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Russell A.
Russell A., Camera and Video Technician
Category: Camera and Video
Satisfied Customers: 5227
Experience:  30 years of experience as a TV station technician gives me a unique understanding of technical equipment issues.
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how does a green screen work for weather broadcasting

Resolved Question:

how does a green screen work for weather broadcasting
Submitted: 3 years ago.
Category: Camera and Video
Expert:  Russell A. replied 3 years ago.
Hi

Since color in television camera have always used RGB (red, green & blue) light to produce color pictures, an effects generator is used to separate out a single color (presently green is used most often) and fill it with another picture source. This process is called Chroma Key. Since blue and green are technically the colors that are farthest from skin tone it is fairly simple to have the weather person to wear clothing that do not have the screen color allowing the Keyer to "cut out" the subject and insert the background image in the green area. Originally blue was used as the background color, but was changed to green as the technology evolved.


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Edited by Russell A on 10/6/2010 at 2:39 PM EST
Customer: replied 3 years ago.
Does that mean that a projected image ( like a weather map) is super imposed upon both the weatherman and the green screen?.
Expert:  Russell A. replied 3 years ago.
Technically, just the opposite. The image of the weatherman is super imposed on the image from another source ( like another camera, video tape or a map generator) the green is electronically rendered invisible.
Customer: replied 3 years ago.
Russ , when I view the Weatherman, is he/she looking at the Green Screen ? Does he/she see the map itself upon the green screen? When they stand "in front" of the Map are they just filtered out so that viewer doesn't see them?
Expert:  Russell A. replied 3 years ago.
No, there is no image projected onto the green screen. The weatherperson is looking at monitors mounted in a pedestal that are positioned at the far ends of the screen, that is why they have to practice pointing to areas when there is really nothing there.

Take a look at this video and the others on the page for a full explanation. I have used these to quickly train some technicians.

http://www.youtube.com/watch?v=w6brdwY-dvU



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Customer: replied 3 years ago.
I replied to you that I had viewed the videos and that you still have not adequately explained to me" exactly" how the weatherman is shown on TV superimposed on the map while pointing to various items on the map. I also asked you if you had videos showing the phenomenon. I have not jet recieved a reply. Please reply to this e-mail when you are able to do so
Expert:  Russell A. replied 3 years ago.
Sorry for the delay, your last message was never received. Unfortunately, I do not personally have videos showing what I assume to be multiple angles of this process. Also, are you looking for a technical explanation of how the Chroma Keyer actually mixes the two video sources together?
Customer: replied 3 years ago.
What two video sources? Is one of the weather map and the other of the weatherman? I really want a layman's explanation of what I am seeing on TV, when I watch the weather. If you think the technical explanation would help-yes
Expert:  Russell A. replied 3 years ago.
Yes, one video source is the camera shooting the weatherman and the other video source is the picture of the weather map. The two pieces are completely separate, they are combined electronically in an effects generator called a chroma keyer. See below

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Russell A., Camera and Video Technician
Category: Camera and Video
Satisfied Customers: 5227
Experience: 30 years of experience as a TV station technician gives me a unique understanding of technical equipment issues.
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