GREEN SCREEN ADVICE REQUESTED

Hi.

I'm Bill from Arizona, shooting with a Canon 6D.
Project is feature length film.
My plan is for indoor set using 20X20 portable, hanging screen.

Would like some input as to the following:

1. Which fabric/material is BEST for KEYING? I've heard foam-backed gets best result.
2. Where to purchase screen considering quality and price?
3. Given material recommendation, which Green Screen lighting gives sufficiently professional results?
4. Given lighting advice, should matte-box always be used during filming?
5. Finally.., as to the dimensions of the green screen: Is there a site I can visit which indicates how much can be filmed in various sizes of green screens, ie. 20X20 allows for 5 people sitting at 5' diameter, round-shaped table?

I appreciate any and all advice.
Thanks.

Welcome to IndieTalk!

burrus1206 said:

1. Which fabric/material is BEST for KEYING? I've heard foam-backed gets best result.

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As fabrics go, foam-backed seems to be the best option, I've had good results with it. It definitely minimizes issues with wrinkles, etc in the fabric. You'll want to store it rolled though, not folded, as once it develops wrinkles from folding they can be hard to get rid of.

2. Where to purchase screen considering quality and price?

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These guys have quality fabric, not sure how they compare pricewise to other companies though - they charge about $650 for a 20x20:

http://www.eefx.com/

3. Given material recommendation, which Green Screen lighting gives sufficiently professional results?

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Best results generally come from Kino-Flos - the diffuse nature of the light and size of the source makes it easier to get the lighting even on the background. A cheaper alternative would be Cool Lights' kino knock-offs:

http://www.coollights.biz/

20x20 will take quite a few lights to do evenly across the whole thing, you'll probably need at least three fixtures up each side and at least as many across the top as well. Even with the cheaper fixtures you're looking at a $2-3k in lighting. Renting lights will be significantly cheaper. Depending on how long your shoot is, it may be less expensive (and certainly easier) to rent a soundstage which is already set up for greenscreen.

4. Given lighting advice, should matte-box always be used during filming?

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Depends on your lighting setup for the foreground. The background lights should generally have barn doors/flags to keep the light from spilling on to the foreground, so the light source shouldn't be visible to the lens. If your foreground light sources are exposed to the lens at all then you'll either need to flag them or use a matte box.

5. Finally.., as to the dimensions of the green screen: Is there a site I can visit which indicates how much can be filmed in various sizes of green screens, ie. 20X20 allows for 5 people sitting at 5' diameter, round-shaped table?

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Too many variables to calculate this effectively. How far are your subjects from the background? How far is the camera from the subjects? How wide a lens are you shooting with? You really need to set up a similar scene and then calculate from there how big a background you need. Backing the camera off and using a longer lens will minimize the size you need to cover the background. At the size you're talking about I suspect finding a soundstage to rent may be the better option, fabric is generally best for small set ups with one or two people at most.

The other thing to consider if you're putting that many people in front of a greenscreen, or even just one person really.. is if the camera is going to move, at all, you need tracking marks on that screen too so you can do a camera solve in post and move the background accordingly.

Best way to figure out how much you can do would be to previz in a 3D application.
You can do a dumbed down version of this by calculating your camera angles and drawing a scaled top-down image.

You'll want to keep some margins though, if theres only small parts people getting off your greenscreen, the rotoscoping gets tedious really quickly (especially on long shots, which seems to be what everybody wants these days -,-)

Don't forget to test before really starting shooting your feature.
Maybe the codec isn't adequate enough...