The Tamron 17-50 has an issue. It sometimes doesn’t think that it is attached. I will be shooting pictures, when it will just stop auto focusing. Sometimes if I turn it off and then on, it will say the lens is not attached. That just doesn’t seem good. It was really sharp though. I was tempted not to send it back it seemed so sharp. I have a new one coming, and hopefully it will be just as sharp.