You may hear the terms image stabilization or vibration reduction when checking out digital cameras. They are essentially the same thing, except some camera manufacturers use different terminology. Nikon uses the term vibration reduction, and Canon uses image stabilization. Other manufacturers also include IS in their better models, but Canon and Nikon are the most popular brands.
The benefit of have cameras with image stabilization or vibration reduction is that you can avoid taking blurry pictures when the feature is turned on. It is meant to counteract the fact that it is difficult to hold a camera steady enough when the shutter speed is too slow.
Normally, one can hold a camera steady when there is enough light to allow the shutter speed to be fast enough. However, when there is not enough light, the shutter speed slows down, and it is more difficult to hold that camera still long enough to get a good sharp picture.
Camera makers have added the technology that basically allows the photographer to hold the camera steady at slower shutter speeds and not have to resort to using a tripod. It works best when photographing subjects that are not moving. When the subject is on the move, and the photographer is panning to keep the subject in the center of the frame, all bets are off. That is not what IS or VR is made for.
Keep in mind that not all forms of image stabilization are created equal. You may encounter an alternative term know as "anti-shake" technology. If the model you are considering uses that terminology, be sure to find out how that is being accomplished. Some cameras have software that does not have real image stabilization technology. Instead, the camera will boost the ISO setting to allow for a faster shutter speed, and because of the faster shutter speed, there will be less camera movement. However, boosting the ISO is not as good as real IS technology. Higher ISO settings lead to noisier images.
Exactly what can be accomplished with image stabilization or vibration reduction differs from one model to another and from one photographer to another. After all, not every person has the same abilities to remain steady while taking a photo. But, in general, manufacturers claim that their technology will help keep the camera steady for an additional 3 to 4 stops, where a “stop” is an increment of aperture measurement.
Here is a simple scenario. You can hold a camera steady without image stabilization when the focal length is set 100mm and the shutter speed is 1/100th of a second. With shutter speeds less than 1/100th seconds, the results will be blurry. Add image stabilization and you can hold the camera steady enough even when the shutter speed drops to 1/25 second. But keep in mind that with a human behind the camera, results will vary.
As the focal length increases, the tendency for camera shake also increases. It is much easier to hold a camera steady when the focal length is 28mm than it is at 280mm. Therefore, if you are shooting with long focal lengths, use a tripod or engage your image stabilization setting.
Even when your camera is mounted on a tripod, image stabilization can be a benefit due to the way some photographers press the shutter button. You really should do some experimenting with your camera’s IS setting to see how it will act, both when hand-holding and when using a tripod.