Sorry to have to say this, but at first blush, you'll be lucky to do 2 people at a desk with a studio that size. 20x13 is not very big at all for any kind of ambitious green screen work. It would be great for static product shots, but not for mounting a bigger video production.
With as small a space as you have, I'd concentrate on the green background for the desk, paint the ceiling white for bounce light, paint the other walls black, and hang backdrops for variation when you bring other things in. You'll have to get creative with backdrops, because the space doesn't allow you to get creative with green screen. I'd think about mounting some hefty pipes along the studio perimeter very close to the ceiling (aka "battens") to hang backdrops.
Once up & running, you will be absolutely stunned by the speed at which you run out of space.
To go all the way you should paint 2 walls and the floor green, everything outside the green walls black and install a cyc in the corners of the wall to give yourself curved transitions. I would hang some pipes or a lighting grid in the ceiling and install a bunch of 20 A outlets in the ceiling and along the other walls.
I've had the very best luck with Rosco Chroma Key paint. Here's a link to their how to: painting a green screen : Rosco Spectrum. Be sure and look at the section on choosing the color. If you have a fair haired main talent that is going to be on set most of the time Blue may be better.
This is a great source for a Cyc Wall: Affordable Cyc Wall Systems | A cyc wall insert that is affordable and quick to build.
Even if you are working on a tight budget I find that a professional studio paint will be cheaper in the long run than running down to Home Depot and having them mix up a gallon.
Thanks for the recommendations.
The cyc system sounds neat but too expensive for me at this point - spoke to them and would be several thousand dollars for the back wall and corners; over $1000 just for the back wall.
In terms of Rosco paint - they do have a store in my town that sells Rosco's products, including the ChromaKey paint for about $86 / gallon.
EDIT Actually found Rosco Chromakey at B&H for $75 / gallon with free expedited shipping - still kind of pricey but I'll do a little more reading then probably take the plunge.
Do you know if this is different than / superior to Tube Tape's Chroma Key paint? The latter is a fair bit cheaper, though I would have to pay shipping, but if I got more than one gallon might be worth it.
Any thoughts about the muslin green screen backdrops as opposed to painting?
I won't be taking this on the road - so mobility is not an issue.
I like the foam backed commercial chroma key fabric. This is the top of the line: EEFX Overhead / Butterfly fabric. Chroma Key Foam Backed. It's a little cheaper without the grommets and you really should invest in a butterfly frame for all 4 sides and a bag to keep it clean.
This is similar material from Digital Juice and it's pretty good but not quite as durable: Digital Juice ChromaPop Studio (12 x 18') CHROMA.POP.12X18.WC | B&H Photo Video
89% or more of my keying projects are shot with foam backed fabric setups. I seldom put the fabric on the floor and let folks walk on it unless I absolutely have to key the shadows. The lower half of a body is so easy to mask with RotoBrush if I need to knock out the feet. If I must have a lot of walking on the fabric we use sticky covers for shoes or use much cheaper plain muslin that is close to the same color and charge for it as an expendable. BTW, if you buy the right clots the Rosco paint will match the color close enough that you can paint a floor if needed.
Hey Rick -
I ordered two gallons of the Rosco Chromakey paint you linked to, which should give me plenty to cover the end of the room and floor in that area.
Do you have any recommendations in terms of an undercoat for the sheetrock?
I thought they were going to put on a white primer, but when I went to check they'd actually put on something beige - no idea why; wasn't a color we were using elsewhere in the house either. At any rate, would it make sense to put on a coat of inexpensive green paint for an undercoat just to minimize any reddish or yellowish color coming through? Can obviously do more than one coat of the Chromakey paint but that's still $75 / gallon even with the relatively good deal I found at B&H.
Also, if I go with black everywhere else, anything special I need to know about that - or just any standard flat, non-glossy black paint?
And would you give any consideration to the idea of painting my relatively low, 9' ceiling white so I could bounce light off it - or will that create enough problem with green spill that it wouldn't be worth it?
In terms of lighting, I went with a ceiling suspended on resilient clips, with 2 layers of 5/8" sheetrock decoupled with GreenGlue from the Sound Company - so my ceiling is into these clips instead of the joists. I did put some plywood in the top layer to it could support some relatively low weight lights or help hold the weight of a pole/light rig going across the room. I'll probably start with some floor lights, but the room is only 13 feet wide, so would be nice to get things off the ground if possible - would consider anchoring lights to studs along side walls (via movable arms) or in ceiling as long as not very heavy. Open to suggestions here as well.
The Rosco paint will cover anything in one coat, that' why it is expensive.
There are some very simple rules for lighting sets like the one you describe. Key the short side of the face, 45º angles, fill ratios. If you are new at lighting I'd look at some examples. They are all over the web. Here's something that you probably didn't think of. You don't need a lighting instrument to have a light source. You can use a reflector. With low ceilings I often stick reflectors on the ceiling and bounce lights off them. You can simulate any type of light by bouncing if you have the right kind of reflector. Smooth and shiny will act like a focused fresnel and matte (like a white show card) will simulate a soft box if you point a wide beam at it. In very cramped spaces, to get a pleasing overhead light with the right kind of fill I have often pointed a narrow beam light at a shiny reflector taped to the ceiling instead of trying to rig a light in the ceiling.
If you have room I'd probably light the set with soft boxes or diffused light first and then add just enough fill go fix dark spots in the green screen. Lighting the foreground first, especially in a small studio, will give you just about the right exposure on the back wall because of the inverse square law. There is a real strong temptation to put way too much light on the green screen. For best results the GS must have a lower luminance value than a caucasian face.
Also, remember that only the green screen behind your moving actors needs to be nicely lit. You can garbage matte everything else out and save yourself a ton of work in the studio. I just shot a pilot. There was no green screen involved but it was all on location in small rooms. For the most part I lit most scenes with 2 lights and 4 or 5 reflectors and 4 or 5 flags. If you know what you are doing it's very easy to light small spaces with a few instruments, flags and reflectors. For the setup you described maybe 2 lights on stands in front of the desk and 2 lights high in the back as backlights, a couple of big reflectors on each side of the set to smooth out the green screen and a few flags to control spill and I'd be done.
I'm going to add that green screen is not magic. Properly lighting and exposing a green screen shoot is complicated but not difficult. Chromakey filters are not one-click no-brainers. Just keep opening the twirlies to see the dozens of options that can often require careful tweaking. A waveform monitor and a light meter are great tools to learn how to use. Barndoors on your lights. Rigging flags. Backlight gels are also helpful.
best of luck.