goldnere,

I see no reason why it shoudn't work.

The key to greenscreen in my expereince it to light the greenscreen itself with an even and diffused light, and to keep the lighting for the subject well away from the screen with flagging.

I read somewhere recently that the best way to light smoke is with a three quarter backlight, aparently this reflects the maximum amount of light into the lense.

hope that helps a little

Paul

In what context are you shooting the smoke? Is there someone in the scene, or do you just need a plate for compositing?

In either case, ESPECIALLY the latter, I would forego the green screen and just shoot on black, then compositing with a luma key rather than a chroma key. It can be tricky to get the lighting to work and you may have to use some procedural mattes to get it to look right, but the advantage is that you can give smoke the transparency it has in real life, without creating weird boiling edges or color spill.

I am of the opinion that a luma key will yield better results in most situations anyway (again, no color spill, better gradiations from transparent to opaque, and in DV, the luma channel is less compressed than the chroma channel).

-----------------
Andrew Gingerich
Exploding Goldfish Films
Check out my vodcast on iTunes: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=96931870

I agree about Luma keying, especially with DV, and ESPECIALLY if you're trying to key smoke. It's much easier to key the smoke in front of black than green. In fact I would go so far as to say I'd rather use animated particles to effect smoke than do a greenscreen key for it on DV, especially if it's a minor element in your scene.

thankyou very much for all the help. In regard to agingeri's question the smoke is not all that would be filmed. The shot would basically be a person blowing out smoke from a profile angle, their is equal empahsis on the smoke and face in this situation. I am using school equipment and have access to a green screen but none of the other alternate methods mentioned. Thankyou very much for the help everyone. Take care : )
-Ed

If you're talking about using a hardware-based video switcher to pull a chroma key, don't even think about smoke. For all the advantages of hardware-based keying, they simply CAN'T do transparency. I don't have much experience with keying hardware, but I think most come with a luma key option, which would be preferable but still not ideal. If you can get ahold of Adobe After Effects, that would be the way to go, especially for advanced luma mattes. Even Final Cut can be a decent keyer, and if you really want to use a green screen, dvGarage's DV Matte looks promising (though I haven't tried it): http://www.dvgarage.com/pgroup/pgroup.php?pgroup=comp

Most important thing to remember: LIGHTING. Make sure the background is evenly lit! I don't suppose you have access to a vectorscope (that's the best way to judge such things), but you may be able to set 'zebra striping' on your camera to indicate areas of similar exposure. Try not to trust your eye. I have in the past, and it always leads to problems.

Another good trick is to get your talent out away from the background as far as possible so you can throw it out of focus (this tends to cover up blemishes and make for an easier key).

-----------------
Andrew Gingerich
Exploding Goldfish Films
Check out my vodcast on iTunes: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=96931870