Just received the 12-40, what a beaut. Veeery strange, the first couple of times I assembled it to the the camera it went bananas. Controls had a mind of their own, it was AF'ing and beeping by itself, my finger no where near the shutter button. Please don't ask for specifics, it all happened too quick, I removed the battery, seems to be OK now. Just as an aside, much prefer the combo without the grip, it's faaaaaaaaaaar to big a lump with it.