I have an idea that might be able to eliminate a lot of the cost and a lot of work involved with chroma-key screening. I have access to a couple of expensive projectors and a few not-so-expensive portable projectors. I also have access to some solid white backgrounds. Here is my idea:

I set up one of the projectors (or maybe more than one) so that a beam of solid colored light fills the white background but doesnt hit the talent. I take whatever shot I need. In post-production I carry on the normal chroma-key substitution process. ...Would this idea work?

If this method works, it would save all the time that it takes to light a normal chroma key screen. It also saves money.

try it?

i bet it does! i know you can key a blue sky out and this is very similar (also luminous) - tell us if it works! sounds awesome.

I think Im going to run a test shot sometime this week. Ill let you guys know how it turns out.

The only thing I can imagine going wrong is the projection screen interfering with your picture like shooting a TV screen does. I imagine it equating to the green background flickering and possibly confusing the chroma-key software. At the very least it should be an interesting effect. Although, in all honesty, why not just film the background and project, all old-school? I actually prefer that to chroma-keying (at least if it's involving driving a car.) The flickering will more than likely cause it look like your footage was projected anyway, so let us now how it turns out. Maybe we'll find out why no one's done it before or since.

-Elliott

Yeah... I don't don't think that would work. Like my third or fourth favorite Transformer said about the flickering, I agree. But then again maybe natural evolution of technology has eliminated the flickering that was proficiant back even 5 years ago.

Now, like you said, I'd probably hit that wall with atleast two projectors, to get a nice solid colour, or... increase the size of the "blue screen".

It might work, but don't you think Hollywood people would be using green projectors instead of spending all that money on blue/green screen walls/setups/lights?

it doesn't flicker. i've used that technique to project video behind an actor. doesn't look like chroma keying if you do it that way though, looks like a guy standing in front of a skewed washed out blurry image

I personally dont think it will flicker. If it does flicker, the XL1s have a function to stop the flicker. (so you can record the TV and computer screens). Im going to try to test this out tomorrow.

If we're talking LCD projectors, there should be no flicker, as the images are progessive. For a CRT projector, you probably can set the refresh rate to 60 Hz to sync with your camera, assuming you're shooting 60i.

I don't see however how this is going to "eliminate a lot of the cost and a lot of work involved with chroma-key screening." If anything it sounds like more work and more expensive, but if you have access to the stuff, then by all means proceed and report back.

I have free access to 1 LCD projectors and two CRT projectors. It eliminates the money to buy large green screens, and it eliminates the time and effort to light it properly.

Well not really. Projectors don't project an even amount of light all through the image they project, and the lens on the projector isn't necessarily the highest quality, so it might lose a lot of light near the edges.

so then you end up with the same problems that shadows present (you end up with different greens) or you have to light the wall in such a way that you cover everything in an even green color from teh different projectors and from the overlap that may happen.

So you have to shape the light of the projector just like you would a spot light or a flourescent light, and then worry that all the projectors are projecting an even green color, whereas lighting, you just worry that they're all the same kind of light: tungsten, daylight, or whatever color temperature you need.

Why does everyone use so much green screen anyway?