[quote name=\'Chief-O\' post=\'238520\' date=\'Mar 29 2010, 08:49 PM\']... Sometimes, the corners seem to be "vignetted" [the word us photographers use].[/quote]
I put an example on my blog:
http://quizproducer.blogspot.com/2010/03/c...erscanning.html. Is this what you're referring to?
I'll let the real old-timers correct me on this one, but it looks as if the round camera tubes (look up "image orthicon," "vidicon," or "plumbicon") were being over-scanned--the image you see actually extended beyond the round edges of the camera tubes.
Remember that when these shows were originally broadcast that perfectly rectangular picture tubes were years in the future (and no, I don't just mean color roundies). In addition, most sets were over-scanned so that the edges of the picture didn't show up on the home set.
It's not a video tape issue, it's a camera issue because you'll see other shots (taken with other cameras) in the same show will not have the same edge fringes and rounded edges.