Hello! I'm new to both this forum and to large format photography, but I have a new lens and figured this would be the place to learn about it.
I went on a trip last weekend to the nearest city (300km / 4.5h drive), and while there, I was rummaging through a second hand store. Underneath some furniture and an old accordion(!), I discovered a huge lens with a very vintage & homemade looking brass M42 adapter.
The lens has a number of markings on it which, with the help of Google (many of the search results ending up here), have helped me get a rough idea of its origins:
Apparently the J.H.D. stamp and the UU serial number both signify that it is a design/product of the John Henry Dallmeyer company, while the A.M. and the arrow signify that it was built for the UK Air Ministry for use as an aerial photography lens, possibly in the WWII timeframe. Supposedly the "14A" is a design or category, while "3140" is the military contract under which the lens was produced.
The lens itself is quite heavy, and has a large aperture ring that stands out from the lens body. There is a brass block bolted to the ring, perhaps to couple the ring to a cable or some other mechanism? The lens mount threads are ~75mm in diameter, and the filter threads are the same.
The iris diaphragm has 20 blades, which completely disappear when wide open, and become reasonably small when stopped down. Several parts of the front lens ring, aperture ring, and lens body have been painted over and re-etched with different numbers, so I believe this lens started out as a "14in f/5.6", but has now been relabeled to "356mm f/4". The factory aperture markings seemed to have ranged from f/5.6 to f/16, while the hand-engraved numbers range from f/4 to f/11.
I held the lens up to the window with the curtains drawn around it, and by holding a piece of paper up behind it, the infinity focus point seems to be around 80mm behind the M42 flange of the adapter. Since neither the lens nor the adapter have provisions for focusing, my only conclusion is that this was designed to have a bellows or variable extension tube inserted between the adapter and a camera body.
Without the adapter, this lens has a huge image circle. Our estimates with the sheet of paper put it a bit short of two A4 lengths in diameter when focused at infinity... so something like 50cm? I could be wrong, but I think this puts it in "ultra large format" territory?
That's about all I know. Like I said, I'm completely new, so please correct me if anything is incorrect, and let me know if you have any other insight into what this lens was designed for, or what it could be used for.
Thanks!
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