Image stabilization is a technology built into cameras and lenses that reduces the blur caused by hand movement during exposure. It allows you to shoot at slower shutter speeds than would otherwise be possible while still getting sharp results. For handheld photography, especially in low light, image stabilization can be the difference between a keeper and a blurry reject.
How Image Stabilization Works
Image stabilization systems detect camera movement using gyroscopic sensors and then compensate by shifting either lens elements or the camera sensor in the opposite direction. This countermovement cancels out the shake, keeping the image steady on the sensor during the exposure. The system works in real time, making continuous adjustments as you shoot.
Modern systems typically provide between 3 and 7 stops of stabilization. A system rated at 5 stops means you can shoot at 1/8th of a second and get results comparable to shooting at 1/250th without stabilization. This is a dramatic improvement that opens up many shooting situations where a tripod would otherwise be required.
Lens-Based vs. Body-Based Stabilization
Lens-based stabilization (called IS, VR, OS, or VC depending on the manufacturer) places the stabilizing elements inside the lens. The advantage is that the stabilized image is visible through an optical viewfinder, making it easier to compose and track moving subjects. Each lens is optimized for its specific focal length and optical design.
Body-based stabilization (called IBIS, or In-Body Image Stabilization) moves the camera sensor itself. The major advantage is that every lens you mount benefits from stabilization, including vintage manual-focus lenses that have no electronics at all. Many modern mirrorless cameras combine both systems, using lens and body stabilization together for maximum effectiveness.
When Image Stabilization Helps Most
Image stabilization is most valuable when you are shooting handheld in situations where you cannot use a fast shutter speed. Low-light environments like dimly lit interiors, overcast days, and twilight scenes all benefit enormously. Telephoto lenses magnify camera shake along with the subject, so stabilization becomes increasingly important as focal length increases.
For video, stabilization is nearly essential. Even small hand movements that are invisible in a still photo become distracting wobble in video. Five-axis stabilization systems that correct for pitch, yaw, roll, and horizontal and vertical shift produce noticeably smoother handheld footage.
When to Turn It Off
On a sturdy tripod, image stabilization can sometimes introduce slight vibrations as the system hunts for movement that is not there. Many photographers turn stabilization off when using a tripod, though some newer systems detect tripod use and deactivate automatically.
When panning to track a moving subject, standard stabilization may fight against your intentional horizontal movement. Many lenses offer a dedicated panning mode that stabilizes only on the vertical axis, allowing smooth horizontal tracking while reducing vertical shake.
Stabilization and the Exposure Triangle
Image stabilization gives you more flexibility within the exposure triangle. Instead of raising your ISO to get a faster shutter speed in dim conditions, you can keep the ISO low and rely on stabilization to handle the slower speed. This preserves image quality by reducing noise. It also means you can stop down your aperture for greater depth of field without sacrificing sharpness to camera shake.
Remember that stabilization only corrects for camera movement, not subject movement. A fast-moving child or athlete will still appear blurred at slow shutter speeds regardless of how effective your stabilization system is. For moving subjects, a sufficiently fast shutter speed remains the only solution.