When shopping for lenses for your digital SLR, you might have noticed that image stabilization goes by a few different names, most commonly either IS (among Canon lenses) or VR (for Nikon). But the lenses all tend to work the same way: Motion sensors in the lens generate feedback that directs optical elements to compensate for small movements, like the sort that occur when you hold a camera.

Of course, some cameras have image stabilization built into the body instead of the lens. If you have such a camera, the basic idea is the same. The key difference is that the motion sensors direct the camera's sensor rather than optics in the lens. The advantage is that you need to buy the expensive stabilization hardware only once, instead of in each and every lens.

Sounds great, right? You might be tempted to leave something like that on all the time. In reality, these motion sensors are a little too sensitive for 24/7 operation. If you mount a camera with image stabilization on a tripod or secure it to some other form of stable support, then you should generally flick the switch to off. (There should be a switch for image stabilization somewhere on the IS or VR lens, or, if it's built into the camera, somewhere on the body.)