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chroma key artifacts

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Kelly Schaeferchroma key artifacts
by on Sep 12, 2014 at 2:37:19 pm

Hi All, thanks for the responses to my question about multiple keys. I have another problem with the same video. I've attached a link. What can I do to fix the crawlers and artifacts around the area where the left and center figures touch? I keyed out the blue screen using 8 Bit Digital TV's process which works beautifully. But this time I have this issue. Any responses appreciated!


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Chris OlsenRe: chroma key artifacts
by on Sep 12, 2014 at 7:58:51 pm

Hi Kelly,

I'm not familiar with 8-Bit's process, but I'll assume you're using Keylight (and even if you're not, any keyer worth its salt will have similar controls, and this advice ought to help).

In a case like this, with a lot of flyaway hair and detail, I like to use the Alpha view to see what exactly I'm keying. You'll probably want a little semi-transparency around the hair, so I'd navigate to a good reference frame (where the issue is manifesting itself), and adjust the Clip White until the hair is a faint grey.

You can also increase the Despot Black by a very minor amount (maybe 2?) and that will sort of 'glue' the key together in those areas where the hair seems to break off.

I'd also say using Screen Pre-Blur instead of Screen Softness will likely serve you better here... Can't say for sure without seeing your project, though.

In conclusion: Semi-transparency, clip white, despot black, view the alpha. Hope this helps!

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Chris WrightRe: chroma key artifacts
by on Sep 12, 2014 at 8:13:24 pm

It's a last resort because it takes longer, but AE's rotobrush has anti-boiling features. read up how to use it, it's a little different than masks. You can also get done a lot faster by using junk mattes just before rotobrush.

The hair needs transparency and color spill replacement. If you want better results,try Primatte and Ultimatte, if not, I'd recommend creating your own lightwraps, transparencies, or soft edges precomps to soften the pixel edges. channel blurs, median blurs, matte chokers can also help.

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Kelly SchaeferRe: chroma key artifacts
by on Oct 2, 2014 at 7:49:49 pm

Hi all, I swore I replied to this thread, but still learning the forum. Above is a link to my solution for the hair transparency and squiggly edges. It took a few days research and a few days to work through, but for a first attempt I'm ok with it. Now to replicate before I forget how, and expand from there. Any comments appreciated.


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