Lighting a Green screen

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DVX100Shooter

Veteran
I was watching the Making of Video on BET the other day and they had the artist and several dancers all in front of a large green screen. I was amazed at how there was no shadows! How many lights are needed to achieve that? I did notice a very large softbox light hitting the green screen itself. I have no idea what they used or placement of the other lights for the talent.
 
Re: Lighting a Green screen

To achieve a good speration you will want to have the green screen 2x brighter than your talent. A good back light (placed high and to the side) will also help to sepearte the talent from the green screen. To prevent shadows, usually you will have to move the talent far enough away from the screen and the Green screen should be lit with different light sources than the talent. And of course don't let your talent wear anything remotely green.

Was the BET video being shot in an exterior situation or in a studio?
 
Re: Lighting a Green screen

I just recently shot a standup on greenscreen with two 500s on the screen Lit space about 8X8- the talent 8 feet from the screen with two 250s and white bounce. That's four lights and it worked well.
 
Re: Lighting a Green screen

Craig
having the green 2X as bright as the talent will not work well. White faces should be at about 60 to 70 IRE and the green should not be above 80 ire and prefferably around 60. 2X brighter would place the green at 140 IRE!
 
Re: Lighting a Green screen

The thing is, you want to light the green where the chroma level will be the highest. If you're really trying to nail the exposure down, first do a test pointing at the actual green screen you'll be using stepping through the exposures. Then look at the footage with a vector scope and see what exposure gives you the most chroma (it'll be a moderate exposure, not "bright" nor dark). I suppose if you have something nifty like DVrack you could do this live on the spot.

Anyways... that's how you want the screen exposed... period. Then how you light the foreground is up to you (whether is generally "brighter" or "darker" than the screen really kinda depends on what you're shooing).

If I wanted to wing the whole thing I would say let the camera get an auto-exposure off the screen, then light a black face so that it hits about a stop beneath that.... which is what I've heard as a rule of thumb for dark complexions. (.5 to 1.5 stops beneath medium gray depending on the complexion)
 
Re: Lighting a Green screen

The key to not getting shadows is having the talent/subject far enough away from the screen that shadows don't fall into the screen, plus the height of the lights makes a difference as well. The same rule applies in photography.
 
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