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Stabilizing a shot to another shots stabilization

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Spencer Katz
Stabilizing a shot to another shots stabilization
on Jun 6, 2015 at 6:08:47 am

Hi everyone,

I can't post the footage because of my client, but I think I'm wording this right. I have a dolly shot down a hallway, I tracked the scale/position and applied it to a null. I have another dolly shot down the same hallway with a different character, it's almost exactly the same in speed and alignment but not 100%. I tracked the scale/position of the second take and applied it to a null as well.

At the first frame, the two square boxes from the nulls line up almost exactly, but as the shot progresses they drift. These two nulls need to be aligned on top of each other to stabilize take 2 to take 1, but I can't figure out how to do that.

Or is it somehow possible to use the 3d camera tracker to analyze both takes and then lock the track points together (because nothing is different but a character in the center of the hallway, and the alignment slightly, so all the same track points are visible.)

I'm a bit of a novice, but any help would be great, thank you!


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John Cuevas
Re: Stabilizing a shot to another shots stabilization
on Jun 8, 2015 at 1:02:41 pm

If I read it correctly, you should parent the 2nd Null to the first null.

Johnny Cuevas, Editor
Thinkck.com

"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.


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Spencer Katz
Re: Stabilizing a shot to another shots stabilization
on Jun 8, 2015 at 3:56:10 pm

Unfortunately, nothing happened. At this stage, I don't have the tracker properties applied to the clips, just their null objects. One thing that works a little is to apply the stabilization to the clips (which zooms them way out during the dolly shot), then activate 3D on the clips and create a new camera, and parent that camera to one of the takes.

This syncs things up I think, but because of the stabilization there's a drift that has to be corrected every 12 or so frames.

Thanks though, any other ideas on how to possibly lock the same moving point from two extremely similar camera moves?


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Blaise Douros
Re: Stabilizing a shot to another shots stabilization
on Jun 8, 2015 at 4:29:56 pm

You'll need to rotoscope the 2nd character out of his shot, and composite him into the first one. There's just no way that you will get the two hallways to match up if it was shot without electronic motion control. This may allow you to get away without doing too much keyframing to match the shots, as differences on the individual character may be less noticeable than the whole hallway.

If you don't know how to use the Rotobrush, do a quick Google search--it's a powerful, easy-to-use tool, but not super intuitive.


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Spencer Katz
Re: Stabilizing a shot to another shots stabilization
on Jun 8, 2015 at 4:41:44 pm

Thanks, this is actually a stop motion project. An extended steel bar held the camera which was nudged along a track with a ruler. The actual differences in the two takes are less than 1mm, so that's why I think there might be a way to lock them together. Each character has additional frames with green cards inserted to get a key, so I'm easily able to cutout the character, but then aligning it to the master background pass is the problem.

Thanks again, I'll look up more about the rotobrush!


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Blaise Douros
Re: Stabilizing a shot to another shots stabilization
on Jun 9, 2015 at 3:48:39 pm

Yeah, I think roto is going to be the trick here. One of the other things that After Effects' tracker is capable of is tracking position, rotation, and scale. If you track the scaling of character one, and then apply that scaling to a tracked, stabilized, and rotoscoped character two, you should be golden.


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