I rented the 100-400 last week and I was amazed by the IS. I've even made a sharp picture handheld at 1/6th, but my keeperrate was 1 out of 100 I guess[:P] 1/30th of a second did very well for me. At 400mm of course, forgot to mention that. But those are all subjective to a lot of things. When I had the 1/6th shot is my subject was like 6,5-7m away and the short distance makes the IS function a lot better! Since the weather was amazingly foggy I didn't really made far away shots (I did, but they where rubbish in the nicest way), so I can't tell how good the IS was on further focus distances.


Anyway I was very pleased with the IS in the 100-400. Theoretically 2-stops perhaps, but I had a lot more. I'm also curious how this "2-stops" definition is made. Is there a particular standard? Focus distance (or subject-distance) plays a big role in my believe, so there should be some sort of test to determine the IS functionality. Or is it just a lot of shooting and taking averages?