Hi All, This is a continuation of my DYI thread started here to modify Rodenstock TV-Heligon 50mm f/0.75 for Nikon. But this time I made it focus and added AIS aperture (for those non Nikon folks - AIS allows keeping aperture fully open during framing but then stops it down to selected one when shooting). Having acquired a new Rodenstock TV-Heligon 50mm F/0.75 lens (which incidentally is brand new - never been used whict in itself seems to be rarity) I now made the initial modifications to allow it to be mounted on Nikon F mount with limited focusing and full aperture control. As the first time, the lens came from the same source (Adam Bexley at Abex UK) and I would recommend to use Adam's help if you are after the lens like this one. The focusing part is removable and the lens can be used in the same way as my first conversion as well. To achieve this, the basis of conversion was to attach the 72mm to 52mm step down ring to the base of the lens which then makes it possible to mount various 52mm threded attachments. The BR-2A reverse mounting ring (next to lens on the photo above) can then be screwed in to give the same type of convesrion as my first lens (only making it slightly shallower which increases the working distance for the lens a bit). The photo below shows this configuration: The stepdown ring was glued to the lens backside the same way as before with Araldite epoxy for metals. I will reinforce it with screws in a future when I find the right sized tap. And a closeup of this (step down ring is black one in the middle): To allow the limited focusing and aperture control, I used an old Nikon E-Series 50mm F/1.8 lens which is relatively flat (nearly a pancake lens). Using something like 45mm GN Nikkor (a proper pancake lens) would have been better since it would allow closer mounting to the lens rear element but those lenses nowadays are ridiculously expensive so it is out of the question for me. The Nikon lens had all the glass and some frontal parts removed. I left the diaphragm assembly, lens mountg and helicoid intact. For the first implementation (proof of concept), I also left the filter thread there and use a 52mm reverse coupling ring to attach that to the Rodenstock lens. This is how the modified Nikon E-Series looks with the coupling ring and fully extended helicoid: And a view from the top: The beauty of having the full lens to play with is that the diaphragm part is working as it is on a normal lens - i.e. it is fully opened when composing but pressing the shutter closes it down to the selected aperture value. This also makes DOF possible which is nice to have feature with this lens. The aperture selected by the aperture ring and for this lens ranges from F/1.8 to F/22. Considering that the lens is mounted further from its optimal position those values are just about right. This is how the whole lens looks when assembled: And on a D200 camera: I still have a problem with this design, the diaphragm is a bit further from the lens back element so it is not in its optimal position. I will eventually reconstruct the mounting 52mm thread and get rid of the filter ring and coupling adapter altogether. This though will be in a future as I am still wating on some parts and will need to experiment. For sample images please see followup message - due to limit it was not fitting in one message. Any comments, questions - please do ask.