I've owned this lens for about 3 years now, and the problem has finally caught up with me. This is a well known problem and is documented on the internet. Basically, the focusing mechanism starts to fail and not allow the ring to work at the extreme ends of the range. AF just goes back and forth as it tries to get to a spot that the ring won't allow. The problem seems to be due to a helicoid that becomes misshapen. There is a rather detailed DIY fix
that seems to be fairly straightforward with good photos and appropriate warnings along the way. I actually came across it about 2 years ago and saved it to Evernote
, thinking it might come in handy some day. That some day is here.
Before I dive into it, does anybody have any other experience this problem? Am I better off to send it to the repair shop? Thanks in advance for whatever insights you have.