When to switch IS off
Save battery power and get sharper results in certain situations
While image stabilization can take the edge off vibrations caused by camera movement, it has no effect on subject movement. If the shutter speed is too slow to freeze a moving object, you’ll still end up with a blurred shot. The problem can be further exacerbated by the relatively small maximum apertures that IS lenses often have: you may have no option but to increase the ISO sensitivity when shooting action, just to get a usable shutter speed.
There are other things to bear in mind when shooting with IS. For a start, not all IS lenses are compatible with tripod work. Some of Canon’s lenses can detect when the camera is on a tripod and will stop working, but others will not. Regardless, it’s usually better to turn off IS when shooting from a sturdy tripod in calm conditions, as otherwise micro-adjustments from the IS system can actually introduce blur. This is particularly relevant if you’re using Bulb mode to shoot any longer exposures.
Switching off IS when you don’t need it can allow you to shoot for longer, too. Image stabilization draws its power from the camera battery, and every time you half-press the shutter release button, the IS system kicks in – whether it’s to physically stabilize the image (with Mode 1 or Mode 2 settings), or to calculate the stabilization that is required (during Mode 3).
Avoid removing an IS lens when the Image Stabilizer is active, as this can cause a malfunction.
The Stabilizer continues operating for a couple of seconds even after you’ve taken your finger off the shutter release button, so it pays to wait until you’ve heard (and felt) the ‘thunk’ of the IS lens grip locking into position.