Making Sense of Lenses: The In-Lens Image Stabilizer

The Problem of Camera Shake
When Camera Shake Is Most Likely to Happen
Canon's Image Stabilizer Technology
Why Put an Image Stabilizer in the Lens?

The Problem of Camera Shake
It happens all the time: You set your camera’s shutter speed to the fastest setting your lighting conditions will allow. You stand still and snap a picture. You eagerly examine the results—but there's just enough blur to turn a great shot into merely a good one. What causes this annoying blur? And how can you get rid of it?

The culprit is camera shake—the slight movement of your camera as you capture an image. It's often caused by the simple act of pressing the button to snap a picture, and it's nearly impossible to eliminate during handheld shooting. Sure, you could stabilize your camera by using a tripod, but that would limit your freedom to stroll around and snap pictures of whatever catches your eye, and whenever you catch it, too.

When Camera Shake Is Likely to Happen
Camera shake is typically at its worst when you’re shooting at slower shutter speeds (such as 1/100 and below) and at longer focal lengths (that is, when you're zoomed in close on a far-off subject). Here are some specific situations in which camera shake can especially detract from the quality of your pictures:

  • Telephoto shooting: Using a telephoto lens lets you get close to the action—whether it's a basketball game, a school play, or a graduation ceremony. But because of the long focal lengths involved, even slight camera movement can result in blurry images.
  • Evening/Night scenery: There’s nothing like a flash to ruin the nuances of an outdoor evening picture. To get enough light for nighttime shots, you must set your camera to a slow shutter speed. But if you leave the shutter open for too long, it will be nearly impossible not to move the camera even a little bit before the shutter closes.
  • Indoor environments: Indoor settings pose a similar challenge. Shooting without a flash lets you capture the nuances of your environment—and may be required at museums or special events—but using a slow shutter speed virtually guarantees blur.
  • Panning: As you move your camera horizontally to follow the motion of a running athlete, speeding car, or active child, even the slightest vertical bouncing can rob your image of clarity.

Canon's Image Stabilizer Technology
To compensate for the camera shake that's virtually inevitable during handheld shooting, Canon has designed its removable SLR lenses with a built-in Image Stabilizer (IS). Canon first introduced a lens with camera shake compensation in 1995. Since then, Canon's IS Lenses have continually increased their efficiency and accuracy in correcting shake.

Every Canon IS Lens contains a compact, lightweight image stabilizer unit. Built with sensors, actuators, and an optical correction system, this unit works with a high-speed microcomputer and two vibration gyros to enable highly reliable and accurate camera shake correction.

How do these lenses prevent blurred photos? They correct for camera shake by shifting certain optical components in inverse relation to the lens movement. This shifting helps ensure that incoming light rays will maintain the correct angle relative to the camera's optical axis as well as the correct position on the film or capturing element.

Why Put an Image Stabilizer in the Lens?
If camera shake is caused by movement of the camera body, why does Canon put the Image Stabilizer in the lens? The answer is two-fold: For greater correction accuracy; and to provide a more stable viewfinder image.

To ensure highly accurate correction, each Canon IS Lens features a customized optical correction system and controlling mechanism. This approach supports the unique optical design and specialized performance of each lens. It would be nearly impossible to deliver such precise camera shake correction by placing a "one-size-fits-all" image stabilizer within the camera body itself, because serious photographers frequently switch lenses for a variety of effects.

Having a stable viewfinder image is essential to good SLR photography. The image stabilizer built into Canon IS Lenses reduces image blur not only in photos but also in the viewfinder. This clear view enables photographers to make better shooting decisions with less eye fatigue.

A good viewfinder image makes photography easier in several key situations. With a clear view, you can more accurately frame shots to capture every detail. You can also focus on one part of your subject with the utmost precision, making it stand out to improve your overall composition. Panning becomes easier because the lens allows you to follow the subject while stabilizing any motion perpendicular to your intentional camera movement to keep your moving subject in plain view. And you capture more of those fleeting photo opportunities, because the clear viewfinder image helps you notice even the tiniest changes in your field of vision.