One of the great advantages of an SLR camera is the ability to attach long focal length lenses and capture high magnification images of faraway objects. One of greatest challenges, then, is holding said lenses steady during image capture. You may think you have a steady hand, but as you have read here, you are probably wrong. Luckily, lens manufacturers have solved the hand holding problem by incorporating image stabilization features into the lenses. Tradition has it that one should be able to capture a sharp image by hand holding the camera and setting the shutter speed to 1/focal length. Chances are, you can do much better than that. The reason is that little button on the side of your lens that says IS (or VR for Nikonians). Image stabilization routinely enables sharp hand held photos at shutter speeds that are 3-4 stops slower than the 1/focal length rule would imply. There is no doubt about the benefits of image stabilization but how does this magical technology work?
The secret to an image stabilized lens is an internal lens element that is allowed to float off of the original optical axis. While the front and rear elements remain stationary, the internal floating lens bounces to and fro to compensate for the movements of our shaking hand. The scenario roughly unfolds as follows. Tiny gyroscopes and accelerometers detect subtle movements of the lens. They then trigger circuits which move the floating lens in equal and opposite directions to counteract the movement.
This magic is normally hidden from our prying eyes, but we’ve managed to dissect an example to show you how this works. The video below shows a Canon 18-55 kit lens with its front element removed. Once inside, you can clearly see the floating lens element dancing around in its desperate attempt to stabilize the image presented to the camera sensor. Remove one more layer from the lens and you can marvel at the complexity of the movements involved in the image stabilization process.
So is image stabilization worth all the fuss? Definitely. The top two images below show hand held photos taken at shutter speeds comparable to 1/focal length (in this case 300mm). As shown, sharp images can be captured with image stabilization on or off. However, as we slow the shutter speed three stops, the image stabilized capture still retains good sharpness while the non-IS image is a total loss.
Image stabilized lenses have made their way to us in several iterations of technology. Because of that, there are several situations which require different treatments of the IS or VR setting.
- Camera mounted on tripod – Enabling the IS/VR setting essentially unlocks the internal lens element into its “floating” position. When a camera is stationary on a tripod, the unlocking of the floating lens can actually degrade images by bouncing around unnecessarily. Later generation “smart” IS systems can overcome this weakness so check your manual for the best advice.
- Panning the camera – Early IS/VR lenses had trouble differentiating between accidental camera shake and the intentional camera movement that comes from panning. Different generations of technology handle this differently. You may need to enable a switch to alert the lens that you are panning or the lens may handle this on its own. Check your manual for the best advice.
So now that you know how the technology works, make sure to take advantage of it. We live in a glorious age when the blurriness of our photos is not dependent on the last cup of coffee we had. Just aim your camera and fire away.
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