High Contrast lighting against a Green Screen

John Carreon · January 17, 2008

Hey Everyone,

I'm going to be doing some green screen work soon and they want the subjects to be lit pretty contrasty...noirish...

My question for you guys is how bright do I have to get the Green screen to be able to get a decent key off of it while still being able to use contrast on the subject.

These will be full body shots so I have to be able to get a key off the floor also...

Hopefully this makes sense.

Shooting on the HVX200

Thanks,

John

Chris Keth · January 17, 2008

The general ballpark is to get the screen around 50IRE and as even as possible. That shouldn't be a problem at all with the background, as always separation between subject and screen is your friend. The floor may be tricky but this may be where costuming comes in handy. If the talent is clothed a bit dark then the illusion of dark will remain, while still lighting the floor for a good key. I haven't done a ton of full body greenscreen so there is probably a better solution (which, no doubt, someone here will offer), but this could certainly be helpful.

Edited January 17, 2008 by Chris Keth

Michael Nash · January 17, 2008

If you can't avoid hard shadows falling on your greenscreen, the basic technique is to pull two different mattes in post -- one for the "lit" level, and one for the "shadow" level. It's more work in post, but sometimes it has to be done. Sometimes you can fill in a shadow with soft light to bring the luminance back up a little, without contaminating the lighting on your subject too much.

The easier approach would be to just have the feet go dark, and have the hard lighting side-y enough that the shadow doesn't fall on the greenscreen floor anywhere near the subject. Remember that you only need a clean green screen around the subject; Shadows and flags that don't touch the subject in frame can be garbage-matted out.

Jess Haas · January 17, 2008

I have noticed that the dark sides of peoples faces have the annoying habit of picking up green spill off of the floor. Make sure you have something to lay on areas of the floor that the actor doesn't cross in order to minimize this.

If your floor is the brighter "digital green" you will find that you need surprisingly little light to light it. I highly suggest doing some tests and involving whoever will be doing post to see what you can get away with.

~Jess

Jess Haas · January 17, 2008

Another quick thought. If you light the floor mainly from high, back and the same side as your key it should stay out of the dark side of your actors faces while only creating a shadow in front of them which shouldn't be very problematic.

~Jess

Scott Fritzshall · January 17, 2008

The general rule for lighting a greenscreen (depending on who you talk to I guess, but I've found that this tends to work very well) is that you want it 1/2 stop under key. However, you should modify this based on how bright the final background will be. If it's going to be very dark, then drop your lighting down, if it's very bright, then make it brighter. This way the spill light you're getting will be somewhat in line with what would actually be coming from behind. More important than exactly how bright it is, however, is that it's lit as evenly as possible, and that you get as much distance between the subject and the screen as possible.