How Does Green Screen Work?

Setting Up Lights For A Green Screen Shot

Comments

Great article

Really nice article--wish I'd read it years ago, when I first started doing green screen work.

 

The "Light it Evenly" and "Light it Separately" sections are particularly important to getting an easy key. I use 48" fluorescent tubes to light my screen--two banks of two, one on the left, and one on the right. It gives a nice even light vertically, and it's pretty easy to position the lights so that the screen is evenly lit from side to side.

 

The tubes are color-balanced to 5000K, which makes them a good match for the fluorescent softboxes I use to light talent. I use a black shop-light fixture from Lowes to hold the lights--black doesn't cause any stray reflections from the talent lights. I sprayed the inside of the shop lights silver to increase the light output, and I use a simple Mannfroto light stand adapter to mount each light on a light stand. It only takes about five minutes to set up the green screen lighting.

 

Green-screen fabric works very well--much better than vinyl, which reflects light, and easier to work with than paper. People complain about having to iron out creases and wrinkles from the fabric, but it's really not necessary. Hang the fabric from a backdrop stand, and use small clamps to attach the fabric to the top and both sides of the stand. You can easily stretch it taut enough to remove any wrinkles and creases, and it should produce a very even key that requires no manipulation in post, other than simply pulling the key.

 

Thanks again for the article!

I use an unconventional

Len Vine's picture

I use an unconventional method to produce green screen.

Back in 2000, there was a system called Holoset, by Play, which consisted of a highly reflective silverized type of screen, and an LED ringlight that fitted over the camcorder lens, which, with an adjustable controller, allowed you to dial in the required intensity of green screen

The main advantage of this system is that it doesn't require an absolutey evenly lit screen, with lots of lght on it, like conventional green screen setups do.

The Holoset company went out of business a few yearss ago, but perhaps someone else has taken over the business.

I still use the system to this day, and it works perfectly.

 

Len Vine

Why "Green" Explanation

FrankC's picture

The choice of the color Green was more because of the change over from analog video to digital video.  Blue was first chosen because it is 180 degrees (on the color wheel) opposite most skin tones.  When video changed to a digital process, Green was chosen because of how colors were sampled.  Not all available information was sampled on the Red channel or the Blue channel.  If you're going to do a Key special effect process, you want to do it on the channel where you have the most sampled information to work with... that was the Green channel.