I’ve partially disassembled my Mitakon II 35mm F0.95 week ago.
At the first attempt I didn’t discover how to move further with disassembly to reach aperture area, so assembled it back.
Few observations:
Parts inside look a bit unfinished, with sharp edges and metal cut signs.
Mount ring is heavy. Looks like it’s brass alloy inside. It’s secured with 3 long but thin screws.
Rear lens is firmly attached to the lens mount ring, even some glue is used.
Outer helicoid part made of quite thick aluminum.
Black ring with DOF scale can be put in any position, so if your sample has it rotated, it’s easy to put the ring back.
Aperture ring is very loose on my ZSM sample. It has same surface as focus ring, so I often accidentally touch it and rotating instead of focus. I’d be happy to have it very stiff out of the box, or have “clicks” there.
As a workaround I simply put wide rubber ring (piece cut from bicycle tire pipe), so the rubber ring border firmly grips aperture ring, and it rotates with more effort now : )
From what I see there is a lot of grease, and all helicoid parts look like made of aluminum or aluminum alloy. I think they should work fine in cold conditions.
Update: Frozen to about -20 Celsius, this ZSM 35mm has more stiff focus ring rotation, however it’s large diameter keeps it still comfort enough.
What I liked is the aperture ring stiffness – it is rotating like focus ring in normal room temperature.
NOTE: if you decide to repeat such fridge experiment with any lens, make sure it’s packed in ziplock first with minimum of air inside. I did so to prevent condensing moisture on lens surfaces and body (and possibly inner glass), and only unlocked plastic bag after lens warmed up to room temperature.
UPDATE (Aug 04 2018): Mitakon 25mm F0.95 has very similar assembly design of the rear lens area. You can use following guide for more details: Disassembly of Mitakon 25mm F0.95 Speedmaster lens
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