I should amplify my comments. The rule of having a bellows at least 25-50%longer than your longest lens is for general work - landscape, portriats, etc. If you want to do closeup work down to 1:1) then your bellows does need to be twice as long as the lens you will be using for this work. (1`:1 is where the image on the gg is the same size as the object in front of the lens).

steve simmons