character in front of green screen?

J. Scott Portingale · October 25, 2007

I am lighting a puppet style character in front of a green screen. I heard from somebody that I needed a special gel to back-light the character to avoid the fake green screen look. Is this true? If so what is the gel called? Should the strength of the back-light be a stop higher or lower then the key light/s?

Michael Nash · October 25, 2007

If your subject has fine, wispy white or blonde hair/fur/whatever, a magenta (minusgreen gel) backlight can help separate that detail from the background a little bit. But otherwise, you don't necessarily need a colored backlight (or any backlight, for that matter) to pull a clean matte. All you need for a clean matte is a sharp edge of something that's not green against a saturated, solid green background. Wispy hair or fur can sometimes be too fine a detail for some keyers, so making it stand out with backlighting can sometimes help.

Regarding how bright to make the backlight: light it the way you want it to look in the final comp, 'cuz that's how it's gonna look in the final comp. If you don't want a backlight on your subject in the final composited image, don't use one when shooting the foreground plate (greenscreen shot). Over-lighting your subject for the purpose of pulling a clean matte is going to make your comp have more of that "fake green screen look" than if you hadn't done anything in the first place!

Edit: when using minusgreen gel start with the lightest grades and increase density until reaching the desired effect. If the magenta color is visible on your subject when shooting, it will look that way in your comp as well.

J. Scott Portingale · October 25, 2007

thanks for the tips. I'll give it a try

Jonathan Bowerbank · October 25, 2007

I've used the minusgreen backlight before, and when shooting standard definition DV it helped quite a bit in post to get a sharper separation between the actor and the green background. I've also used Rosco CalColor Magenta 15 on my rimlight which works equally as well, if not better.

It's probably less necessary if you're shooting HD or a slower film stock since your image is probably already sharp enough to not give you any problems when you do your composite later.

Chris Keth · October 25, 2007

The way to not even need a magenta backlight and to avoid green spill is to have some separation between your subject and the greenscreen. If you're right up against the screen, you're pretty much guaranteed to get green spill and have trouble pulling a good matte.

John Brawley · October 25, 2007

I am lighting a puppet style character in front of a green screen. I heard from somebody that I needed a special gel to back-light the character to avoid the fake green screen look. Is this true? If so what is the gel called? Should the strength of the back-light be a stop higher or lower then the key light/s?

Hello there.

I had a shoot a few months ago that was along the same lines. Lately I've become a HUGE fan of the Kino greenscreen tubes (or bluescreen)

It's a pretty simple idea really. Use a regular Kino Flo fixture to light your bluescreen, then simple use the appropriate Kino tube. The colour is super saturated. It's crazy intense. I had a shoot with both minitures (where i wanted to light to F22) and a 60' long bluescreen for some live action with a man in a monster suit (with lot's of fur)

What was amazing was that once we put the Kino's up the lighting was very even across the entire 60'. Ive never been a fan of using gels in the backlight for seperation, because I think it entirely depends on what you're trying to comp in as a background....that has to motivate what's happening with the lighting.

With the Kino's you get a very intense and narrow spectrum of colour.

Check out the rest of the stills from the shoot....I used 12x4' Quads... Those are 1watt luxeon LED's in his eyeballs by the way...;-)

www.flickr.com/photos/johnbrawley/sets/72157600032568505/

Kino Tubes HERE

http://www.kinoflo.com/Kino%20Flo%20lamps/...s.htm#Bluegreen