Boyd Ostroff |
March 14th, 2009 09:12 AM |
Quote:
Originally Posted by Adam Gold
(Post 1025517)
I think we were geting confused over terminology.
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Indeed! allscan=underscan, not overscan. It may help to understand if you consider the origin of these terms. With CRT tubes, an electron beam is deflected left and right across the face of the tube where it lights up the phosphor and creates an image. Standard TV sets were designed to overscan, meaning that the electron beam actually scanned past the left and right edge of the tube, and the portion of the image contained in that area beyond the tube edges was not visible. This was done because there could be ugly artifacts on the edges of the image, and there might also be things like mikes or lights accidentally in the frame.
Now professional CRT monitors could underscan, which means that the electron beam did not sweep quite as far as the left and right edge of the picture tube face. This would show the entire image, warts and all, and leave a little black border to the left and right past the scanned area.
Most consumer camcorders have viewfinders which overscan, meaning that you cannot see all the way to the edge of the image. Until very recently, almost all regular TV's also overscanned. In fact, I have several LCD TV's, and only my newest Sony Bravia has a menu option to show the entire frame.
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