When taking any photograph motion can be broken down into two groups. Camera motion and subject motion. Motion itself is not a bad thing. In fact there are many photographers who create some incredibly nice images accentuating motion using both subject and camera motion. But if we want an image really sharp a moving camera - or camera shake - can be an image killer.
With any movement, we can change the shutter speed to control the effects of motion. The faster the shutter speed, the sharper the image. You’ll also find that the effects of camera shake are less prevalent with a wide angle lens than with longer lenses.
There has been a rule of thumb that you could hand hold your camera if you shot at a shutter speed that was the reciprocal of the focal length of the lens you were using. For example, with a 200mm lens you would want a shutter speed of 1/200 second or faster if you were going to hand hold the camera. Of course, everyone is different and you need to test this for your own shooting style.
About 20 years ago the camera manufacturers started to roll out this new technology called Image Stabilization. (In the Canon world it’s called Image Stabilization; in the Nikon world it’s Vibration Reduction. We’re Canon shooters so for this article we’ll us IS but the concepts are the same.)
It was always thought that the only way to reduce or eliminate camera shake was to stop all camera motion. But with this technology they accepted the fact that this is often easier said than done. The IS technology instead introduces motion into the camera using a special IS lens group. Two gyro sensors - one sensitive to horizontal movement and one sensitive to vertical movement - detect the speed and angle of any camera movement. A microprocessor in the lens analyses the data and moves the IS lens group at a speed and direction to counteract the camera movement.
Today’s IS lenses can detect and correct for camera motion well enough to allow you to use shutter speed two to four stops slower that you might otherwise. But remember, this only corrects camera motion, not the motion of your subject.
Image Stabilization systems vary greatly, not just between manufacturers but also between individual lens models. With some lenses you can only select On or Off, while others offer various modes of operation. Read your user manual for your specific lens to understand what your IS system does.
In the Canon world, if you have two modes, you’ll find that in one mode the IS system will correct for motion both horizontally and vertically. (Vertical movement is called “pitch” while horizontal movement is called “yaw”) Another mode corrects only vertical movement. This is an important distinction when you want to pan your camera while shooting a moving subject like a runner, sports car or anything moving horizontally across the frame. Some of the newer lenses are now smart enough to detect whether the camera is being held horizontally or vertically and will automatically disable IS for the axis that’s parallel to the direction of the pan.
When to turn IS off
Image stabilization is a wonderful tool that can really improve the sharpness of your images but be careful. There is a time and place to use IS and a time to turn it off.
If you put your camera on a sturdy tripod, you’ll want to turn IS off. If not, the system will constantly try to correct for movement and can actually soften images. Ironically, even if the camera is rock solid and doesn’t move, the IS system may go into something called a feedback loop, in which the camera’s IS system essentially detects its own vibrations and starts moving around.
A final consideration for turning off Image Stabilization is to conserve battery life. The IS gyros do take a relatively large drain on the battery and if you are at risk of running out of battery power, turning off the IS will help.
Also, if you’re shooting in a studio environment where your strobes make up the majority of your lighting, you should turn IS off.
One final note:
Image stabilization is just one tool that is available to you as a photographer. With the right application it can deliver great results but it should be noted that if you want the sharpest results when photographing still subjects, nothing is better than a good camera mounted on a sturdy tripod with any Image Stabilization turned off.
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