate to 99fps in After Effects, it looks fine, not choppy at all. So it's not the electric motor. But putting that 99 fps composition in a 25 fps composition doesn't help either.

I know this could be the "non-realistic" lacking of motion blur but I tried adding CC forced motion blur, I tried using frameblending, I even tried converting the MOV from the camera in MPEGstreamclip to a MotionJPEG encoded file first and then import it into After Effects. All doesn't work.

Any ideas get the final file less choppy? Any help greatly appreciated!


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Dave LaRonde
Re: Choppy shot when speeding up slider footage
on Mar 1, 2012 at 3:31:45 pm

There is so much not mentioned here that it's difficult to diagnose any actual problem you may be having with AE.

You're probably aware that ANY shot speeded up by a factor of 10 won't look natural without the motion blur created in-camera by shooting at the actual speed.

There are some other blurs in AE that may simulate the look you seek, and I suggest you play around with them. If none of them work, you may have to resort to a third-party plugin.

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


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Jerry Renes
Re: Choppy shot when speeding up slider footage
on Mar 1, 2012 at 3:35:48 pm

Hi Dave,

Thanks for your advice. The thing is, we also tested it with the slider running at normal speed, so the shot won't have to be speeded up. But this also gives the same weird choppy unrealistic look.

We also shot at different shutter speeds 1/80 and 1/250. But the only way we get it smooth is playing back the 99fps composition.

Any other ideas?


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Dave LaRonde
Re: Choppy shot when speeding up slider footage
on Mar 1, 2012 at 3:59:57 pm

Not really. 25fps is a pretty low frame rate, so you're probably seeing a phenomenon called judder, a function of both motion and frame rate. It's more pronounced at lower frame rates.

Motion picture photographers deal with it all the time, and the real pros have complicated formulae for overcoming it that they guard jealously... it's their meal ticket, y'know?

In which case, you have to play with the camera's rate of motion to get something that doesn't look bad.

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


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