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OT: Where to Post Green Screen Question?

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Norman Willis
OT: Where to Post Green Screen Question?
on Dec 7, 2014 at 6:57:44 am

OT: Hi all. I need some advice on a small chromakey studio setup. I have a bright spot in the center of the chroma screen on the back wall. I have four CFL's in key, and 2 CFL's in fill. I took the shades off of the lamps, but I still get a "bright spot" in the center of the screen. I am guessing the light is bouncing off the two side walls and ceiling, and is focusing in the center of the screen (like a parabolic collection point).



Are there any ideas how I can even the light out better? All I can think of is to put up commando cloth (duvetyn) on the walls and ceiling, to stop the light from rebounding. Am I making sense? (And are there better options?) Thank you.

Norman Willis
http://www.nazareneisrael.org


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Graham Bernard
Re: OT: Where to Post Green Screen Question?
on Dec 7, 2014 at 11:05:58 am

Hi Norman. What am I looking at? What are you ultimately trying to achieve? What happens when you test your CK-ing in VP? Do you need a large expanse of perfect CK or could you do with a less than perfect area outside of the target area and use a garbage matte?

I've got to ask, if you are so concerned, why have you those obvious folds in the cloth, delivering rolling shadows?

Cheers

Grazie

Video Content Creator and Potter
PC 7 64-bit 16gb * Intel® Core™i7-2600k Quad Core 3.40GHz * 2GB NVIDIA GEFORCE GTX 560 Ti
Cameras: Canon XF300 + PowerShot SX50HS Bridge


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John Rofrano
Re: OT: Where to Post Green Screen Question?
on Dec 7, 2014 at 12:01:54 pm

I use two soft boxes on my Chroma Key and I don't have any hot spots at all. Perhaps you are using too much light?

~jr

http://www.johnrofrano.com
http://www.vasst.com



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Bob Peterson
Re: OT: Where to Post Green Screen Question?
on Dec 7, 2014 at 2:17:01 pm
Last Edited By Bob Peterson on Dec 7, 2014 at 2:18:54 pm

One technique that's used in photography to obtain an even spread of the light is to use an L-shaped, white reflector on each side of the screen and a few feet in front of it. The reflector is the length of the screen with each side of the L a few feet wide. The lights are positioned facing the reflector rather than the screen itself so that all light on the screen is reflected. The caveat is that the technique was taught using a powerful flash pack, so the trick would be lights which are powerful enough.


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Graham Bernard
Re: OT: Where to Post Green Screen Question?
on Dec 7, 2014 at 3:38:52 pm

Diffusion is our friend. Reflectors or Soft Boxes, diffusion, nothing direct.

Grazie

Video Content Creator and Potter
PC 7 64-bit 16gb * Intel® Core™i7-2600k Quad Core 3.40GHz * 2GB NVIDIA GEFORCE GTX 560 Ti
Cameras: Canon XF300 + PowerShot SX50HS Bridge


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Norman Willis
Re: OT: Where to Post Green Screen Question?
on Dec 7, 2014 at 7:01:07 pm
Last Edited By Norman Willis on Dec 7, 2014 at 7:17:48 pm

Hi all. Good questions and suggestions. May I please make one combined answer here, and try to wrap everything in? The goal is a good clean key in a relatively small space, with minimal noise and spill, because we want to use a light-colored backdrop in post. So the noise has to go.

I tried CK before, with lights on both talent and backdrop, but I got a lot of green spill on the talent which I could not suppress (magenta, etc.). I am in a smaller space now (14 x 10), and my editor does not want a set(!), so after trying everything else I gave chroma another try, thinking maybe if I lit just the subject I would not get spill on the talent. I also pulled the shades from the key and fill, thinking that would give me more even lighting (but it sounds like that was wrong). Below is my existing studio-in-progress (with in-progress-mess).





My editor said he wanted a lighter, more neon backdrop (to get a better separation between talent and screen), so I found some cheap neon fabric (folded up on the table, in center) which I pinned up temporarily for the test shot above (which is why all the wrinkles). My editor likes the cloth, so I plan to get a rod pocket sewn in, so it will lay flat in production.

About the lights, due to past issues with green spill, I would prefer to start by trying to even out the lighting. And then if that does not work, then maybe I can try adding light to the screen? I am using CFL's, so heat is not a huge issue (except maybe in summer). However, if I use either reflectors or diffusers, won't that mess with the key and fill? And if not, which is better--reflectors, or diffusion?

I no longer have the stock reflectors, but if it will solve my problem I will get some.

Thank you all.

Norman Willis
http://www.nazareneisrael.org


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John Rofrano
Re: OT: Where to Post Green Screen Question?
on Dec 8, 2014 at 12:35:42 am

The CFL in that first shot is really creating a nasty hot spot. You need diffusion. Especially in a small area. I don't know how else say "Softbox" but that's what you need.

~jr

http://www.johnrofrano.com
http://www.vasst.com



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