scyrene said:
Haha my arms are weak too, but you get used to using these lenses, right?
On a serious note, is there any data on AF with/without IS? I don't find it interferes at all, but I've not tested it. Has anyone? Incidentally, determining the 'keeper rate' advantage with IS would require more than 4 shots...
Firstly please note that I am a bit Anti IS, but that is only because I have lenses that have it.
As to data - I suspect not. There are probably too many variables to get any valid conclusions. I can however give you one example of my data. Visited the Red Kite center at Llandeusant (don't you love Welsh spellings!) and used my (then) Canon 300 F4 L IS - 300 frames and not a single keeper. I re-visited the following weekend, turned IS off = a couple of hundred good shots and 100 + potential keepers. This got me thinking to say the least!
Later, when I had my Canon 600 F4 L IS, I found the same thing though not as pronounced. I also observed that AF acquisition was a touch faster, we are not talking night and day here just that split second that may get you a shot. Later again I sold the 600 and went to the Canon 800 F5.6 L IS with it's 4 stop IS system. The new IS allowed hand held shots at 1/125 sec - wonderful I thought. However the lens didn't track too well on my 1D4 and 1DX and could be a (very) little hesitant to lock on to a subject. Going on my previous experiences I tried it with the IS off. It now focused faster and tracked better than my 600 and rivaled my Canon 300 F2.8 L IS (with IS off) for AF = happy me! I now haven't used IS for 2 years and 5 months - I wonder if it still works? ;D
Naturally there is a downside, namely higher shutter speeds are needed when hand holding or shooting partially supported (ie no tripod or mono pod). 1/125 sec is now no longer practical with my 800mm but 1/250 sec gives a high percentage of good shots hand held.
Not using IS will not suit everybody, I haven't met them yet but they must be out there? All I would suggest is that you and others give it a go and see what happens. I (and some local photogs) have found a significant increase in our hit rate by doing this. After all if it doesn't work for you then you can always turn it back on?