Originally posted by Steinback I generally leave it on unless I'm shooting with a manual zoom at more than one focal length or I'm using a tripod.
Ditto.
One thing to consider: In THE CAMERA, Ansel Adams speaks of shooting a 135 film SLR with a 50mm lens. He tested the ROT (rule of thumb) about picking a shutter speed that's 1/FL, which in the test case would be 1/50 or 1/60 second. He did not get sharp shots. He had to go to 1/250 for acceptable sharpness. That's a 2 f-stop difference.
With SR on my K20D, I expect a gain of about 2 f-stops. So many of us are tempted to exploit that gain;
OOOH, I CAN SHOOT THIS 100mm LENS AT 1/25 INSTEAD OF 1/100!! Wrong. If you want best sharpness, follow the 1/FL ROT. But if you're shooting humans in action, don't worry about it. Our human visual systems are very tolerant of less-than-crisp renditions of humanoid features. That's how we're wired.