I didn't hink they'd changed the IS but I wasn't sure. Hmm your experience is different to mine then Hoppy. I got the corrupted image- sort of horizontal banding - a bit like venetian blinds, so I wasn't going to to take any further risks.
Sounds like you need a more stable Tripod.... or maybe not!
Seriously,
I dont think Gen 1 IS had auto tripod sensing?
The 100-400L manual says turn off the IS with a tripod, although it doesn't give any reason at all. On the other hand, The-Digital-Picture says:
"While the 100-400 L's IS system will detect a tripod and automatically disable itself, turning off IS when using a tripod will save a little battery life and cause the IS mechanism to be locked in a centered position." And while they don't get everything right on that site IMHO, that particular review has been up long enough for any mistakes to have been corrected long ago. Full review here
http://www.the-digital-picture.com/Reviews/Canon-EF-100-400mm-f-4.5-5.6-L-IS-USM-Lens-Review.aspx
I've just tried to upset the IS now. Tripod as solid as I can make it, IS just seems to park and sits minding its own business, whirring quietly. But if you introduce any movement, by raising the centre column for example, it works. With the lens at 400mm and on max magnification live view, you can see it clear as day. In short, I can't get it to misbehave on a tripod at all.
Apart from helping with shutter speeds, I find it really useful when trying to focus accurately with the centre point. If you want to nail the focus on the eye of a bird (as opposed to one of those fish you have in your barrel
) and with the tripod head loose, it's much harder to hold the position accurately with the IS on.
TBH I don't know why we are told to turn the IS off with a tripod, based on my experience with Canon lenses at least. Sure it shouldn't be necessary and it uses battery power, which probably is a problem if you are sitting waiting a long time in a hide or something, with a half press on the shutter release almost permanently (ie system active for minutes on end, even hours). But I can't see that it does any harm to the image, or even if it does have a hissy fit now and then, well the chances of that ruining a shot seem pretty rare. Of course I would turn it off if it actually did nothing on a tripod, but sometimes it very clearly does.
My other IS lenses, 70-200L 4 and 17-55 2.8, both much newer of course, simply say turn off the IS on a tripod to save battery power.
Edit: forgot to mention. Thought it was interesting that when I was trying to upset the IS by tapping the camera (up/down shift movement), the stabilising effect wasn't much. But it worked a treat when I tapped the end of the lens (rotational tilt movement). It's the shift movement that Canon's new Hybrid IS fixes, as fitted to the (very) new 100mm L macro.
Because the 100-400L is so long when set at 400mm, I guess there's a lot of leverage and tilt movement. Other long lenses too of course. But with shorter lenses when on a tripod there is perhaps more shift movement than tilt, so that regular non-Hybrid IS is going to be less effective anyway.
