Yesterday my Sigma 150mm (OS version) started to behave strange... the viewfinder image started to jump up by at least 40-50% and when OS is activated the AF-ON focusing only works the first time then if you want to keep the OS activated but change focus object then it won't focus but the viewfinder shows the Red color as the camera system tries to focus.
Also when the OS is OFF then the focus is 100% but now when the OS is on then it starts to backfocus. Activating/deactivating OS createst a clunk sound and you can really feel that something is shaking the barel.
Has anyone experienced this problem with this lens or another Sigma lens with OS?
WTF! The dealer called me today and told me that there were nothing wrong with the lens. Couldn't believe it but I went to pick it up. I of course tried it and to my amazement that clunk sound was gone and it seemed to respond to AF-ON and refocus when the camera was on AF-C however to refocus in AF-S mode I need to deactivate and reactivate the OS.
So it seems to work ok so I will see what happens before deciding wether I should send it to Sigma for servicing or not. That would probably mean 1 month downtime for that lens.