Silhouette effect with moving camera

aldo12xu wrote on 8/25/2006, 11:43 AM
I realize I might be asking a lot. I read about how "difference key" can help create an iPod type silhouette effect. I will be filming a band performing live in front of a green screen, with the camera zooming in and out and changing positions. It seems that using difference key only apllies to a stationary camera.

Is there any way I can have the band members silhouetted if the camera is moving? Basically if I could tell Vegas, "anything that does not have a green colour, assign it a black colour". that would do the job.

Thanks in advance,
Aldo.

Comments

epirb wrote on 8/25/2006, 12:06 PM
One simple way i just shot against a green screen is to simply light your green screen brightly, and dont use any lighting in the foreground(ie bandmembers) and set the exposure for the background. your band will appear black silhouettes and the screen is perfect for keying . makes for good masking too...
richard-courtney wrote on 8/25/2006, 3:53 PM
You can use Mask Generator and select Green.
If needed you can child this and invert.
The other way is Chromakey and Show Mask.
We did this for a tennis opening and was very well received.
Either way you can get a solid moving character with your desired background.
farss wrote on 8/25/2006, 7:07 PM
Well for this you don't even need a green screen.
Just a white backdrop would do, light the backdrop only.
Or do the reverse, black backdrop and light only the band.

Trick is to have the band and all their bits and pieces having the opposite and that might be difficult, even using chroma keys you need to be careful that there's no color the same as the background in what you want from the foreground.

However as you're not seeking a photorealistic key you can fix things pretty easily in post even if there's the odd bit that's not keyed properly.

To get back to the original question, yes, one could use a difference key with a moving camera. HOWEVER you need a background plate that's exactly the same. That means some expensive kit that can repro exactly the camera movements, lens focal length etc.

Bob.
Spot|DSE wrote on 8/25/2006, 7:37 PM
Jim H's "Ethics" video does this exceptionally well, and he has a fairly long post about it if you search around.