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It looks like the rear element is recessed a couple mm below the the bottom thread of the lens mount, so I'd probably have to either file down the rear barrel (it's big so it would be a lot of work) or get one of those lens spanner tools to pull it out to reset it. I also discovered the front of the barrel is every so slightly dented, rendering the filter thread unusable, so I would need another tool to fix that. At this point the tools to fix it would surpass the $20 I paid for the lens. My Sch