 Chroma
Key Usage:
When you watch the weather man (or woman) on the TV the background graphic
is combined with the talent in a video mixer. The talent is actually
standing in front of a Chroma Key green painted wall and the video mixer
substitutes the graphic for the green background.
Chroma Key (also referred to as Green Screen)
is used extensively in movie making today, with some films shot almost
entirely with actors in studios painted green. Movie examples:
300;
Mystery Science Theater 3000
Chroma Key is also being used
in some portrait studios or photo kiosks in malls to allow the customer to
select a digital background from a gallery of choices. This process is
structured around a software application that facilitates the compositing
process. |
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Lighting a Chroma Key
background is all about even consistent illumination across the entire
background. The more consistent the illumination the less difficulty in
"keying in" (substituting) the background.
-
Paper is easier to light
because it is essentially flat
-
Fabric, when stored in a
bag, is wrinkled and must be stretched or steamed or both to remove the
wrinkles; the flatter the surface of the background, the more consistent
the illumination will be and the keying results will be improved. Fabric
can be very difficult to get perfectly flat.
In most situations using 4
lights on the background will produce the best results. Position each light
to radiate from a corner to the center of the background. Move the lights
away from the background until a very even illumination is produced. Also,
position the talent so that none of the background lights are interrupted
to produce a shadow on the background. |
