Went out for a fun evening a few weeks back with this lens. Tried some "night" stuff...
---------- Post added 02-10-2017 at 12:33 PM ----------
Lens update:
As previously noted I deployed a very DIY focussing system for this lens. The body of the lens was inserted into a Sony E mount three extension tube set with the actual lens body wrapped in black velvet that had an adhesive backing. This acted as a primitive focussing system. It was ok but after some time the primitiveness began to bug me.
What to do? The goofy thread on the barrel of the projection lens did not match any lens thread system I know of. I tried a few things and then found eventual success. I bought a M52 - M42 focussing helicoid adapter. I hoped the lens would fit into the M52 end. I also bought a super thin M42 - Sony E mount adapter to go on the back end of the focussing helicoid adapter.
Problem: the threaded body of the lens was just a bit too thick in diameter to fit into the focussing helicoid adapter. I thought about grinding off all the threads on the lens myself but that would mean removing a couple of inches of material. Doing that evenly with a grinder or Dremel tool was not appetizing. I then went wondering down into a part of town that had boat yards and a couple of machine shops. I found a small enthusiastic shop. After looking at the focussing helicoid adapter and the lens we decided to remove some of the inner material of the focussing helicoid adapter itself rather than touch the lens. This had to be done carefully so as not to remove too much of the inner focussing helicoid adapter which might make the back of the lens recede too far into the camera.
The shop did a great job. The lens now fits into the focussing helicoid adapter just perfectly. I can now get really close focus plus infinity focus. To make sure the lens stayed secure I added some silicone to the machined section of the focussing helicoid adapter. I also added a rubber O-ring to the back end of the system to help keep moisture out and make it it look more polished.
Bonus: I found that I could unscrew the ugly front threaded ring on the projector lens and substitute two of the threaded extension tube sections. This helps keep everything snug and tight and looking good!
The lens now focuses more easily and accurately. The focussing helicoid adapter is not as smooth as a real high end lens but it is certainly good enough for this project.
I thought about adding some kind of aperture system but quickly abandoned that idea: the fun part of this venture is the fast f/1.2 fixed aperture.
Here is how the lens looks now...
Some closeup tests (that little car is tiny)...