Sigma 120-300mm f2.8 DG OS Focus Issue
Hi, I'm a keen willife photographer and own a Canon 7D with various lenses including the 100-400 f4.5 - 5.6. I purchased the Sigma lens because I really wanted a faster lens for early morning/evening shots and with it being a zoom its very versatile. The problem I have is as follows. When I angle the lens more than 45 deg upwards the auto focus stops working, its as if the weight of the internal element is slipping somehow. Then I tried the manual focus ring and the same thing happens, when I try to focus from min to infinity the internal focus element just slips without any change, when I look at the distance indicator through the window it stays in the same place. Has anyone had a similar experience because when I phoned Sigma they said this is the first time they've heard of it.