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How to key out a background object that people walk in front of?

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Erin Herbst
How to key out a background object that people walk in front of?
on Mar 20, 2018 at 4:15:52 am

Hi everyone! I'm still getting my bearing with AfterEffects, but have a recent project working on a YouTube series requiring green screen. When we filmed this, the director insisted that we have an easel and a bookshelf in the background, however there is so much spill on them that it looks like crap in the final key:






I would love to just matte out these two objects, but because the actors walk in front of the objects at the start of and in the middle of the scene, I can't figure out how to do this without their limbs disappearing when they enter the masked area.

So for the newbie here, can someone explain how I would go about matting out these two objects without matting out my actors when they move?

Much appreciation.

Erin


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Steve Bentley
Re: How to key out a background object that people walk in front of?
on Mar 20, 2018 at 6:10:53 am

Based on the footage I'm not really understanding the problem.
Use two layers in AE - one for the bookshelf and the easel and just draw a mask around them (it seems its a locked off shot so that should be a still mask). Inother words you are going to mask these objects so they show up in the comp, don't try and get rid of them.
Then do your key for the people on a second layer.
If you apply the same color correction effects to both of these layers, even though the matte of the easel etc will be horrible in the layer with the people keyed properly, the masked layers of the easel will fill in all the transparent bits. (people go on top of masked easel layer).
You don't have to do your green spill correction in the keyer effect, you can apply any color correction and spill killer to an adjustment layer that sits over top of both the people and the masked easel layer. Then both of these layers get precomped and that precomp goes over your background. I would stick a background into the precomp just to work with for reference when adjusting your color correct and then turn that background off. Thay way you aren't looking at the final and popping into tweak colors, looking at the final, popping in to tweak colors over and over.



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Erin Herbst
Re: How to key out a background object that people walk in front of?
on Mar 20, 2018 at 12:09:40 pm

Hey Steve, thank you so much! Appreciate the detail and fairly simple answer ☺

Erin


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Mark Suszko
Re: How to key out a background object that people walk in front of?
on Mar 21, 2018 at 8:39:10 pm

Butting in with a probably useless two cents, and AE is not my forte', but the problem I see in your comp is: nothing's got a shadow, or a reflection, so everything and everyone looks like it's floating, pasted on and not really "grounded" on the backdrop. If you just add a soft shadow to the existing elements, warped to lay on the floor and softened with Gaussian blur, they will immediately seem more realistic in the comp. Adding some light wrap on the sides facing key light sources will further enhance the effect's realism.


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Steve Bentley
Re: How to key out a background object that people walk in front of?
on Mar 21, 2018 at 10:41:27 pm

Good point Mark. shadows really ground people in an environment and really make them appear to be "there". The brain also uses shadows to determine volume so it makes them seem less like cardboard cutouts in a keyed shot.
You can use the Videocopilot VCreflect tool (I think its free) to do shadows for vertical people on an angled plane - we find its the most intuitive way to do fake shadows especially for when their feet move and lift. You could also put a 3D plane in there and light the keyed "cards" with a back light to cast a shadow but that has its own headaches.



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