June 21, 2018 at 11:59AM

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Greenscreen vs. Bluescreen for keying

Hello NFS. Does anyone have a strong opinion one way or the other as far as using a greenscreen vs a blue screen for keying in post? Building out a production space for a shoot in July, thanks!

8 Comments

Green is better in my opinion. It's a less likely color for people to wear.

June 21, 2018 at 1:24PM, Edited June 21, 1:24PM

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Thanks, I was thinking the same thing originally. I've read that green has a more chance of spillover onto the subject... but it does seems that blue is rarely used versus green screen.

Mike Halak

June 22, 2018 at 10:22AM

So the primary colors of light are blue, green and red. Our skin contains mostly blue and red tones. This is why green screen is the most common. It gives you the cleanest key with most skin tones. That being said, most cameras these days, if they have noise in the shadows, it typically tints blue. So this is also a benefit if you are using a strong dramatic lighting on the subject as the shadows are less likely to have green noise than blue. The last reason I would suggest green is because the bayer filter that cameras use to interpret color has more green photosites than any other color.

If your subject is going to have to wear green (like you're shooting a leprechaun or something) than definitely go blue, but if you can control what your subject is wearing, I always go for green.

That being said, helpful tip that I wish I read before the huge green screen project I just finished for the local chamber of commerce, if you use After Effects for keying, expose the green screen roughly 1 stop less than your subject. Keylight (the recommended keyer in AE) handles it better when it is slightly under exposed.

Anyway... Good luck!

June 22, 2018 at 3:01AM

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Matthias Claflin
Videographer
542

Thanks for the info, this is comprehensive! My subject will be wearing a white labcoat (LOL no Leprechauns), I'm keen to avoid spillover.

Would you elaborate on exposing the green 1 stop lower than the subject - do you mean building a composite of keyed layers in AE? I'm a bit fuzzy on how to structure multiple exposures. Thanks for taking the time, it's appreciated!

June 22, 2018 at 10:19AM

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Mike Halak
Art Director +
80

When you light the green screen, just dim it a bit more than the key and fill on the talent. I'll share a screen shot below to explain what I mean. The way I checked this for myself, was to have the subject stand out of frame and set the waveform to about 35-40% and then have the subject stand in and add light to get them between 60-70%. Just make sure your light doesn't spill too much onto the screen.

To avoid spill, move your subject as far from the green screen as possible. If you are in too tight a space, set the lights up to hit the green screen from a near 90 degree angle. I've had some luck with that.

So the first photo is of myself and my business partner when the green screen was set up. We used four fixtures with softboxes. Each fixture contained five 35w CFL bulbs (similar to a spiderlite). On the green screen we had one softbox on either side set to only have 3 of the 5 CFL bulbs on. The keylight on the talent was set to have all 5 bulbs on. The hair light behind the talent was at 4 bulbs. In hind sight, I would have turned down the hair light. I don't like the hard white edge it created personally. That being said the talent stood about 6 feet from the screen and I shot on an 85mm lens with my camera about 20 feet from the screen. The whole thing was shot on my C100 mki with a cheap tablet based telepromter.

The other photos are what the camera saw. We shot in log, (I wouldn't actually do that again, but I was afraid I'd miss exposure) so I added a log to Rec709 lut to the images.

https://flic.kr/p/JMJH64
https://flic.kr/p/25FGHKy
https://flic.kr/p/JMKByR
https://flic.kr/p/25FGJ7f

June 22, 2018 at 11:58AM, Edited June 22, 12:00PM

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Matthias Claflin
Videographer
542

Hey Matthias, thanks for providing such detailed responses, this info is great and the setup images + bulb configs are helpful. I've shot a green screen on a small scale, but it's my first rodeo for a larger scale/live action setup. Thanks again!

June 23, 2018 at 12:54PM

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Mike Halak
Art Director +
80

There are times I wish I had gone blue rather than green because of spill. Blue spill especially from a (fake) window is a LOT prettier than green spill. Yeah it shouldn't have been there but....

June 27, 2018 at 11:50AM

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green is better when you shoot with dslr and cameras that shoot in 4:2:0 where 4 is luminance (green), blue had half of infos and most of compression work on color channels.
Blue is better when you need to spill around some subject, today is simple to own or rental a good recorder or camera that shoot raw, 4:4:4 or 4:2:2 in a good quality recording.

July 3, 2018 at 5:37PM

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Carlo Macchiavello
Director
799

Please correct me if I'm wrong, but isn't green used as the green channel has a higher resolution compared to blue and red because of the way photo sites are aligned on the Bayer-filter?

July 4, 2018 at 4:49PM

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