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Chroma-Key Answer
Mon Dec 01, 2003
Listen in RealAudio 
Welcome to December! It's the beginning of the month, and time to answer last month's
Brainstorm. Hi, I'm Bryan Yeaton, and this is The Weather Notebook. Our question last month
centered on the technology that allows your weather forecaster to point at a map that exists
only in a computer. Here's a call from Colorado Springs: Hi this is Lesley Lygon. It's called
a green screen and the map is actually on the monitor. It's not even behind the weather
person at all.
Jeff Liflich of Bloomington, Indiana fills in some details. I'm calling to answer the
question about the map on the wall, called chroma-key. It works by computer seeing all the
colors green or blue and adding the image to only those colors behind you.
My name is Bill Pierce, from Burlington, Ontario. The weathercasters are actually standing in
front of a blue screen and, the chroma-key filters out the blue and substitutes the weather
map for anything blue in the back of the weather caster so that's how they are able to
superimpose the weather map behind the weathercaster. A little bit of T.V. trickery.
Hi my name is Tricia Peasley. I used to do the weather for a little TV station in Alaska.
That's how I found out.
For Richard Lord of Durham, NH, chroma-key technology provides unexpected amusement: If the
weather forecaster happens to wear a blue neck tie then suddenly you'll be able to see through
him to the weather map.
Actually, several listeners mentioned this, like Carl Keating, who listens on Nashville Public
Radio, it's usually pretty entertaining to watch the weather scroll across a neck tie or a
jacket.
Thanks to all who called in! Our show is funded by Subaru and The National Science Foundation.
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