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Green screen too dark?

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Aaron Cadieux
Green screen too dark?
on Sep 7, 2011 at 4:38:24 pm

Hey Everyone,

I shoot green screen stuff pretty regularly. However, I shot some stuff yesterday that is not cooperating in post. I can't seem to get a clean key out of it. Unfortunately, we shoot MiniDV, and because I've been able to make MiniDV work in the past, we didn't think we'd need to rent something that shoots with a better color sampling ratio.

Here is a link to the raw footage.






I think the green is pretty evenly lit, but I think it's too low on the IRE scale. Prior to having these two gentlemen on set, we shot an African American officer against that same green screen. However, because of his darker skin, I had to open up my iris a little bit. I usually expose faces at around 70 IRE. The raw footage of the African American officer keyed pretty easily. I think opening up my iris to adjust for the officer's skin brought up the levels on the green screen just enough to make it work.

But when it comes to the footage of the two white officers, I must have closed down my iris too much. I've tried all of the color correction tools in AE, including Keylight. I've also tried Adobe Ultra. No matter what I try to use, the key on the two officers looks like crap. Am I looking at a re-shoot, or can I fix this footage in post?

Best regards, and thanks for your help.

Aaron Cadieux



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Aaron Cadieux
Re: Green screen too dark?
on Sep 7, 2011 at 5:17:53 pm

Hey Guys,

Here is an update to my own post. I tinkered all morning with different settings and different ideas to get this key to look halfway respectable.

Here is a link to a quick shot of a test result.






What I ended up doing was a long drawn-out process. I ended up splitting the video keying each officer separately. Oddly enough, the officer on the left was keyed using the "Chromakey" effect in Premiere CS3. For some reason, that gave me the best results for that officer. The officer on the right did not respond as well to the "Chromakey" effect. The officer on the right was exported from Premiere as a Quicktime file with an alpha channel. I brought it into AE and applied multiple "Color Range" effects until all of the green was gone. I finished him off with a "spill supressor" effect to drown-out any leftover green. I will end up needing to apply some spill supression to the officer on the left as well.

So these were the best results I've gotten so far.

-Aaron



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Aaron Cadieux
Re: Green screen too dark?
on Sep 7, 2011 at 5:19:16 pm

By the way. The blue background is temporary.



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Todd Terry
Re: Green screen too dark?
on Sep 7, 2011 at 5:52:27 pm

Yeah, the greenscreen looks a bit dark, but it's probably still doable.

Since you have After Effects, I would suggest doing your keying in AE with Keylight rather than doing the key in CS3. You'll get much better composites with Keylight in After Effects than you'll ever get with Premiere's internal chromakeyer.

We've had great results with Keylight. I'd say in many cases it's almost as good as Ultimatte or other super high-end keyers.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Steve Kownacki
Re: Green screen too dark?
on Sep 8, 2011 at 12:31:23 pm

Those guys are pretty stoic. You can get a garbage matte really close to them so you're only worrying about keying a very minute outline, not the entire background. I'd also cut them into layers/individuals and key them separately like you did.

Steve






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Mark Suszko
Re: Green screen too dark?
on Sep 8, 2011 at 4:07:19 pm

Dude, he's WEARING A GREEN UNIFORM. This is when you switch to blue.

Also, you can see from the first sample that the left side green is much brighter than the right side green. That's not evenly-lit enough. have you tried cutting a luma Key from this?

I would likely use a couple iterations of the 8-point garbage masking tool on this. Also apply a little shadow on the key channel to help mask the aliasing. You might also consider transferrign the DV footage into another codec to work from; I find this helps me alot with the standard FCP keyer.

One other idea that I use sometimes: You can export a frame movie or stack of stills into a folder, and in photoshop, apply a batch action to quickly automate the rotoscoping of the subjects one frame at a time. It sounds tedious but the batch action speeds it up a LOT. If nothing else, you can use the batch actions to do additional color-correction and filtering and aliasing-reduction. Then the folder just re-imports into your timeline and you are good to go.


As far as the dark-complected guy keying somehow "better", that really shouldn't be because of his skin color. Rich Harrington has a very cool tutorial on color correction right here on the COW that shows you, flesh tone still reads as flesh, no matter your ethnicity, because it's based on the red blood just under the skin, not the pigment. You should check it out.


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Aaron Cadieux
Re: Green screen too dark?
on Sep 8, 2011 at 7:27:30 pm

Mark,

Thanks for your help. I think the cop with the dark complexion looking better had more to do with my f-stop and less to do with his skin color. I opened the iris to get a brighter exposer on his face, which in turn slightly increased the exposure of the entire image (including the BG). I think that extra exposure made keying his footage a little easier. But I will definately check out that tutorial. Thanks again.

-Aaron



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