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Old November 2nd, 2009, 12:45 PM   #1
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Green Screen Issues:

Hello,

I have a green screen and the few times I have used it, I noticed some of the green reflects back on to the person. This obviously creates issues when using chroma key in Premiere Pro (or any other program).

The people are standing on part of the green screen so maybe I should have the green screen only in the background? Any ideas would be appreciated.

Thanks,

Simon
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Old November 2nd, 2009, 01:54 PM   #2
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Simon...

That's something called "green spill", and there are keyers which have features designed to handle it.

However, note that there some types of green spill that are tough to handle. For example if someone is wearing white shoes or white pants, and they're standing on a green surface. The green that is bounced onto the wardrobe can actually turn part of the wardrobe green, and complicating the keying procedure.
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Old November 2nd, 2009, 02:30 PM   #3
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Hello,

Okay, so you confirmed what I thought the problem was.

Get rid of the green screen under their feet and keep it only in the background.

I will try it out.

Thanks alot,

Simon
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Old November 2nd, 2009, 02:48 PM   #4
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Any advice on green showing through fine or frizzy hair? I find that if I try to get rid of the green showing through I also tend to get rid of the hair.

Many thanks,
Alan
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Old November 2nd, 2009, 02:49 PM   #5
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Simon...

It is possible to shoot in a green screen environment, but just have to be aware of the capabilities and limitations of the software.

This is done a lot in filmmaking. For example in the scene where Leonardo DiCaprio and Danny Nucci run to the bow of the ship, they're working amidst all-green props. The deck, the railing, everything is green. These real-life surfaces are then replaced with digital models which place them on the deck of the Titanic at sea.

Here's some impressive examples of putting actors in an environment:

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Old November 2nd, 2009, 04:15 PM   #6
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Alan...

Regarding frizzy hair, there are a few considerations when shooting green screen.

-- Shoot in 1080p HD. Not interlaced. Square pixels. Get as much detail and image information at the very start. The Sony EX1 works well. I suspect if the image is recorded to 4:2:2 color, rather than 4:2:0, the results would be even better. But as it is, the EX1 does a remarkable job.

-- Make sure the lens is clean. Anything that softens the image will make it harder to key.

-- Don't overlight the green screen. A bright green screen will flare into the foreground and make it harder for the the software to create a good key.

-- Key the hair separately. What works on solid objects might not work as well on fine details like hair and smoke.

-- Using good keying software is as important as shooting a proper setup. I use Primatte. It's not cheap, but it can create a flawless composite.
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Old November 2nd, 2009, 06:34 PM   #7
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Hi Dean,

I will keep that in mind.

Thanks,

Simon
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Old November 3rd, 2009, 07:15 AM   #8
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Echoing what Dean siad, try reducing the light on the green screen. I've found that people tend to overlight, whcih cuase more light to be reflected onto the back of the talent.

Moving the talent farther from the screen has a similar effect as the reflected light falls off as you get farther away.

You might also want to add a magenta gel to the hairlight.
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Old November 3rd, 2009, 07:44 AM   #9
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Okay.

Good advice. I will try that out and see how the results come out.

Thanks,

Simon
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Old November 9th, 2009, 03:33 PM   #10
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Quote:
Originally Posted by Dean Sensui View Post
Simon...

It is possible to shoot in a green screen environment, but just have to be aware of the capabilities and limitations of the software.

This is done a lot in filmmaking. For example in the scene where Leonardo DiCaprio and Danny Nucci run to the bow of the ship, they're working amidst all-green props. The deck, the railing, everything is green. These real-life surfaces are then replaced with digital models which place them on the deck of the Titanic at sea.

Here's some impressive examples of putting actors in an environment:

Advertisement
The railing is green? Your kidding... usually stuff like that is real and the background is green, like the foliage in King Kong (Which had to be masked out frame by frame when the ceiling was seen behind it.)
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Old November 9th, 2009, 04:12 PM   #11
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Quote:
Originally Posted by Aric Mannion View Post
The railing is green? Your kidding... usually stuff like that is real and the background is green, like the foliage in King Kong (Which had to be masked out frame by frame when the ceiling was seen behind it.)
I was surprised seeing it. I think it was in a program called "Movie Magic". I can't find an example on the web. But there they were, running to the front of the ship surrounded by green props. An amazing bit of tracking had to be done to get the digital pieces to match-move the original shot.

It was done that way probably because the actors had to interact with the ship's structure.

Carl Sagan did the same in a PBS series, Cosmos, which placed him in a composited environment. The bluescreen stage had steps and platforms to match the scale model he was placed within. And two cameras -- one on the full-scale bluescreen set and the other in the scale modeled environment -- were synchronized. The compositing system would key out Sagan in real time, then place him within the scale model. It made it look as though he were in the library of Alexandria, for example.

Cosmos was back in 1980. Before digital motion tracking and After Effects.
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