I'm with Corran on that. By definition, a 120mm lens focal length lens focused at infinity is 120mm. Focusing on anything closer than that requires you to increase not decrease the bellows so something doesn't sound right. Here's some formulae you might want to look at on Kenneth Lee's web page.
http://www.kennethleegallery.com/html/tech/bellows.php
Using fl = 120mm and 1000mm focusing distance would result in a bellows draw of around 135mm if I'm doing the calculations right.
Hope this helps
Dave
(I'm assuming we're talking 4x5 cameras here. Getting full coverage on larger cameras with a 120mm lens might be an issue on some cameras)
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