Originally posted by mattdm You mean because the camera moves that much away from the subject? I think that'd only come into play of your shake is on the order of an inch or more.
I think Z axis movement of the camera would produce the least affect on focus, when compaired to either X or Y movement. You are right, unless your DOF is very shallow, the camera would need to move a distance greater then the sensor could compensate before Z axis SR would be useful.
But, camera rotation on the X and the Y axis would cause image blur as easily as movement along X & Y.
And you cannot compensate for X/Y yaw without allowing the sensor to move on the Z axis. A simple linear movement would not be enough, the sensor would need to tilt side to side and up and down.
It is the addition of SR to compensate for X/Y axis camera rotation that I think would be the big step forward. Z axis movement compensation would be a minor addition.