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04-23-2021, 06:41 PM   #16
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It's because the mechanism for zooming relies on a guide that pushes the optics forwards quite sharply near 16mm. The force required to turn the ring normally pushes the link against the guide at a 60 degree angle near the 16mm point, and around 10 degrees elsewhere.

This means there is a huge amount of force on the link (stuff that is guided by the 'guides') and this causes failure of the plastic. Any play in the mechanism increases the force required to move it so stuff breaks inside.

It looks like an upside down Nike swoosh. The focus ring turning gives us the force to move along the swoosh. Going from 50 to 18 is much easier than 16 to 18 because of the gradient of the guide (swoosh).

04-25-2021, 07:18 AM   #17
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how smart is the design, on checking that plastic part to the metal guide is broken, the second plastic guide on the barrel screwed in is broken and now the screw does not fit, did a diy repair using epoxy, but doubtful but now in vain as,
in the process attempting to align two parts- barrel body to the focusing guide flex cable broke, my clumsiness, but it was minor clumsiness.
flimsy design, wonder how will it be rated in ifixit rating on repair-ability.
am sure its not engineering grade plastic which can take stress of bumps on the lens.
I strip lens repair them as hobby, but this is the lens which has tested my patience.
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