Image stabilization systems are all meant to do one thing: reduce the effects of camera shake to prevent you from getting blurry images. If you know that, and know their limitations, you’ll find them very useful; if not, you’ll wonder why you can’t get a sharp picture of a racing car even though you’ve got an IS lens.
Rule 1: Stabilization systems are not a replacement for proper technique or support.
If you have good hand-holding technique or a tripod, you can always get a sharp image at shutter speeds below the 1/focal length threshold. No issue. If you don’t, then a stabilizer will help a bit, but it can’t prevent your finger from jerking when you press the button – that’s training. You can’t use a stabilizer for a long exposure, either. There’ll still be camera motion because it’s physically impossible for a person to stand that still. Lean the camera against something or get a tripod. It will help you when you’re shooting from an unstable platform – such as a boat or moving vehicle – but make sure you disable the lens’ panning mode to prevent it from canceling out motion in one direction only, believing it to be panning rather than irregular camera movement.
Rule 2: Stabilization systems will not affect subject motion.
The stabilizer is in the lens, or on the sensor. Either way, it’s attached to your camera. Not the subject. But you’d be surprised how many people think that VR or IS or OSS or SSS or whatever will also keep the bird still for you to get the shot. It won’t. Your subject is still bound by the same minimum shutter speed rules as all other subjects: about 1/30s-1/60s for people, 1/500s for human action sports, 1/1000s for motorsport, and somewhere between the two for animals.
Rule 3: Stabilization systems have an optimal window of shutter speeds.
Generally, if the manufacturer claims an X number of stops improvement, then deduct one and use that as a rule of thumb. So if a lens offers four stops, then your lowest shutter speed is going to be 1/focal length x (1/2)^(X-1). Confused? Example: 100mm lens with 4-stop stabilizer. Don’t expect sharp shots any slower than 1/100s x (1/2)^(4-1) – that’s somewhere between 1/10s and 1/15s.
What they don’t tell you is that there’s an upper limit to stabilizer effectiveness, too. Above a certain shutter speed, the stabilizer mechanism can’t respond fast enough – so you’re actually going to get a bit of smearing or double imaging. In general, I’d turn it off above 1/500s or so.
Rule 4: Not all stabilizers are created equal.
There are three types of stabilization: lens-based, which has a moving element controlled by two or more gyroscopes; sensor-based, which moves the sensor through lateral translation axes, and in the newest generation of cameras, also yaw, pitch and roll axes; and finally, electronic systems that use software-based image subtraction and have no moving parts at all. The least effective are electronic stabilizers – they are effectively useless, and worse still, leave behind odd image artifacts. Lens-based stabilizers are generally more effective than sensor-based stabilizers. This is because the moving lens element is generally at the nodal point of the lens, and only has to tilt in the opposite direction to compensate for relative camera motion; it can compensate for a greater degree of camera shake than a sensor based system, because the sensor has to move through the actual distance the image is displaced by on the focal plane; this means that sensor-shift systems get less and less effective as the focal length increases.
Rule 5: Turn off the stabilizer when using a tripod.
Stabilizers, by definition, use moving parts. The problem here is that when everything is locked down and not moving – i.e. a tripod-based scenario – the moving parts can’t stay perfectly still, unless they’re locked in place – i.e. the stabilizer is turned off. Even the systems which are claimed to be able to detect tripod mode don’t physically lock down unless turned off manually.
Rule 6: Stabilizers always cause some sort of image degradation.
This is unavoidable; to deliver optimal results, the optical formula must be precisely matched by the physical configuration of the lenses. Fine manufacturing tolerances and errors are enough to cause subpar performance; imagine what a moving element does to that mix. Conclusion: turn it off, lock it down, and use a tripod if utmost image quality is your objective.
Beware of the limitations, but also know that stabilization systems can give you a little edge when it comes to unique images – the best example I can think of is when you want static buildings but a little motion blur in the people to convey a sense of activity; throw in a longer focal length and it’s not really something you can produce without a tripod (often inconvenient, or downright disallowed). Another example is where you’re shooting wildlife with a monopod at dawn or dusk; light is marginal and you’re not using a tripod for maximum flexibility, but you need a little more latitude with shutter speed to keep the quality up. It’s situations like this where stabilizers shine. MT