Green Screen
What is green
screen? A basic answer is having talent stand in front of a
green screen and then use a device (hardware or software) to remove
that color and replace it with another image or video source. This
gives the illusion of the person being somewhere else, and it's
a more common technique than you might realize. Not only is the
weather man being keyed in front of a green screen, but more and
more often field correspondents and even newscasters are green screened
into virtual sets. Sometimes green screen is also called chromakeying,
more general term which covers keying on many colors including blue
and red. Green screen is commonly used when control of what the
talent wears is out of the producers hands (in a field environment
perhaps), because people tend to wear more chrominant blue than
green making green screen ideal for mobile chroma key. Green screen
tends to yield a less attractive spill, because green screen backdrops
reflect more candela the spill off of a green screen backdrop will
be brighter and more noticeable than a blue screen backdrop.
Green Screen Backdrops
Getting a even color behind the talent is the first step in a good
chromakey, this usually requires a green screen backdrop in the
form of cloth or paint. Some green screen paint can be picked up
at hardware stores or lighting places like Studio Depot (Burbank,
Ca), blue cloth can also be found many places. Some companies sell
green screen pop up green screen backdrops which travel easily and
popup like a windshield shade.
Another alternative to green
screen is Chromatte,
a unique retroreflective material which is gray to the eye, requires
little or no light, and casts no spill on the talent because the
material is gray to the naked eye. But to the camera it sees it
as a perfect blue or green. This is because of the Litering,
a ring of LEDs around the lens which casts blue or green light onto
the Chromatte material. Chromatte is also very portable in the form
of a Chromaflex,
a 7x7 popup which folds down into a 3 foot hoop. Chromatte is superior
to green screen in many ways.
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