Hi folks, I searched but curiously (I know it was discussed quite a bit) I couldn't find a definite answer. It seems to me (from reading, never had this lens) that it's fine to leave IS on when you mount it on tripod. However, a friend of mine who has it and claims that with IS, sharpness and even the focus point are damaged. He used MLU and a cable release. http://d-spot.co.il/forum/index.php? showtopic=17341&hl=. I know you can't read Hebrew but you can look at the pictures. The top row is with IS on and the bottom row is with IS off. To sum it up, which are complete list of lenses which you should turn off IS when you are using a tripod? 75-300? 28-135? 100-400? Others? TIA. Happy shooting, Yakim.