Green Screen Homebrew - DIY retroreflector - white wall lit green
I've just been tasked with converting a 1000 m2 hanger into a sound stage in Crimea on the Black Sea.
This building itself has 12 meter high ceilings and a 5 ton rail crane in it.
I have a wall on one side of the hanger, I'd like to put a large green screen on it and do stuff like hang airplanes and cars from the crane.
Obviously, we could just paint everything green, but, if I could I'd like to be able to use the wall as a screen for projections as well.
in research, I've read a bit about the led technology, but them reflective bead embedded technology will probably not perform well with the distances and sizes I am dealing with, either a 12x6m or a 12x12 meter screen.
what I would like to know is if anyone has experience with some of the things we want to try and what would be best
a) a traditional green screen, a wall painted green (any specific color code to give to the paint shop?)
b) a white wall lit green. use a regular matte white paint and use green lighting to light it. projectors should give an even light
c) DIY retro reflector. Our idea is to use a glass sand and a reflective plastic film. For glass sand we were considering using windscreen safety glass and putting it in a ball mill to reduce the size of the particles to 1/10th a millimeter or so. This glass should crush into square particles. With this we are hoping to be able to use the screen as a projection surface and for a green screen.
I understand the technology behind the light from the led ring being reflected back at the lens at the same time it would seem that with another approach to lighting a much smaller light source could be used and still produce good results. I am also pretty sure that for telescopic shots the LEDs couldn't possibly perform as well as traditional solutions. With the building we've been given, we'd be able to work with the screen at distances up to 30-40 meters.
thanks a lot for reading my post and look forward to hearing from you. If anyone is looking for locations and inexpensive productions costs, please feel to talk to me about Crimea as a location. It's been pretty popular with the russian studios for decades, and we're seeing even American studios coming now (a new film "Soldiers of Fortune" with christian slater is being filmed here now.)
[David Stickney] "a) a traditional green screen, a wall painted green (any specific color code to give to the paint shop?) "
That's the best. Really. Don't mess with those things with the light rings around the lens -- they are useless for anything other than keying talent. Go look up the specs for Rosco chroma key paints.
A big green screen, properly lit, gives you the advantage of being able to light your subject separately -- you've got the room for that. The benefit: you can match the subject's lighting to those of the background plate.
[David Stickney] "I'd like to put a large green screen on it and do stuff like hang airplanes and cars from the crane. "
...which implies a camera that moves around the subject in THREE DIMENSIONS. You won't be able to do much movement at all unless the floor, walls, and perhaps even the ceiling are also green. For example: would you plan to shoot UP at a car hung from that crane? You could fake it by hanging the car upside-down, but then what is your background? The floor.
It also implies either motion control for the camera, or motion tracking in post.... and you'd better make darned sure you can do the appropriate motion tracking in post BEFORE you make the investment.
Another thing to consider: not everything is shot against green. Plants, for example. Kermit The Frog, for another. Post-production companies always leave themselves the option of shooting blue screen, too.
[David Stickney] "b) a white wall lit green. use a regular matte white paint and use green lighting to light it. projectors should give an even light "
Horrible idea. Don't do it. You seriously reduce your options for lighting the subject.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
The retroreflective cloth is so expensive because the round beads containing the corner reflecting elements are expensive to make and to align onto the substrate. You are not going to DIY this with crushed window glass. You "might" get a spotty response by using the Scotchbrite brand road marking paint system, but you'd need many gallons of it, and a way to apply it evenly. Worse, the illumnation to make the retroreflective system work needs to be right next to the lens. So for something bigger than a car, like a plane, you can't get enough big lights close to the lens to make the shot key right, and you'd be blinding/suntanning any talent in the shot at the same time.
I think in Hollywood, what they do for green screens of a scale this large is generally to make them self-lit from behind, using banks of lights shooting into a grid of green diffusion material, or colored lights on white diffusion. This does away with the bulk and interference of front-lighting the green and that gear getting in the way of the shot.
In your warehouse you'd build a scaffold-like grid, cover the front of it in a translucent plastic or cloth, and then hit it with banks of flos, HMI's or conventional lights from behind. The power and heat issues could be large, particularly with HMI.
Your LED comment sparked an idea: if you used the LED curtain or module displays used for big concerts, along *with* a layer of diffusion in front of that, you'd have a rear-lit green (or blue!) changeable screen that you could make adjustments to electronically, by the choice and modification of the image fed into the LEDs. And the curtain might be able to curve in a corner for a 2-wall setup. When you want to use the LED's to watch video with, for a rave party or something, you roll up the diffusion screen layer. You can simulate what I'm talking about on a small scale by holding some translucent wax paper or shower curtain plastic a few centimeters in front of a plasma TV screen, set the screen to show blue or green..
These kinds of huge rigs you're considering are uncommon for a reason: there is usually no justifiable business case for making this setup a standing permanent thing in one fixed location, so they are assembled temporarily for specific movie shoots as the time and budget and locations allow, then taken apart again. To tie up that kind of gear in a full-time permanent setup, in one somewhat remote location, that may only see an actual working shoot a few days out of a year, makes no financial sense. Doesn't mean it wouldn't be cool. Very cool. Just financially unsustainable. Sorry to be mister bring-down.
Thanks for the reply. I've never seen the material they use for the LED, I am assuming that it's a pretty standard retro reflector embedded in clothe, but from the sounds of it, that's not the case.
As for LEDs, a couple of years ago we wanted to make an USB driven LED dance floor, using multivoltage (multicolor) leds by the time we did the math on making the panels and buying the diodes and controllers, it worked out cheaper to simply use cheap lcd displays without housings.
Actually I've got some large displays and tried to get a key from them just for kicks, worked fine.
As for the justification of such a set up - I guess it's early in the game to say a lot, some of the factors:
This will be the only such sound stage in 600 KM
We're organizing a group for non commercial projects so a community resource is a motivating factor.
In the first week since getting approval on the takeover and conversion of the hanger, I've already gotten a deal to shoot a 30 episode series of a italian cooking show for an italian kitchen manufacturer and some good leads from Moscow based producers that come here to shoot anyway.
I'd love to have anyone who is planning to visit the area to come and visit, I am sure when you see the wide variety of locations withing 50 km of our studio you'll see why we think there is a justification for this stage.
kind regards, David
Thanks for your reply. You experience confirmed what I was expecting - namely a retro reflector or dual purpose surface would be an issue.
I probably will try to make some type of reflector screen and test it out, just to try it, who knows, maybe by playing around I stuble upon something interesting.
On another note, I've been reading the forum here for a couple of years and would like to say thanks for all the other stuff you answer as well. You're the kind of guy that makes the internet such a resource. I've read piles of your posts and they are alway solid. thanks for all the stuff you've contributed.
You should also read Mark's comments VERY CAREFULLY and take them to heart, especially about the business sense of undertaking such a project.
Mark's a businessman as well as a production guy. I just think things up, but Mark knows about paying the bills, too.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
That's news to my wife, Dave!
I'm not a businessman; I'm just a guy with opinions, fwiw.
You bet, I know a lot of people on this forum have tons more experience than me and really there is enough info in the forum already that most things have been discussed.
I'm not in Hollywood and my costs are a _lot_ lower than elsewhere.
While my location is fairly remote, it's been a long time favorite location due to all the various elements that can be found nearby.
I've been bring people onboard and I am pretty sure at the rate we're going we'll have a good bit of work to show for ourselves. In the future, I'd like to invite production companies to come to use our studios and I'm pretty sure I'll have a nice arrangement and very reasonable expenses. We'll pay for everything, even though we are pretty small now we have done the due dillegence and are ready :-)
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Maybe,.. I could easily fake California scenes here, except less smog, less illegal immigrants but with graphic Artists for $300 a month we can get that all fixed up in post.
India would be a bit harder to fake, maybe toss a bunch of brown food coloring on flour and thrown it in the water, we got cows...