I am finding I realy enjoy close up photography and have been considering getting a set of PB 6 bellows. However, I have questions. What are the differences between the PB 6 and the PB 5 or 4??? Will the PB 6 bellows work on the F3 HP or the FM? Will they work (mount) on the fuji S2? What is a good lens for close up work? I have a 35-70 manual zoom and a 50 and the Tamron 28-75 Di zoom. I am not looking at micrscopic work.. just closer than I can get with extension rings (I borrowed these once). thanks.