Disassembly – Carl ZEISS Planar T* 50mm F2 ZM lens

Most of Zeiss ZM lens are quite compact and solidly built and work flawlessly for long period of time. The 50mm F2 Planar may only need disassembly for cleaning dust or re-lubrication. However sometimes you may also want to calibrate the infinity focus point on Leica M body.

Fortunately disassembling ZM 50mm F2 Planar is quite simple process, though it requires precision and some precaution steps.

Tools required:

  • Spanner wrench
  • Rubber gloves
  • Air blower
  • Precise tweezers

First step is precautional to protect the rear lens from accidental scratches. I’d recommend to cover rear lens with cut round piece of clean lens wiping tissue. Spanner wrench will be located very close to the glass.

Then you put lens with rear side up. and use spanner wrench to unscrew CCW the ring around the rear glass element. Typically I carefully unsecure the ring and then hold the wrench stable and rotating the lens body around it until ring is unscrewed and becomes loose. Make sure wrench blades don’t touch the outer sides black coating.

Then you simply pull the rear lens body up, that consists of mount and focusing helicoid assembly. Please point attention at the helicoid connecting bolt location when assebling the lens back, it should fit to the corresponding helicoid slot.

There are number of shims located right under the helicoid connector. They may have different thickness to compose precise distance for exact infinity focus calibration. Once I’ve fine-tuned another Zeiss 50mm F2 sample for Leica M240 by simply cutting extra one shim from thin aluminum sheet.

Each calibration shim has rectangular slot area, so you can rotate that slot to the helicoid connecting bolt position and easily remove it without unscrewing that bolt.

Next step is to gently unscrew CCW the whole rear lens elements assembly and get acces to the aperture chamber. Typically most annoying dust appears there, because all other air areas between lens are sealed by their frame. Please note that there is another set of shims there for calibration.

Once the rear lens elements assembly is extracted simply ise air blower to remove the dust from aperture chamber (with wide open aperture position) and from inner glass surface of extracted frame. Close aperture to check that there are no dust there.

I also use strong LED light to check the glass after cleaning and assembling the rear glass. Minor amount of small dust particles is accepted, they may be there even right out of the factory and it’s fine.

Once the rear glass is tightly screwed CW back, put the focus+mount part back by fitiing position of focus helicoid bolt, then carefully screw back CW the securing ring.

UPDATE: Just in case you need to disassemble Planar 50mm F2 from the front (I skipped it during initial disassembly) the first step is to unscrew CCW front metal ring with letters. Then you can use rubber glove or spanner wrench to unscrew CCW whole front glass elements assembly.