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Old April 23rd, 2006, 07:17 PM   #1
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Doing green screen in the sun

So, I am going to try and do some green screen work in the sun.

My goal is to try and do some "rear-projection" car driving dialogue scenes like they do in old movies. I'm not trying to fool the audience as much as create an aesthetically pleasing suspension of disbelief.

However, my past experience trying to greenscreen with a A1U (Sony HDV) was unsuccessful. I had lots of jaggies, i.e., I wasn't able to cut a clean matte in Adobe After Effects at all.

Also, someone told me that maybe the color depth of an A1U might be a problem--that I'd be better off with a Z1U? But in my experience, the A1U has just got categorically better color than a 3-chip prosumer miniDV cameras like an XL1 or DVX.

Can anyone give me any advice?

Will the sun light the green screen well enough?

Should I build some kind of frame or will hanging it from a garage be suitable enough?

Do I have to worry about the angle of the sun?

Should I iron the green screen before use? It has been folded up for a few months.
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Old April 24th, 2006, 06:33 AM   #2
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i thought about doing it outdoors as well. of course one issue is the squinting of your subjects if the sunlight is strong

If i where to try it i would do it around 10am or so when the sun isnt too high up yet or possibly on a lightly overcast day or in the afternoon at around 3pm

overcast would give you a diffused light but you may want some more pop on the subjects.

as far as the chroma keying is concerned have a look at Serious Magic Ultra. It seems to be doing well with compressed footage.
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Old April 24th, 2006, 09:39 AM   #3
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It's like shooting anything else - it's really important to get your green screen properly exposed - too hot or too dark and it won't work. Make sure your colour balance is correct.

Keying is going to be problematic from any single chip camera as the colours are captured as a composite as opposed to component nature of 3 chip sensors. However the more advanced CMOS sensors (AU1) should be capable of capturing enough colour info.

You should be able to get acceptable results from a decent keying package - depending on the version of AE you are using I never liked it for chroma keying. Usually your NLE will include something pretty good without buying anything extra.
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Old April 24th, 2006, 08:07 PM   #4
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Thanks.

I heard similar things about on the subject of this 1-chip CMOS. It's possible that I would be able to borrow a Z1U. I'm curious to know how much of a difference the Z1U's added color depth would make in terms of cutting a clean matte.

Is there any other general advice anyone might add?

What about simulating the reflections of passing trees and buildings? Stuff like that..
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Old April 25th, 2006, 06:31 AM   #5
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I actually did the exact thing that you are trying to do and actually got very good results. Here are some suggestions I would make though.

Build a frame for the green screen and make it large enough so you can move it closer or farther away from the car to get the right lighting on it without producing artifacts. I had mine about 8 feet away from the car but that could vary based on how bright the sun and what angle the sun is etc. I built my frame with some 1/4 inch plywood and some 2X4's and was able to just pick it up and move it.

Make sure the green screen material can not be blown around by the wind and is perfectly flat so you don't get any color variation. If you have wrinkles in your screen material I would probably try and flatten them out.

Depending on the angles you are shooting you will probably need to throw some light on the actors in the car to get proper exposure...especially if it is a bright day. I just put some CTB gels on some lights and lit the actors that way.

The sun lit the green screen very evenly and made for easy keying...the scene really looked great when everything was put together.

Hope this helps a little.
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Old April 26th, 2006, 10:05 AM   #6
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it helps A LOT. Thanks very much.

I'll try and follow this method: http://homepage.mac.com/geerlingguy/...eenscreen.html
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Old April 26th, 2006, 02:15 PM   #7
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That's a pretty cool way to make a backdrop holder that would be lightweight. I will have to bookmark that for future reference.

We get some breezy days up here so that is why I used 1/4 plywood for the outside shoot otherwise the screen would have been blown around a lot.

Good Luck!!
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