Posted on Nov 29, 2011 in Tech & internet
I know that when I push that little button on my camera all the pictures are less shaky looking, which is great — but I want to know more. How does the image stabilization in my camera actually… stabilize the image?
Image stabilization (IS) is a handy feature found on some higher end cameras and lenses for DSLR cameras. This marvel of modern technology lets you handhold cameras at unheard of shutter speeds and focal lengths while still getting a sharp, crisp picture with no noticeable camera shake. So how does this bit of magic work?
The primary form of image stabilization used is optical stabilization, meaning the recorded image is stabilized by altering the optical path to the image sensor. This is done in one of two ways.
In a lens based IS system, such as Canon’s or Nikon’s, there is a “floating” element inside the lens (lenses are in fact comprised of numerous pieces of glass inside the lens barrel) that is moved using electromagnets to compensate for the movement of the camera. Camera shake is detected by two gyroscopic sensors — one for horizontal movement and one for vertical movement. As such, this form of stabilization can compensate for up and down and side to side shake — but not a rotation of the camera. Despite this, it still performs incredibly well, allowing photos to be taken in very low light levels without the use of flash.
The downsides to lens based optical image stabilization include cost — if we’re talking a DSLR lens system, the IS is in each lens and must be absorbed every time an IS lens is purchased. IS also should be turned off when panning, as it can disrupt the sharpness of an image when following a moving object. Finally, it should also be disabled when on a tripod as it can cause erratic results.
Sony, Pentax, Fuji, Olympus, and others use a form of mechanical image stabilization where the image sensor itself is actually moved incrementally to reduce the effects of camera shake. Again, sensors are used to detect camera movement and the image sensor is moved slightly to correct for it. This type of stabilization is most commonly found in point and shoot cameras having IS, though Sony, Pentax, and Olympus all use it in their DSLR systems as well. One of the advantages of sensor shift IS is the ability to compensate for movement in a rotational direction — something lens based IS cannot do. It is also, in the long run, cheaper — your IS system is in the camera and does not have to be duplicated in every lens purchase.
On the downside, since the image is corrected at the sensor, the image in the viewfinder is not stabilized. Also, the image as seen by the autofocus system is not stabilized either, which can cause photos to still be slightly blurry — due to the AF being unable to function properly due to camera shake.
Finally, some video cameras use a form of digital image stabilization. In this case, the correction takes place in real-time as the image is shifted from frame to frame, using pixels outside the border of the visible image to provide a “buffer” for the motion. This reduces annoying vibration or shaking from the video, yet preserves video quality as the noise level does not increase.
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