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Garbage Mattes and Keys

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Michael Cummins
Garbage Mattes and Keys
on Sep 24, 2008 at 3:28:15 pm

I've got a sequence from FCP6 that I've brought into Motion 3. It involves an individual against a mostly white background, fairly evenly lit. We've had success with using luminance keys in the past, replacing the background with a white color solid.

This time, however, there's an emblem on his shirt that is white as well, which the luminance key picks up. My intent was to simply motion track this emblem and apply a small garbage matte around it to prevent the key from touching it. It's been about an hour of frustration, and another hour of searching for existing threads similar to this.

I've always been primarily and AVID Xpress Pro user, and the technique of garbage mattes applied to a key in this manner has always been old hat. Is there a way to effectively do this in Motion 3?

Or even AE CS3? I usually use it for keying and the like, but the integration and ability to import Motion projects into FCP is going to save a good couple days' worth of work.



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Noah Kadner
Re: Garbage Mattes and Keys
on Sep 24, 2008 at 4:33:40 pm

Garbage mattes are easy in Motion. You can draw a bezier or b-spline and then turn on auto-keyframe and step forward frame by frame to adjust size and position and shape. You can also feather it out to fit. I can usually do any shot in 5 minutes this way.

Noah

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Michael Cummins
Re: Garbage Mattes and Keys
on Sep 24, 2008 at 4:43:08 pm

I've got garbage mattes down; they're easy. It's applying the garbage matte to the luma key ONLY. So far, I'm ending up with a whole in the talent's chest because the matte is applying to the image, and not just the key.



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Michael Cummins
Re: Garbage Mattes and Keys
on Sep 24, 2008 at 5:17:56 pm

I've found a fix that seems to work just fine. Just needed a little "out-of-the-box" thinking.

I duplicated the image, garbage matted the problem spot, and applied the Match Move behavior to my analyzed motion. This moves a garbage matte revealing only the needed portion of the original image directly over the keyed image. Seamless.

If you know of other fixes/ideas, let me know. But for now I think I'm good.



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Jeff Asher
Re: Garbage Mattes and Keys
on Sep 26, 2008 at 9:59:56 pm

Someone correct me if I'm wrong but that is how you'd normally do an effect like that. No addition "fix" necessary.



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Larry Asbell
Re: Garbage Mattes and Keys
on Sep 27, 2008 at 9:08:19 pm

Michael, I'm glad you asked this because I was recently banging my head against a similar problem:

How do you mask the area of an image that a filter is to apply to? (Think animating a glow across an object.) My testing and reading between the lines of the Motion 3 manual seems to say that you also have to duplicate the original layer also.

Boris and AE both allow you to mask a filter directly so I wasn't expecting this.

In the Motion 3 manual your situation of needing to mask a key is discussed for several pages in the Motion 3 manual starting on page 1108.

But the general question of masking a filter, something you need to do for many common effects, is discussed only obliquely as far as I see. Not only for animating a glow across an object, but applying a blob of blur/mosaic to block a face, or color treating just an area of a picture. The section on Applying a Filter to a Mask on page 1000 is not the same as applying a mask to a filter. In other words, I don't want to add a ripple edge to the creature's cut-out eye, I want to apply my filter to the eye and see the rest of the face normally. This need and the fact that you must duplicate the original layer is not mentioned.

Once I got clear on the solution, the only efficiency I could bring to the method is:

Rather than duplicate the layer, clone it so it automatically keeps the clone updated as you modify the original layer.





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