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Use Choker or Refine hard matte to clean up noisiness in Difference Matte?

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Andy Zou
Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 3:53:35 pm
Last Edited By Andy Zou on Aug 3, 2016 at 3:54:28 pm

Hey y'all, here's the pic that's all the explanation you probably need:
http://i.imgur.com/SBd64sJ.jpg

Currently in Premiere, but Will go to AE and add refine matte or choker there (is that silly? Should I have gone to AE from the first place? I just find I work a little quicker with the layer system et al in premiere, and there might be some frame-sized edits)

As you can see, each successive difference matte puts noise onto the layer beneath. (Suit character puts noise on the blue shirts, dark blue puts noise onto the light blue) Turning Matching Softness up will reduce the noise of the topmost layer, but start introducing transparency in the skin tones.

I'm wondering what the best tool is to reduce the noise on the layers beneath (the blue shirts) without compromising the matte of the foreground character. A tool that takes small-area splotches and reduces them, while expanding the spots that should be opaque?

For the rough I have been just doing a mask around the characters, and will probably do that when they don't overlap. But when they do, what is the suggested tool?


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Dave LaRonde
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 4:28:09 pm
Last Edited By Dave LaRonde on Aug 3, 2016 at 4:32:54 pm

Why are you using the Difference Matte? Just curious. It's about the WORST way to separate the subject from the background in AE. Too many things can go wrong.

But to fix the white line seen in your screen shot, I think I'd try Refine Matte before I'd go to the Matte Choker.

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


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Andy Zou
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 5:05:48 pm

If I had had more time, or have known how difficult the difference matte would be, I would have just moved a green screen around for every set up. But I didn't, so this is what I have to deal with. Every shot has a plate without any actors in it.

For the hard white line around the character in the suit, I will use refine matet, yes, but is there a recommendation for the noise that that first layer is putting on to the other characters in the background?


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Andy Zou
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 5:18:26 pm

Looking at the screenshot now on my phone I see that the noise is a lot harder to make out in a small still frame, but in motion on a larger screen there's some noisiness on the back two characters.

Capture was in 4k, export will be 1080.


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Dave LaRonde
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 5:24:06 pm

For diagnostic purposes it would be helpful to see a screen shot of the comp you used to take the original screen shot.

I'm thinking you wouldn't have to do ANYTHING to the bottom-most layer. They're actors over the background, right? Why mess with any keying? You can use a precomp to put the actor on the top layer and the empty background layer together, use the Difference Matte, fix the white line and you're pretty much done.

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


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Andy Zou
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 5:38:37 pm

Hey Dave, thanks.

I'm definitely not applying anything to the lowest layer (the light blue shirt). I'm away from editing rig right now, but I can tell you the layers are like this:

1. Suit.
2. Dark Blue.
3. Light Blue.
4. Plate.

Light Blue has no effects applied, Suit and Dark Blue have Difference Matte applied using the Plate.

The white line I believe I know how to fix easily as you said with the Refine Matte. What I am less knowledgeable on how to properly fix is that after using the Difference matte on Suit, there is noisiness that is most apparent on Dark Blue's shirt, and to a lesser extent, Dark Blue puts noise onto Light Blue. I can matte out some of it tediously, but I am wondering if there is a better tool for the noise.


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Dave LaRonde
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 6:37:11 pm

The noise is a by-product of the Difference Matte. If you've done all you can to clean it up, you may have so resort to rotoscoping. Sorry.

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


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Walter Soyka
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 3, 2016 at 7:20:44 pm

Yes, you can eliminate all that tiny detail noise plus a lot of the fringe with either effect.

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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Andy Zou
Re: Use Choker or Refine hard matte to clean up noisiness in Difference Matte?
on Aug 20, 2016 at 5:03:39 am

Here's the final product! Hope you enjoy!







Had a solid time learning more about the limitations of the difference Matte as well as how to use the Refine Hard Matte and Matte Choker. Also even found uses for Mask Expansion, which I never really thought of a good use for until I was selectively masking problem edges but needed to have a manual "inside mask."


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