You haven't followed all of the history of this lens. It was released for Canon mount first and had problems with the APS-C cameras. Tamron was aware of the problem and pulled the cameras from the shelves to supposedly fix this problem. They released the lens without fixing the ones they had pulled. They then released a Nikon mount.

Tamron announced they had corrected the problem with the canons but you had to send the lens back to get a firmware update on the lens itself. You can not go by the serial numbers, because many of the later released lenses still had problems. The only way you can be sure is to send it back to Tamron yourself.

Since we are discussing Canon cameras and the Canon mount lens, not Nikon, your comment has nothing to do with this thread.

Jim D

Hello fellow hedgehogs! Was thrilled when I got my 7D mark ii which is a phenominal camera and works well with most of my lenses however.....when using my Tamron 150-600 anything at a distance whether it is a bird or a tree it is having locking on issues. The lens or if if it is the camera just wants to keep hunting so maybe you get a clean shot (when you do it is great!) but most times it just keep hunting even though the camera says it is focused. Thought it was the camera as I was not having this issue with the 7d. I returned the camera and it is having the same issue. Anything rather close their is no problem. Anyone else having this issue. I'm think I saw an update 2 today or yesterday. Any ideas? If this is inherent I may just sell the lens and just use a 1.4 or 2x extender on one of my L lenses. All advice appreciated! Thanks in advance! Just for clarification I returnednthe first mark ii and did get another one which is having the same issue so my guess is that it is the lens. Thanks again!