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White Fringe Around Keyed Foreground.

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boojiprime

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  • Real Name: Brian Bruzzi

White Fringe Around Keyed Foreground.

PostTue Dec 05, 2023 1:12 am

Spent the last week learning Fusion and compositing to key this awful blue screen and HAIR... HAIR EVERYWHERE. The spill impression tools do not work well with blue screens, apparently, but I found a workaround using some color suppression with the HueCurves tool.

Now, onto my main problem. For the life of me, I can not get rid of this white fringe. I've tried the compositing mentor's advanced keying tutorial and VFX study's compositing course to get some sort of adaptive edge despill. I feel like an idiot and am ready to rip my hair out and set fire to something. I'm working in Linear as far as I know (based on VFX study's course).

Where am I going wrong here? Let me have it. Don't hold back. I need to get this done for a client ASAP. Thanks in advance...

Image linked below:

https://drive.google.com/file/d/171nttw ... hV6oo/view

https://drive.google.com/file/d/1vfVBXs ... Alxcs/view

https://drive.google.com/file/d/11yx4oG ... yBLTf/view
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Hendrik Proosa

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Re: White Fringe Around Keyed Foreground.

PostTue Dec 05, 2023 7:05 am

That fringe is the result of foreground color mixing with the light background blue. Even if your key were perfect, it would be there, as in semitransparent areas alpha can't disassociate that mix. To get rid of it you have basically two approaches (use both as applicable), one of which you seem to have tried:
1) manipulate the edge color to turn it into what it should be;
2) extend the colors from inner areas (solid, where fg isn't mixed with bg) over that region.

There are many ways for doing the edge extensions, simplest of them is to erode in the alpha, apply it to the fg (premult fg with alpha), blur the result and unpremult. Then merge fg over that again using eroded and softened alpha and in the end apply the original best keyed alpha you have to that compound. Idea is to replace the color in that semitransparent region with the extended color from fg core so it kills the spill. Problem is that it doesn't work that well when you have different colors intersecting on the fg, so you need to fix some areas with masks.

To me it looks like your key is too hard too, edge seems quite sharp.
I do stuff.
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Sam Steti

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Re: White Fringe Around Keyed Foreground.

PostTue Dec 05, 2023 5:21 pm

Hey

Don't set anything on fire man, except if it's barbecue time in your area :)

Well, looking at your screen shot, I can indeed see the "classic" fringe around... Chewbacca ? ;) :D

There are indeed a lot of tricks to fix it; you may indeed select him in HSL color ranges for a better selection, first dilate a bit and then erode just after to get rid of semi-transparent pixels etc etc...

But here, why not merge the FG and BG in a Darken or Minimum mode BEFORE the key ? This would fill its hair with the right pixels in the first place...
All I found for you is the good old - but still very relevant - Damian making it here : https://moviola.com/courses/sky-replace ... g-the-sky/ (go straight to around 03:00)...

And while you're into it and since you're ok to watch videos on the topic (like Bernd's channel), why not recalling some of the foundations
https://moviola.com/courses/keying-greenscreen/

Good luck anyway, it looks like you're not far from your goal ;)
Last edited by Sam Steti on Thu Dec 07, 2023 10:33 am, edited 1 time in total.
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Olivier MATHIEU

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Re: White Fringe Around Keyed Foreground.

PostThu Dec 07, 2023 6:55 am

Nice links
Thanks
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