The Great 400mm Teardown Comparison: Sony 400mm f2.8 GM OSS vs Canon 400mm f/2.8L IS III

Lens rentals added some post to their teardown series for the new Sony 400mm f2.8 GM OSS and Canon 400mm f/2.8L IS III to see how Sony compares and it’s very lengthy. I covered all of the key points in the comparison below, but if you want to see the teardowns completely you will have to check the posts which I have linked too below. It’s a bit crazy to break down a lens at this price point, but lens rentals is the company with the confidence to do a proper disassembly.


  • Sony won the battle of most fluorite elements 3 to 2 over Canon
  • Canon has long been the one lens company that grows and polishes large fluorite in-house and Sony is using 3 large ones that might have been grown by Canon since other manufacturers generally make smaller ones.
  • Sony wanted them to tear down the lens because they thought lens rentals would be impressed and the lens is superb compared to the Canon but costs less.
  • Sony has a single pressure plate where the tripod foot mounts whereas Canon has a double so Canon’s mount is more robust.
  • The ring that the tripod rotates on is a similar design to Canon’s
  • Sony has a knob to click and declick the tripod collar ring and Canon requires disassembly to do.
  • Sony used good seals
  • Sony’s 40.5mm drop in filter might be more difficult to find than Canon’s 52mm
  • Sony uses flex from the bayonet electronics instead of soldered wires, which is a plus
  • Sony’s mount is heavy duty metal and is held in place by 7 screws instead of 4
  • No infinity shims in the mount or signs of a variable thickness mounts like Canon uses
  • Sony’s magnesium feels just like Canon’s
  • Sony uses small nylon gears to rotate the focus ring that has almost no pressure on them, but lens rentals isn’t a fan of nylon gears, so these shouldn’t wear out.
  •  Sony has it’s shims in the barrel and they can be accessed and adjusted, which if you’re going to use shims this is how you should use them.
  • The lens has markings by the shims that likely tells you how thick they are, which is nice
  • The flex runs throughout the lens are well run and secured there are even protective elements for the cables.
  • Sony’s focus ring has double sided tape on it’s covering whereas Canon’s is friction molded
  • Sony used a sensor shim to secure a cable under the focus ring, which kept them from having to design another part to hold it down, which is smart engineering.
  • Sony might allow for double centering with there shims, which Tamron used to do.
  • Double centering allows for a lot of adjustment and it can be difficult to get right
  • Sony’s new 4th generation LM is large and robust without using any glue.
  • Everything Lens Rentals found gave them confidence that the Sony 400mm f2.8 GM OSS is a solid lens and it’s comparable to other similar lenses from Canon/Nikon.
  • Canon is on their 8th generation lens and Sony their 1st and they already caught the gold standard

You can see the Sony 400mm f2.8 GM OSS teardown here and the Canon 400mm f/2.8L IS III teardown here.

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Sony 400mm f/2.8 FE: B&H Photo / AmazonAdorama
Sony a9 Action Shooting Kit: B&H Photo / Amazon / Adorama
Sony a9: B&H Photo / Amazon / Adorama

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