Lenses For SLR and DSLR Cameras - Optical Image Stabilization

Optical Image Stabilization

Image stabilization is a technique used to reduce image blur caused by the camera not being held steady. There are two kinds of image stabilization used in SLR and DSLR cameras and their lenses:

• In-body image stabilization is implemented by moving the image sensor in an attempt to counteract the sensed motion of the camera. The advantage of this technique is that it works for all lenses mounted on the camera, at least if the camera electronics are aware of the lens' focal length. This is most commonly done automatically, but some cameras (such as all Olympus bodies with IS) allow the user to input the focal length manually for use with lenses with no electronic coupling. In-body image stabilization is used in modern Olympus, Sony, and Pentax cameras.
• In-lens image stabilization is implemented in the lens itself, and moves the lens elements in an attempt to counteract the sensed motion of the camera. The inherent advantage of this kind of image stabilization is that it steadies the viewfinder image, allowing for more accurate framing and autofocus. The disadvantage is that you have to pay the extra cost for every lens you buy for which you want image stabilization. Panasonic, Canon, and Nikon use lens-based image stabilization. Some third-party lenses from Sigma and Tamron also have lens-based IS systems.

The effectiveness of image stabilization systems varies somewhat from implementation to implementation, but there seems to be no inherent superiority to either lens-based or sensor-based systems as far as the actual improvement in captured images.

Image stabilization systems can degrade image quality if the photographer is intentionally panning (as the system tries to negate the panning motion), or if the camera is mounted on a very sturdy tripod (the system drifts around slowly due to spurious measurements over the course of a long exposure). Some more recent IS systems can automatically detect these situations and disable the IS along the panning axis, or disable it completely if the camera is on a tripod.

Mounting a lens with optical image stabilization on a camera with in-body image stabilization does not provide improved results, since the combined effect of both systems will "overcorrect". Users of image-stabilized lenses on bodies with sensor-shift IS should determine which system offers superior performance and turn the other off.