Originally posted by Buddha Jones
To make a 50mm Macro go from 1:2 to 1:1, do I need 50mm worth of tubes?
Buddha, to take a 1:2 lens to 1:1, you need additional extension of half the focal length of the lens. 1:1 means that the lens has extension of exactly the same amount as the lens' focal length. If the lens already has enough extension to get to 1:2, it has half its focal length in the focusing helical, and you need another half.
My M 100mm macro uses a 50mm tube to switch the range to between 1:2 and 1:1 from infinity to 1:2.