I just received the 100-400. My camera is the XSi/450D. I did a few test shots and put the camera away with the lens attached. Next morning the battery was fully drained. Strange…perhaps I did not notice the level before putting away. Last night I put it away with near full charge an camera definitely off; next morning less than ½ charge.
I am going to leave it sit with a known full charge for a day or two just to make sure. But I am certain there is a problem. My other lenses are the 17-40 and 70-200 F4 IS. I don’t have an issue with either of them. I am always amazed long the battery lasts with both of those lenses and they certainly don’t drain the battery when the camera is off.
On the Canon website a reviewer had a similar problem (2nd review):
http://www.usa.canon.com …0_400mm_f_4_5_5_6l_is_usm
Curious if anyone has experienced this? I am planning returning the lens—I bought it from B&H. Now worried if I should forget about this lens and get the 400mm prime.
Thanks,
Jon

