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Partial Scene Green Screen Keying

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Jon Wooley
Partial Scene Green Screen Keying
on Jul 1, 2015 at 4:47:25 pm

Hello everyone,

I’m looking for any help I can get regarding the use of a "spot-greenscreen.” Basically, I’m looking to key out only a small section of my scene using a green screen. Then I replace the keyed out section with a continuation of the scene’s background (taken before the green screen is added to the shot) so that, ideally, the whole thing is seamless. From there I can add effects (text, small images, etc) and they will look like they are behind the subjects (who’s shoulders are in front of the green screen, like a news broadcast).

However, I’ve run into nothing but trouble when it comes to the edges of the green screen. After I apply Keylight (I’ve also tried any combination of Color Key, and Red Giant’s Primatte Keyer) there is a nasty dark boarder around my green screen which is otherwise invisible at this point.

So, the question is, does anyone know any tips on getting rid of that dark boarder? I’m relatively inexperienced when it comes to green screen keying, so even terms I could search or tutorials would be a huge help. Most everything I’ve found is for full screen keying rather than (for lack of a better term) spot keying.

Thank you.


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Dave LaRonde
Re: Partial Scene Green Screen Keying
on Jul 1, 2015 at 6:35:46 pm

On the chroma key shot, animate a mask to cut off the edges of the green screen. If the camera doesn't move, you probably wouldn't have to animate it.

You will be rid of the problem edge.

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


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Jon Wooley
Re: Partial Scene Green Screen Keying
on Jul 10, 2015 at 7:05:43 pm

Thanks for the response Dave! The problem I have is that the talent is constantly moving through the boarder as their arms and heads intersect the green screen quite often. If I understand what you are saying (and I may not), animating a mask for each of their crossings for a half hour show would prove excruciating.

Below is a screen shot of the issue I'm having. To the right of the talent there is a black line, that's what I'm looking to get rid of.


I can get it out by changing the Grow/Shrink parameter in Keylight to -6 but that thins the arms and faces of the talent too much when they enter into the affected area.

Here is the source for reference.


Thank you for all the help so far!


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Dave LaRonde
Re: Partial Scene Green Screen Keying
on Jul 12, 2015 at 4:27:55 pm

Having now seen the shot, you'll have to rotoscope the shot as well as key it. You'll have multiple layers. AE's Rotobrush tool can help a lot, but DO NOT expect to use it intuitively -- you can't Look up Rotobrush resources on the Adove web site for training.

No way around it, this is going to be painful and time-consuming because you didn't shoot the green screen properly. You can't easily separate the subject from the background. I truly hope you do a post-mortem when you're done to ynderstand you you could have shot it differently to make your life easier.

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


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Jon Wooley
Re: Partial Scene Green Screen Keying
on Jul 13, 2015 at 2:55:18 pm

[Dave LaRonde] "You can't easily separate the subject from the background. I truly hope you do a post-mortem when you're done to ynderstand you you could have shot it differently to make your life easier."

That's why I posted here. As I said in my first post, "I’m relatively inexperienced when it comes to green screen keying, so even terms I could search or tutorials would be a huge help."

The shot I posted was a test, you'll notice that the stand for the green screen is in the shot. You mention that I didn't shoot the green screen properly, I take that to mean that there is a way/technique that I could use to shoot the green screen the removes the black line issue entirely. Can you instruct me on how that is done? Or perhaps send me to a, or any number of, tutorials so that I can learn that technique?

Thank you.


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Stephen Smith
Re: Partial Scene Green Screen Keying
on Jul 15, 2015 at 3:17:27 pm

Typically when you shoot with a green screen you want it to fill the whole background and then you don't need to worry about stuff like this. The good news is that you can still make it work. We did a TV with a green screen that was only so big so I needed to do rotoscoping. Check out the spot here:



Here is the side by side so you can see the green screen:



Here is a tutorial on rotoscoping:

http://www.videocopilot.net/tutorials/alien_surface/

Best of luck.

Stephen Smith

Utah Video Productions

Check out my Vimeo page


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