This happened to me a couple weeks ago, I put my new Tamron's 90/2.8 rear cap on my Sigma 10-20, and now I've been unsuccessfully trying to get it off every now and then for the past two weeks. Luckily the 10-20 is the lens I use the least of late, but it's still incredibly frustrating. Terrible design by Tamron (this is my first Tamron lens, and my first time putting its rear cap on another lens).
Bumping this to show that this problem is still a thing over a decade later.
Originally posted by sac 
and eventually after 15 mins of jiggling, squeezing at different points, pressing(cursing) it came off with only tiny bits of plastic filings around the lugs
This ended up being my experience after posting this earlier. I've been mixing my Pentax and Sigma's rear caps with no issues for over a decade now, but I guess I'll be keeping the Tamron's rear cap for just that lens, lesson learned.
Last edited by pentakkusu; 10-17-2020 at 06:15 PM.
Similar Threads 
