Lens Rentals: Sony 135mm f/1.8 GM Tear Down

Lens Rentals has a Sony 135mm f/1.8 GM fail while it was in a clients hands, so when they received it back they decided to disassemble it to see what they found. This is the same lens that set records in their MTF testing so I’m sure it’s a popular one. Below are excerpts from the larger article with photos which you can see here:

  • The filter ring is well-engineered for cheap replacement in the even that the filter ring get dented and is heald in place with screws and slots that take a 1/8th turn to disengage.
  • The front also has a thick gasket, but they found out the back was the way to take the lens apart not from the front when they got to the gasket
  • The back has good weather sealing, but Lens Rentals has already had issues with dust inside multiple lenses
  • When they got the lens open they determined it was laid out logically and modularly, plus the build quality was robust
  • The focusing groups have a long travel distance that allows for precision and reduces aberrations
  • The first issue they found when disassembling the lense was that the front element of the front focusing group seemed to be poking up a little bit on one side, which could cause the lens to malfunction
  • The aperture blades are nice and smoothly circular
  • There is more weather sealing inside the lens beyond the front and back
  • When disassembling a lens everything has to be put back exactly where it came from so Lens rentals generally has to mark a lot, but the 135mm is assembled with these markings in place
  • The front element had the light shield pushed out of place in the end
  • The light shield caused a millimeter of tilt where 0.1mm would have been catastrophic
  • They were unable to fix the lens in this instance because it would take the removal of all the glue from the element and the repotting of the front element to fix
  • This was a one-off but other lenses have had dust issues
  • This is nothing to be concerned about and the failure was a wtf is happening kind of moment
  • This is a well-made lens with IS built like a tank and a robust magnesium alloy barrel that has lots of long thick screws holding it all together with nothing flimsy to be seen
  • The electromagnetic focusing motor is improved over the design a few years ago and is now built like a tank
  • Lots of care was taken engineering this lens and it shows from the layout to the materials used
  • The optical design is also well built too.

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Sony 135mm f/1.8 GM: B&H Photo / Amazon / Adorama


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