Use of IS?

[DougBG]

For an example, given the following:
5D M2
Gitzo tripod with weight
Mirror lockup
cable release

For a variety of shooting condtions with Canon IS lenses, under what circumstances will IS be a disadvantage, if any?

[David Sutton]

If the IS is not of the type that senses when the camera is stationary and then switches itself off, then when you do a time exposure the image may drift and be blurred. I usually switch it off for long exposures just to be certain.
David

[feppe]

Every time you use a tripod.

[Geoff Wittig]

For an example, given the following:
5D M2
Gitzo tripod with weight
Mirror lockup
cable release

For a variety of shooting condtions with Canon IS lenses, under what circumstances will IS be a disadvantage, if any?

Depends on the lens. For very long lenses like the 500 f:4, IS is a godsend at any time, and greatly improves sharpness even on a tripod. For the elderly 100-400 zoom, you must turn IS off when it's tripod mounted because it gets confused and dances around. For a short lens like the 24-105 f:4 L, planting your rig on a solid tripod will gain you far more sharpness than IS ever will. I turn it off with this lens unless I'm hand-holding the camera.
Finally, I haven't really seen any advantage to using IS with the 70-200 f:2.8 when it's tripod mounted, unless I have the head loose and I'm tracking a moving subject, which is a pretty rare event.

[MichaelAlanBielat]

When I am out and about shooting a wedding or portrait job, I make sure that my IS is off unless I am in need of it.. I have had too many buddies burn out their IS mechanism on their lenses because they always kept it on... I also know from experience that IS can affect your image negatively if you have it enabled at very fast shutter speeds. I have gotten shots here and there that looked soft because I took the photo when the IS is in the process of moving around. I am not sure if that is the same with Nikon now but I learned to do those techniques on my Canon stuff and am carrying it over in the Nikon side of things as well. I just turn it on when I am in the 1/500" to 1/250" range and anything below that...

For landscapes then I have the IS activated for tripod shooting as others mentioned...

Hope that helps,
Mike