Hi, I hope you don't mind my jumping on the thread. Had my MK-C-UP yesterday, and spent some time trying various modes. 17-40L reversed gives good results at f22, but I am hoping to set it up for use with bellows and a 70-200L for bugs, butterflies etc with a ringlight (Yongnou YN14EX).
Here's my progress so far on coverting my vintage BPM bellows.
BPM 49mm reverse adapter to bellows.
The front from a Vivitar 19mm lens, which fits nicely onto the 49mm thread and offers a 62mm filter thread.
A 62mm to 58mm Step Down ring.
The 58mm Reverse adapter supplied by Meile.
This attaches very securely to the bellows, and I can still use the MK-C-UP for reverse lens work.
My problems lie on the other side of the bellows...the lens side.
Bellows connection is via BPM 55mm reverse adapter.
I have step-up and step-down rings, but cannot seem to get the thread size for the male connection that connects the two together to use as an auto extension tube. I could perhaps glue a step up or down adapter to the edge of the lens "blank" which is showing when the lens is reversed (if you see what I mean!) but I would rather have a proper threaded adapter than glue breaking and dropping my 70-200L!!! Do you know the size of the thread please, and is there perhaps an adapter ring I could utilise to attach to the other side of the bellows? Many thanks in advance. I thought the device would have EF bayonet connections throughout, which would have been easier.... Ty