Greenscreen spill - general question

Posted by stefangs 
Greenscreen spill - general question
August 11, 2015 10:09AM
Hi all,

I've experimented today with a greenscreen setup outdoors in bright sunlight. The spill was quite heavy, so I increased the distance between the subject and the screen to about 4 m. This was only a test though, because my folding GS was now just about large enough to cover head and shoulders.

To my surprise the spill was just as large as before. Is it because the bright sun bounces back so hard that you'd have to move the subject half a mile in front of the GS or is there some other reason I don't understand?


macpro 2x3 ghz dual core intel, 10.6.8, FCS 2
Re: Greenscreen spill - general question
August 12, 2015 07:28PM
if you change your setup so that the sun is behind your subject,
you will get a strong, non-green, rim light.
Re: Greenscreen spill - general question
August 14, 2015 12:14PM
[post removed as non-germane]
Re: Greenscreen spill - general question
August 16, 2015 02:13AM
Dear stefangs,

It is true that you have to be half a mile away from the screen to avoid spill. Two miles is the ideal distance.

However, I agree with Nick about backlighting your subject. But then you may lose the power of the sun shining directly on your screen, right? But that's better because the screen will reflect less light on your actors.

Here's what I do: I backlight the subject using a light magenta gel. The magenta then "cancels out" the green spill. But if you are out of doors you will need at least a 2k backlight - and then some. But it does actually work ... fire up the most powerful lamp you own and SPOT it on your subjects as a backlight.

On the other hand, if you are lazy like me, you just shoot the thing and mess around with the green spill problem in post. Frankly, it's a miracle if you can get the actual green screen to stop waving around in the breeze when shooting an exterior ... I've been there recently with a 30 ft wide greenscreen waving around like a reject from a round-the-world yachting race.

The main point is that, if you are EXT DAY GREENSCREEN, and your actor is not perfectly placed to avoid green spill, you will inevitably get green spill.

Think of this problem as an existential challenge.

Your reward will be in heaven.

Hugs, Harry.

PS. I hope that Nick agrees with me because ... he frightens me a bit.
Re: Greenscreen spill - general question
August 18, 2015 04:08PM

thank you all for enlightening me on all ends of this problem. If anything, it's comforting to hear that it's normal to have to deal with spill and not my particular noob problem.

I'll try backlighting next time, although probably more so indoors, because I don't have lights that can give the sun a run for its money.


macpro 2x3 ghz dual core intel, 10.6.8, FCS 2
Re: Greenscreen spill - general question
September 15, 2015 03:04PM
In my experience the brightness of the green screen is not as important to the key as the saturation. Lots of DPs pour vast quants of light on a backdrop to get it to be bright and even. This leads to lots of green spill.

To help your outdoor problem, you might try flagging the sun light on the screen down a stop or two.
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