IS and VR are brand terminology for the technology that Canon and Nikon (and other camera manufacturers) use in cameras and lenses to reduce blur. These acronyms stand for “Image Stabliziation” and “Vibration Reduction”.

At slower shutter speeds, camera movement introduces blur to the photograph. This movement is usually the result of the photographer’s hand or body moving slightly as they shoot a frame hand-held. If a tripod or other apparatus is not used to stabilize the camera during a long exposure, it easily picks up on the slightest movement which directly translates to a lack of sharpness.

Image stabilization technology’s goal is to enable photographers to hand-hold their cameras at slower shutter speeds than what has normally been possible while stilling getting acceptably sharp photos. Modern IS/VR usually has a 3-4 stop advantage, meaning a shot that would have otherwise required a 1/200 sec. shutter speed is now possible between 1/25 – 1/50 sec.

The photos shown here clearly demonstrate the effects of IS/VR. They were both shot at the same shutter speed of 1/6 sec with the lens at 105mm. IS was turned off for the image on the left, then enabled for the image on the right. The difference in sharpness is extreme.

The image stabilization technology found in consumer cameras falls into two main categories: optical image stabilization and digital image stabilization.

Optical Image Stabilization

Optical I.S. moves elements inside the camera/lens to counteract the movements introduced by the photographer. This IS is implemented in either the lens or the camera body.

In lens-based image stabilization, the lens has an element inside that is capable of moving. The lens detects the camera’s movement and responds by moving around the lens element to stabilize the projection of the image.

In-camera image stabilization is implemented in the form of a sensor that moves. Again, the camera detects the movements being introduced by the photographer, and moves the sensor around in response to stabilize the image.

In-camera image stabilization is used my some manufacturers because it enables I.S. on every lens in their lineup. Canon and Nikon do not put IS/VR into their camera bodies, only their lenses. This means that only certain lenses can take advantage of the technology and the feature usually corresponds to a higher price tag. An advantage, though, is that a new camera body is not required in order to take advantage of advances in IS technology.

Digital Image Stabilization

Digital image stabilization operates on the image after it has been captured. There are two kinds of digital image stabilization: one which crops and rotates the image, and other which drops exposure time and boosts exposure.

The first type of digital image stabilization slightly crops the image so that it can then be rotated around in response to the movement, stabilizing the image. You can think of this like a digital implementation of the techniques used in optical image stabilization, except it takes place after the image has been captured and shifts around pixels instead of light.

The second type of digital image stabilization plays with exposure. The camera will use a shorter exposure time in order to eliminate the blur, but this will also cause the resulting photo to be underexposed. The camera will then correct the exposure by brightening up the photo artificially. An unfortunate side effect of this method is that it increases digital noise, especially in shadow areas. You will see this for yourself if you try to push the exposure too far on one of your own photos in post production — after a certain amount, the noise and grain in the photo becomes noticeable.

IS Modes

Many cameras and lenses implement two different modes of optical image stabilization. The first mode will correct for both horizontal and vertical movements of the camera, while the second mode will only sense and correct for vertical movements. This is useful when you want to use IS while “panning” — purposely dragging the shutter while following the subject across the scene to create motion blur.

Thoughts on IS

While IS corrects for movement introduced by the photographer, it cannot counteract blur from a moving subject. The only way to freeze a moving subject is to use a fast shutter speed.

Image Stabilization / Vibration Reduction is a popular feature because while it adds a little extra cost to the equipment, it also enables many photographers to leave the tripod at home. With IS you can obtain sharp photos at shutter speeds that were not previously possible without anchoring the camera to a tripod or stationary object.

At the moment, IS is not usually found in lenses with very wide max apertures. For example, many Canon’s lineup of f/4 aperture zoom lenses have IS. A lot of f/3.5-5.6 kit lenses have IS. The technology is not, however, found in many f/2.8 zooms or fast prime lenses. You probably won’t find too many people complaining about this though*, since many photographers (legitimately) feel that IS is not a substitute for wide maximum apertures.

* Except those involved in the enteral rumor around Canon’s mythical EF 24-105 f/2.8 L IS, or perhaps the often rumored EF 24-70 f/2.8 IS.