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undoing overcranked footage

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Antony Christie
undoing overcranked footage
on May 1, 2009 at 7:51:34 pm

I'm a student trying to understand overcranking and hope someone could answer just this one simple question for me, beleive me, I'm not lazy, just got a million & 1 other things 2 do & I'm working 2 a tight deadline...

I have some footage recorded on an ex1 overcranked to 60fps - I'm in the UK so edit for PAL - and I'd now like a couple of the overcranked shots to play back at normal speed.

If I delete 3 out of every 4 frames will my footage play at normal speed as good as if I shot 720p footage at normal speed in the first place?

Many thanks,
Antony


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Craig Seeman
Re: undoing overcranked footage
on May 1, 2009 at 8:48:37 pm

My quick answer would be try
speed up in timeline
Optical Flow

Without details as to time base targeted (25fps or maybe 24fps for "international" use?) and what tools you have it's hard to make any concrete suggestions.

I'd opt for the above two rather than tediously deleting frames unless you have a fair amount of time on your hands.



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Antony Christie
Re: undoing overcranked footage
on May 1, 2009 at 9:16:04 pm

Hi Craig

& thanks for your speedy reply!!!

I'm making a 5 second Ident and will need to rotoscope (using Difference Matte) around a running guy in each frame; the reason I borrowed an ex1 and shot in S&Q Motion in the 1st place (instead of shooting with my Z5 and slowing in post).

The footage is great; lovely still frames! However, I'd really like the running to start normal speed and then slow down.

My understanding of what the ex1 does when it records slow mo is that it records 4 times as fast, therefore I hoped that if I remove/delete 3 of every 4 frames, I would end up with footage that played at normal speed, or is that just wishful thinking?

A


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Craig Seeman
Re: undoing overcranked footage
on May 1, 2009 at 10:01:52 pm

I understand the challenge you face now.

I'd try using a good optical flow filter first but there may be some tweaking involve and not all optical flow filters are equal. You could try it in Apple Motion if you have or maybe Apple Shake would be better. Alternately there's Twixtor.

Others here might have different tools to suggest.

The challenge though is that there may be "motion blur" type issues depending on how the optical flow filter creates the new (or removes the) frames that might make rotoscope difficult.

If the edges in the objects have too much motion blur then you may find better results with just removing frames but that's going to be a problem if you want a smooth, rather than sudden, speed change.

If you shot with a fast shutter you might have an easier time of it so I'm hopping you did that.



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Rafael Amador
Re: undoing overcranked footage
on May 2, 2009 at 3:01:51 am

If you are in FC, just speed the clip up and uncheck "Blend frames'.
FCwill just discharge frames.
[Antony Christie] "My understanding of what the ex1 does when it records slow mo is that it records 4 times as fast, therefore I hoped that if I remove/delete 3 of every 4 frames,"
No really 4x.
Depends of of the time-base you had when shooting (24, 25, 30,..0 and how much you had overcranked.
You need to make few numbers to see how much you must spped up the film now.
But in any case there in not a 4x.
The higher speed when overcranking would be when shooting p24/60. And this would be 2.5x.
rafael


http://www.nagavideo.com


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Antony Christie
Re: undoing overcranked footage
on May 1, 2009 at 9:23:06 pm

PS. (Sorry; now I understand) time base targeted: 25fps captured at 60fps

A


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Rafael Amador
Re: undoing overcranked footage
on May 2, 2009 at 6:11:49 am

So you need to speed up your footage a 240%.
rafael

http://www.nagavideo.com


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Craig Seeman
Re: undoing overcranked footage
on May 2, 2009 at 6:36:32 am

[Antony Christie] "The footage is great; lovely still frames! However, I'd really like the running to start normal speed and then slow down. "

But he wants to vary the speed so he may need to use optical flow unless the slow down will be sudden.



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Antony Christie
Re: undoing overcranked footage
on May 4, 2009 at 4:51:01 pm

Thanks for all your help you guy's!

In actual fact I wanted to do both (speed a whole clip and speed the beginning of a clip).

I am using Avid MC3 & After Effects - I'm not quite there yet but used FluidMotion to adjust speed without noticable change in the individual frame quality. I had shot it with shutter speed 1/125 which I'm sure helped.


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Antony Christie
Re: undoing overcranked footage
on May 29, 2009 at 12:49:58 am

Thanks 4 your help on the EX1 FCP post - invaluble!!!!

Here r links 2 this AE project in case you're interested 2 c how they turned out:

http://www.antonychristie.com/CIA Ident 1 - 1080i.avi

http://www.antonychristie.com/CIA Ident 2 - 720p.avi


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