Canon 100/2.8 IS Macro question

I am sure this has been asked before but I cannot find it - How effective is the I.S. when shooting at Macro distances?

Although the lens has a 4 stop I.S. I have heard that it is, in effect about 1 or 2 stops when shooting 1:1 How come?

Thanks in advance.

only received the lens today but my impression is that the IS works well for macro and will up your keeper rate for natural light hand held shots.

Apparently this lens + 7D in ai servo is rather amazing, I want to try it myself.

Roy C wrote in post #9958149
I am sure this has been asked before but I cannot find it - How effective is the I.S. when shooting at Macro distances?

Although the lens has a 4 stop I.S. I have heard that it is, in effect about 1 or 2 stops when shooting 1:1 How come?

Thanks in advance.

The only reason I can think of is simply the magnification factor. Camera shake is more obvious with a 600mm lens than say a 85mm and the same would be true with magnification associated with extreme closeups.

Exactly...
and the 100's IS works quite well.
Well worth the extra $ IMHO.

When I'm doing macro - even all my pet must be still. All it takes is my Bouvier getting up & walking around and it's a major shimmy & shake on screen -and that's even on a solid concrete floor!!!
My cat walking by and rubbing her tail against the display table leg is like an earthquake.

The IS is less useful at high magnifications.. but it does help when that little movement can be like an earthquake! and would help for street stuff near sunset when you need a handheld 1/30 shot

For me since I really only use my 100mm macro lens for macro work, the 100L with IS was useless as I pretty much always use my Canon Twin light flash and shoot at 1/200 anyway. You kinda have to use a flash of some sort to get those f/16 wide DOF shots, and if youre shooting at 1/200 IS really doesnt help that much.