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ChromaKey bleed-through after render

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Michael Moser
ChromaKey bleed-through after render
on Jan 24, 2014 at 8:00:45 pm

Hi-
I'm using the FCP7 Chromakey effect and I've got a great key from a properly lit source and green screen...
Except, I'm getting a little bit of annoying bleed-through as intermittent scan lines on a dark grey-blue jacket. Before render, it looks like I've taken care of it by incrementally changing the key on luminance width and bringing down the set up -.1 or -.2 from the original using the proc amp effect, but after it's rendered the lines re-appear...
Any suggestions?
Thanks,
Michael Moser


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Mark Suszko
Re: ChromaKey bleed-through after render
on Jan 24, 2014 at 9:10:41 pm

Is this really keying off the jacket color, or moire' effect from a pattern on the jacket?

You could add a mask layer in the key in the are of the problem in the jacket.

if you have FCP7, you should have the Primatte RT keyer available: it is superior to the Apple keyer.


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Michael Moser
Re: ChromaKey bleed-through after render
on Jan 24, 2014 at 10:07:00 pm

Both good ideas...Thanks.
I also reduced the background video level. I'll keep futzing with it.

What I'm concerned with is that each change seems to work fine before the render, but then the problem reappears after the render and is slightly worse when I output it as a Quicktime .mov to be used as an element. I try to play it close to the edge level-wise to achieve a realistic key, but it seems the black and video levels change during render and output thereby exacerbating any little problems.

I'll try both solutions to see where I get.

I've got Keylight, also, which I can play with, but I'm trying to see how these levels change and interact with each other as I make the incremental changes.
Mike



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Mark Suszko
Re: ChromaKey bleed-through after render
on Jan 24, 2014 at 11:28:37 pm

If it looks good but then re-appears after rendering-out, maybe it's not the key but that you are transcoding to a wrong codec setting?


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Michael Moser
Re: ChromaKey bleed-through after render
on Jan 26, 2014 at 12:21:13 am

By the way- There was no problem with moire on the jacket...but totally independent of the chroma-key issue--the tie did cause a problem; and it wasn't because of the pattern, but the weave of the tie which was very reflective and moire-ing like crazy...not visible, by the way, on the production monitor at the shoot.

It was particularly bad on the knot of the tie. I layered a little square over the knot with a touch of gaussian blur which hid the moire.

....All this to make it look like a guy was sitting in front of a window.
It's amazing the hoops we jump through to make it look like no hoops were jumped.



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jerry wise
Re: ChromaKey bleed-through after render
on Jan 24, 2014 at 11:01:21 pm

are you trying to chroma key an h264 source?


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Michael Moser
Re: ChromaKey bleed-through after render
on Jan 25, 2014 at 12:23:47 am

I'm starting with XDCam MPEG 4:2:2 (a Sony F55) and transcoding to ProRes HQ on the render. Green screen evenly lit, so it has to do with the key settings, I think.



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Dave LaRonde
Re: ChromaKey bleed-through after render
on Jan 25, 2014 at 12:44:14 am

If you have a spare moment, try transcoding a shot XDCAM clip to ProRes, import the clip into FCP, key it, export it and see how it looks.

I'm not sold on using ANY kind of mpeg for chroma keying.

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


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Michael Moser
Re: ChromaKey bleed-through after render
on Jan 25, 2014 at 12:56:33 am

I'll try that...
Never has been a problem in the past and I had been working with material from the PMW-350 and the F3 which are 4:2:0.
I originally was double recording to a KiPro for that reason, but since I was able to pull a good key before, I stopped using it.



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Dave LaRonde
Re: ChromaKey bleed-through after render
on Jan 25, 2014 at 1:07:16 am

Ah, wouldn't that be because the KiPro is able to directly to ProRes, no mpeg necessary?

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


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Michael Moser
Re: ChromaKey bleed-through after render
on Jan 25, 2014 at 4:19:40 pm

That's right. The KiPro records 4:2:2 from the SDI port as ProRes.
What I've ended up doing, in this case is matte-ing out the background behind the subject using the 8 pt garbage matte inverted...That seems to have solved the problem for the moment, though I still need to QC it on a larger monitor.
I'm going to try the other solutions though to see where the problem lies...
Michael Moser



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