Shooting Fire - Green Screen

[Mitch Martinez]

Hi All,

I have a shoot coming up where I'm supposed to be shooting fire for compositing and the question was posed whether to do it green screen... or black screen and just switch the black information to the alpha channel.

My gut tells me black screen is the way to go for the flames to ensure that the varied colors don't get lost in the keying process.

To make things more interesting, the flaming object is actually going to come in contact with the black (or green) surface)... It's supposed to be dropped onto it and the surface swapped out in post. We'll be taking lots of controlled environment and safety measure to make sure we don't like my hometown on fire.

Thoughts? Suggestions? Experiences?

 

[Stefan Christou]

No experience but a luma key sounds like the right option. I'm not sure how a transluscent element would react to green screening wihtout just looking green.

 

[Mark Allen]

I've actually never seen fire shot over green screen. When you shoot it over black though a luma key is not enough, you need to get the base volume of the fire in there especially in the core and for that you need to do some roto - even if it is rough because otherwise it always lacks the center body and seems basically dissolved. I would imagine if shot on greenscreen it would have the same problem, but I honestly don't know.

 

[Mitch Martinez]

we shot it today against black. I'll let you know the results when we get it into post.

fire is quirky - especially when you shot outside and have a variable direction breeze.

cheers!

 

[RikiButland]

I have always shot flames against black, always worked out fine using a luminance and difference key, a little fiddly but not too bad

 

[Joe G.]

I also used black with fine results.

Not sure what you're planning with burning your background though?

 

[Nick Burridge]

Been a while since I comped fire but used to do it with stock shot on black, then comping in 'Add' mode (in 32bpc - 8 and 16 give wildly different results). Season with a small compound blur on the background (based on the luminance of the fire clip) to taste.