I've been inattentive to the forum for 8 or 9 months; just busy you know...
I wanted to share something I just made, with a simple recipe that anyone can replicate.
First some teaser pics:
With the Hartblei RZ67-645 adapter project still apparently stalled (and baulking at the proposed price even if it were available), and just wanting to have a go myself, I made my own.
Parts you will need:
Clockwise from the left:
(1) Camera with Mamiya 645AF mount,
(2) Mamiya RS-58 reversing ring (normally for reverse-mounting a lens on an old manual focus M645 macro bellows)
(3) 17mm-31mm M58 helicoid tube (ebay Item ID: 301497472003)
(4) RB67 ProSD (or similar) rear lens cap [note that the middle has already been cored out in this photo]
(5) Sacrificial 58mm filter (the glass is discarded, so any old scratched filter will do, as long as it has female threads for filter/hood stacking)
(6) RZ67 or RB67 lens.
I had the camera and lens already (I have no RZ camera, but the RZ 110/2.8 lens had been used in a scientific instrument 15 years ago).
I used an old unwanted Tiffen Skylight filter for part (5).
I bought parts (2), (3) and (4) on ebay (£10, £44, and $15, for a total of under €100 shipped to me).
First I got the reversing ring and the lens cap, and then based on their measured depths and the published flange distances for the Mamiya 645 and RZ67, I knew that the 17mm-31mm tube would comfortably cover focusing to infinity.
There are three parts [2, 4 and 5 in the list above] which require some machining work.
It is important to appreciate that no precision is required in any of the machining. We are merely removing excess material from parts which are already perfectly fitting! This is why I say that anyone can DIY it with fairly basic tools and know-how.
The RS-58mm ring can be found fairly readily and cheaply online. It is a large disc designed to fit the front of the old M645 bellows, and as such it is much too wide for the old M645 camera bayonet, and slightly too wide for the 645AF camera bayonet. A few mm needs to be shaved off its outer perimeter, so that it is about the same diameter as the shiny flat part of the camera bayonet. As the pic shows, I shaved off slightly more than that - like I said, precision doesn't matter. I got a machinist colleague to do this part nicely and fast.
The helicoid tube screws directly onto the RS-58mm ring.
The next step is to core out a hole centred in the rear lens cap, big enough for the M58 threads of the helicoid to pass through cleanly. I did this myself with an adjustable coring bit on my standard electric drill. The RB67 ProSD caps are made of a thick, stiff plastic (good for rigidity!) but plastic cuts easier than even wood. It doesn't matter if you are cosmetically sloppy and scratch or scuff around the hole, as this will be covered out of view for the most part in the finished product.
Now we work on the 58mm filter. Remove the retaining ring/clip and the glass. You won't need either of these again. We only want to use the outer frame as a locking ring. Nearly all filter frames are a few mm too deep for this project (they would press against the ~60mm collar protecting the rear lens group) so this is the final bit of machining to do. [You could use a "slim" 58mm filter to minimize the machining]. Reduce the depth of the ring by removing material from the *lens* side - completely remove its male threads (we will be using its front female threads). By trial and error I found the amount I needed to shave off so that when the adapter was assembled, I was able to close the breech lock on the lens over it. You can be really sloppy - I was impatient and just Dremel-sanded off more and more of the ring's soft aluminium. The result looks irregular and atrocious but this will never be seen inside the adapter!
Finish off by cutting a couple of notches on either side of the ring, for a spanner wrench to grip:
Push the helicoid thread through the cored-out lens cap and thread the shaved-down filter ring on the other side to keep it in place. Use a spanner wrench on the notches you cut in the filter ring to lock it tight. (If you later desire to set a particular lens orientation, loosen the ring slightly, rotate the tube, and tighten again).
The finished adapter, viewed from the lens side:
This pic shows that the choice of the M58 filter as a locking ring, rather than something wider, means that you don't need to core out the ~60mm diameter "collar" protruding on the inside of the lens cap. Retaining this helps to make the whole adapter more rigid.
The finished adapter, viewed from the side:
The finished adapter on the lens, viewed from the camera side:
Incidentally, this pic also shows another reason why I chose 58mm/M58 as the standard diameter for this project. It is the largest "hole" which fits inside the lugs of the Mamiya bayonet. There are also 52mm and 65mm helicoids available, and even an off-the-shelf M52 to Mamiya bayonet adapter, but they are undersized and oversized respectively.
The whole assembly on the camera, focused to its max and min positions:
The breech-lock on the RZ67's lenses holds the adapter on absolutely securely. I trust this far more than my commercial adapters of regular bayonet-mount lenses to smaller-format cameras.
Used with a 10mm Mamiya extension tube, for the close focusing range [headshots etc.]
Last thing to mention: what about the shutter and aperture controls on the lens? Well I leave the lens cocked and hence the shutter open, and a small strip of duct-tape is holding the DOF preview lever back, so that whatever aperture is set on the lens, is immediately implemented. This suits me as I nearly always shoot at f5.6 and faster. If you're an f/22 kind of person, you may seek some better solution.