You have left out one important detail. What format are you trying to cover? There are a number of "Tele" type lenses that will cover 4X5 and require less than the focal lenght to get infinity focus. However as you move up in format, the number of "Tele" choices gets much smaller. The 24" Artar is about 600mm focal lenght and does in fact require 24" of bellows extension for infinity focus. Fuji makes or made both a 400mm and a 600mm Tele and Nikon made 500mm, 600mm and 720mm Tele type lenses all of these lenses will give infinity focus at approximately 2/3 of their focal lenght.