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Keying everything moving in a lock shot

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Matthieu Laclau
Keying everything moving in a lock shot
on Jul 27, 2016 at 1:59:41 pm

Hi,

I'm starting working on a project where most footages are coming from surveillance cameras.
Most of the shots are locked, with people or car moving inside the frame.
I'd like to key everything that is moving. So then, I can add a effect on the moving object (like in the attached picture).
Wen the object stop moving, then it becomes normal.
I can use After Effects, but if it would be possible to do that in Premiere, it would be even better.
Any other app could be fine as well.
Best,

Matthieu.



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Ken Teutsch
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 2:38:45 pm

You can roto the silhouette, of course, but that's a pain...

But if you have a frame without the person in it to use as a clean plate, you could grab that frame, then use the Difference Matte effect to cut out the moving object and reveal a layer underneath with your red effect applied.


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Dave LaRonde
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 2:44:27 pm
Last Edited By Dave LaRonde on Jul 27, 2016 at 2:51:23 pm

If the edges on the completed keyed subject aren't too critical, AND you actually shot with something better than a surveillance camera, AE's Difference Key is probably your best bet. It looks at the footage, compares it to a recerence clean plate, and removes the difference.
It is CRITICAL to have a clean plate. If you don't have one, you have to build one.
It is CRITICAL to have a locked-down shot. Rock steady. If it moves enen a little it won't work.
Since it works by comparing a pixel in a given position to its counterpart on a reference image, you get the best results on the highest-quality, identically-exposed footage.

If the difference key doesn't work out, you probably have to rotoscope. You may have to animate some masks anyway to get it to work.

With all of this in mind, I wouldn't even dream of trying this in an editing application. Use AE.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Matthieu Laclau
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 2:53:11 pm

Ken and Dave,

Thanks for your fast answer. I'll try that.
It doesn't have to be very precise. It can look "dirty", so I guess using the clean plate and the difference matte should work. Hopefully, I might have clean plates on most of shots.
We're working on real surveillance camera footages and I'm editor of the film.
I just want to be able to make the effect approximately to see how it looks, during the editing.
It should be possible to do the same in Premiere I guess, right?

Matthieu.


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Ken Teutsch
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 2:58:05 pm

There is a difference matte effect in Premiere. I haven't used it in Premiere, but I assume it works more or less the same as the one in AE.


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Dave LaRonde
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 3:03:41 pm

NO! It will NOT be possible in PP! It's a pretty powerful application, but you'll hate yourself for wasting your time if you try it.

There are good reasons why people use AE. The shots you want definitely are poster children for using AE. You can try PP, but you'll regret it.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Matthieu Laclau
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 3:24:22 pm

Ok! I'll forget the idea of Premiere and will do in AE.


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Dave LaRonde
Re: Keying everything moving in a lock shot
on Jul 27, 2016 at 3:30:44 pm
Last Edited By Dave LaRonde on Jul 27, 2016 at 5:26:05 pm

Giving this shot further thought, and given that the footage is REAL surveillance cam footage -- i.e. NOISY -- be prepared for the following:
· Animated garbage masks to compensate for the inevitable holes due to the changing noise patterns in the footage compared to the clean plate
· Building edge and core mattes through a combination of the difference key and rotoscoping to create a completed matte of the subject.

You would have been a LOT better off if you had used the highest-quality footage possible. Think 4K, captured in ProRes. You would have had a much easier time pulling off these effects shots. It's really easy to make great footage look bad in AE, so you could easily have gotten the surveillance cam look back. Its really tough to make bad footage look good... and you have bad footage. Now you have random noise to battle, which will be a time-consuming, Right Royal Pain in the worst body part you can imagine.

You can get an indication of how to proceed by putting the layer to be keyed over the clean plate, then applying the Difference blend mode to the top layer. If there are variations between layers, they show up as shades of gray. Black will be totally transparent. Step through your shot frame-by-frame.

You might be pleasantly surprised, but considering the footage, I kind of doubt it.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Walter Soyka
Re: Keying everything moving in a lock shot
on Jul 28, 2016 at 1:42:29 pm

I would use Twixtor Pro to generate motion vectors from the shot, then create a matte from that.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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