In article , PeterN
wrote:

The important thing to remember when it comes to IS/OS/VR is that it is
there
to provide a fix for camera shake, not subject movement, and once you have a
shutter speed over 1/500 sec IS/OS/VR is irrelevant as the high shutter
speed
should freeze all subject movement. Since you shot those ducks at 1/2000 you
could probably have managed without IS.

I usually turn off IR for any critter tracking,

be sure to leave uv on.

as it slows down the
tracking a tad.

actually it doesn't, since stabilization is an independent system which
keeps the subject steady in the frame, making it *easier* for focus
tracking to work.

The shutter speed stability depends on the user's
individual hand stability, speed of the critter, and the focal length of
the lens.

the shutter speed stability depends on the shutter mechanism.