Sunday, October 2, 2011

Lens Basics: Image Stabilization

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Canon EF 17-85mm IS Lens
Image stabilization is a wonderful technology that has recently been applied to a wide variety of lenses to help you get sharper images while hand-holding your camera. Canon calls this technology image stabilization (IS) and Nikon calls it vibration reduction (VR), but they both accomplish the same purpose.  They counteract the movements that occur when hand-holding your camera in order to stabilize the image and make it more sharp. Although results will vary by lens, IS/VR can generally give you sharp images at shutter speeds two stops slower than you could get hand-holding your camera.

Now let me explain that what that means.  As a general rule of thumb most people hand-holding their camera (without IS) can get a high percentage of sharp pictures when shooting at a shutter speed equal to or faster than the inverse of the focal length of your lens.  In simpler terms, if you are shooting with a 100mm lens, you want a shutter speed of 1/100sec to get a high percentage of sharp images.  The longer the focal length of your lens, the faster you need your shutter speed to be in order to get sharp images.  With a 28mm lens, you want your shutter speed to be 1/30sec; with a 300mm lens, you want 1/300sec.  With practice and good technique many photographers can get sharp images at shutter speeds slower than this rule of thumb, but for our purposes here, but stick with the rule. At any rate, the faster your shutter speed, the higher percentage of sharp images you will be able to take.

Here's where image stabilization comes in handy.  If your lens has image stabilization, you can shoot around 2 stops slower.  So with your 200mm lens, you can shoot at 1/50sec and still get a high percentage of sharp images.  With a 60mm lens, you can use shutter speeds of 1/15 sec, and so on.  This is extremely helpful when you are hand-holding your camera at in lower light conditions and at longer focal lengths.

Here's a few things to keep in mind though:
  1. IS/VR does not replace a tripod.  When you have very slow shutter speeds, IS/VR will be unable to give you sharp images, but a tripod won't fail you.
  2. IS/VR is not effective when your lens is on a tripod.  Make sure to turn it off.  A few lenses automatically sense when your camera is on a tripod--you can check your lens manual if you think your lens might be one of them.  But with lenses that do not automatically detect this, your IS can actually create blur when mounted to a tripod.  Be sure to turn it off. 
  3. IS/VR can not help you with the movement of your subject.  If you want to stop the motion of your subject so that it appears sharp, you need a fast shutter speed, or you can try panning the camera with your subject movement to keep it sharp. 

3 comments:

  1. Just a quick comment about point #2. There are now many lenses (especially in Canon's line-up) that can sense when a tripod is being used, and effectively switch off automatically. The EF 70-200 F/2.8L IS and the EF 70-200 F/4L IS are in that category.

    People should be sure to read the instructions that come with the lens (or camera, if they're using Sony/Minolta or Pentax cameras with internal image stabilization) to see whether or not the feature should be disabled when on a tripod.

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  2. Which you said. Nevermind. I'll wake up and open my eyes now...

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  3. Well, it's worth stating again, anyway. :-) I'm told that Canon's newest lenses will even reduce vibrations caused by the mirror when taking a picture. With these newer lenses (I think the 70-200mm f/2.8L II is one of them), it's still better to have IS on when on a tripod. Others are:

    EF 300 mm f/2.8 USM L IS
    EF 400 mm f/2.8 USM L IS
    EF 400 mm f/4 USM DO IS
    EF 500 mm f/4 USM L IS
    EF 600 mm f/4 USM L IS

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