Ouch, I just found a problem with my Tamron. While it is mounted on 5D MK III, and camera is switch off, there is a huge battery drain. I did a few tests and found that it is caused by the Tamron. What a bummer. Started googling and found some threads about it on internet. Someone claimed it does not happen with lenses serialnumber 02xxxx. I have xx6xxx. I guess I will have to sent it to the servicecenter to fix it. I have read Tamron is aware of the problem and is able to fix it. I hate buying something and then have to return it for a fix. Does anyone have experience with the Servicecenter of Tamron? I hate to have something fixed and then being introduced with a new problem.