Action sports photographer and Canon Ambassador Richard Walch shooting with the Canon RF 100-500mm F4.5-7.1L IS USM, one of the range of Canon lenses with built-in optical Image Stabilisation. Note the switch on the side for selecting between the three IS modes available.
Camera shake is the thief of sharpness. The tremble of your hand as you hold the camera, the slight jarring when you press the shutter release – even a tiny movement during the exposure can result in blurring in the image.
Much of the time, you won't notice the effects of camera shake. If you're shooting with a fast shutter speed or a wide-angle lens, the blurring may not be significant enough for you to register it – but it will still be there, and it might become noticeable if you make a dramatic crop or a large print of the image.
The obvious way to eliminate movement of the camera during the exposure is to fix it to something that will not move, such as a tripod, and to take precautions against jarring it, such as using a remote shutter release. However, a tripod is effective only if it is sturdy, which usually means heavy, so you can't always carry one with you. There are also many situations where a tripod is just not practical, and several where the use of a tripod is not permitted.
Fortunately, Canon offers another method of reducing, if not eliminating, the effects of camera shake: Image Stabilisation (IS).
There are various kinds of IS. Let's start with lens-based ("optical") IS.The first lens with Image Stabilisation was introduced in 1995. It approached the problem of camera shake laterally. Rather than trying to stop the camera moving, a stabilised lens introduces a compensating movement within it, with the aim of keeping the image static on the camera's sensor.