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Old December 22nd, 2008, 04:13 PM   #1
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Help needed with a timewarp effect please!

Hi!

after watching at the revolve 2008 movie (it's a kitesurfing movie featuring aaron hadlow) I was wondering how one of the many effects applied to that movie is created:
1) the kiteusrfer is moving normally in the water with some people moving on the beach on the background
2) he jumps and all suddenly during the jump the speciall effect is applied: he slows down to about 50% of the speed while all the rest including the backround keeps going at the normal speed.

I am really wondering how this effect is created!

Thanks! :)
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Old December 22nd, 2008, 07:22 PM   #2
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You can apply a keyframe in the effect at the frame where you want the rate to change. 100% before the keyframe, 50% after.

If you're editing in Premier Pro CS3 or later, the Time Remapping feature will do the same thing the same way and there's no reason to jump to another application so you save time.
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Old December 23rd, 2008, 12:12 AM   #3
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Hi Tripp,

thanks for your reply! yes I use to use premiere CS3 but even AE.
I'm not an expert at appling advanced effects like this one.
May you explain me in a more detailed way how to proceed?

Since the only thing that slow down at 50% of the speed is the subject jumping while the whole rest of the scene keeps going at the normal speed, should I cut him?
But since the camera is moving, wouldn't this create a black hole behind him while he slows down?

Thanks for your help!!
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Old December 23rd, 2008, 01:44 AM   #4
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I would like to add that the camera was moving. It was not a steady camera...
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Old December 23rd, 2008, 01:54 AM   #5
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ok I ahev found a youtube video of a kiteusrfer that have the same effect:
YouTube - Flexifoil Aaron Hadlow Pro Hadlowpro Kiteboarding Kitesurf

starting from 0:55 you can see the effect I am talking about.
The kiteusrfer going slow motion and the backgroudmoving normally.

Thanks for your help!!
:)
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Old December 23rd, 2008, 06:10 AM   #6
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Quote:
Originally Posted by Stefano Mastik View Post
Since the only thing that slow down at 50% of the speed is the subject jumping while the whole rest of the scene keeps going at the normal speed, should I cut him?
But since the camera is moving, wouldn't this create a black hole behind him while he slows down?
Yes it would, if I understand you correctly. One way this would work is to composite the rider from one shot onto a background in separate footage. You could use the same footage for both layers but it would take a lot of rotoscoping.

If you are interested in how to slow down the whole clip, there is a good tutorial on Time Remapping in Premier Pro here: http://www.adobe.com/designcenter/video_workshop/

I cannot link directly to the video, but you can get there by selecting Premier Pro CS3 in the top left box. Then click the "New Features" link in the top right box. The link "Variable Speed Changes and Time Remapping..." in the bottom box will take you to the video.
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Old December 23rd, 2008, 09:00 AM   #7
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Tripp thanks a lot for all your help.

But more then slowing down the whole clip I am really looking for slowing down only the foreground subject.

Maybe then the only way is to have 2 separates footages? But even this would create some other problems like for example the backgroudn not matching the foreground... I really wonder how they did it...
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Old December 23rd, 2008, 08:37 PM   #8
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At 0:55 in that clip there are definitely two separate layers for foreground and background composited together - maybe chroma-keyed out the sky on the foreground clip?

At 2:23 there's an interesting Matrix-like 'bullet-time' effect that has been discussed previously on DVinfo (I think) - I vaguely recall someone suggesting that shot involved multiple cameras, morph targets, and something like Twixtor.
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Old December 23rd, 2008, 10:59 PM   #9
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Oops. Should have watched the clip before I posted. My bad. The first time point that Graham mentioned is definitely composited. Two layers. That can be done in PP or AE, but probably easier in AE. The second time point, as best I can figure, was done by magic elves. (grin) You've now gone way past my skill set and I will step aside and let those with real brains chime in.
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Old December 23rd, 2008, 11:20 PM   #10
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Graham, Tripp, thanks a lot for your help.

I am mostly searching how to recreate the effect at 0:55 (maybe a tutorial?) as I have been told that that involves only one camera.
I know how to merge 2 layers if the background is not moving and there are no changes in it.

but in this case the background keeps changing over and over again (water, sky and so on).
So I really have no idea how to recreate it..
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Old December 24th, 2008, 01:13 AM   #11
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Stefano, The basic procedure is:

1) Film the dude as he kites along = clip A
2) Once he has passed, swing back and film approximately the scene again, except pan at about half the speed you did the first time = clip B
3) Import both clips into your editor, with A above B.
4) Reduce the speed of A by 50% - the two clips should now be about the same length (because you panned more slowly the 2nd time).
5) Mask out the background of clip A; once you've done this clip B will appear in the background.
6) Render.

The tricky bit is of course the masking, since it would be a big job to do by hand. However the clip you referred to had a fairly crude mask - my guess is they used some sort of chromakey that took out the blue sky and blue sea, and left behind the dark kiter and the white spray. With tweaks and garbage matts etc to tidy it up. But that's a guess....
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Old December 27th, 2008, 10:42 AM   #12
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The footage your asking about was done with at least two layers... the foreground layer and the background layer... both running at different speeds...

here is a very simple tutorial that should help you with this approach using Premier...

Digital Juice Support - Tutorials - Editor's Toolkit: Using Overlay Mattes with Adobe® Premiere®

Here is another one using AE...

http://www.eventdv.net/Articles/News...ects-37815.htm
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Old December 31st, 2008, 07:03 AM   #13
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Stefano,

As stated before this is obviously two layers... the clip starts at 0:51, there is no second guy in the background. At 0:55, when the slo-mo starts, he magically appears out of the foam.

I'd check out videocopilot.net, there are lots of good tutorials on compositing, rotoscoping, background extraction, etc. All geared towards AE.

Mark
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