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Tuesday, May 24, 2011

The Promise Of Stabilization

Between image-stabilized lenses, in-camera stabilization and high-ISO technology, the game has changed for photographers seeking the freedom to shoot handheld

This Article Features Photo Zoom

The Canon EF 70-200mm ƒ/2.8L IS USM, Sigma 70-300mm ƒ/4-5.6 DG OS and Tamron 18-270mm ƒ/3.5-6.3 Di II VC lenses feature in-lens stabilization.
Other significant differences between both IS technologies affect the way you shoot and the price you pay for lenses. Cameras with sensor-shift IS generally work well with any compatible lens, including older ones. IS lenses tend to cost a bit more than their non-IS counterparts, so you have to factor that into the equation. However, only image-stabilized lenses can be set to show the stabilization effect through the camera's optical viewfinder. A few sensor-shift bodies let you preview the IS effect in Live View mode via the large LCD or through an electronic viewfinder (when it's available). Some shooters find using a live IS preview in either system to be advantageous, while others note how fast it drains the camera battery.

The best IS lenses also feature special panning modes or switches for use when you're tracking a moving target. These produce superior results by ignoring side-to-side motion and only reducing shake along the vertical axis. Other lenses can detect when the camera is set on a tripod automatically and turn off the IS so you can save battery life. Finally, when it comes to shooting video, both IS systems can help reduce shake to some extent, but IS lenses are generally quieter and further away from the built-in camera microphone. At least one zoom lens from Panasonic has a completely silent IS engine.

High ISO Changes The Rules For Working Without A Tripod
You may have noticed that neither the light-gathering capacity of the lens (determined by its maximum aperture) or the ISO setting of the camera is factored into the Reciprocal Shutter Speed Rule. These two features are only indirectly related to the amount of blur you can expect when shooting at low shutter speeds and, instead, determine whether you need to use a low shutter speed at all to produce a proper exposure. A brighter lens and higher ISO settings both let you use a faster shutter speed in a given low-light situation. Unfortunately, large-aperture telephoto lenses are expensive and rarely give you more than a two-stop advantage over a cheaper lens. But that two-stop advantage (for example, ƒ/2.8 vs. ƒ/5.6) is worth the price if you're an avid low-light shooter or if you want the added depth-of-field separation provided by wider apertures.

Increasing the camera's ISO to improve low-light performance can give you several more stops of improvement compared to a brighter lens or image stabilization. Many point-and-shoots do this automatically when their "electronic" image-stabilization feature is turned on. However, the price you pay for increasing ISO is a decrease in image quality. How much it decreases depends on the camera and its sensor. Most DSLRs let you dial up ISO to gain a three- to five-stop improvement in light sensitivity (compared to the camera's base ISO) before image quality becomes unacceptable. For example, assuming you own a fairly modern APS-C DSLR with a base ISO of 100, you may find images shot at ISOs from 800 (three stops) to 3200 (five stops) to be acceptable.

Testing Your Minimum Handholding Speed

Because everyone is a little different, it makes sense to test your personal minimum handholding speed with each of your lenses. The process is simple. Find a subject with fine lines in it (a tree with open branch structure will do nicely), set the camera to Shutter priority, and then take a series of photographs at progressively slower shutter speeds. We recommend starting at a shutter speed of at least 1/1000 sec. and finishing at ¼ sec. Open all of the photos on your computer and view zoomed in to actual pixels. You'll notice that there's no dramatic difference from one to another. Instead, there's a gradual softening as the shutter speed gets slower. At some point, the softness becomes objectionable and the shutter speed before that is your minimum handholding speed. Keep in mind that this is the minimum. It always makes sense to shoot at the fastest shutter speed you can when you're going handheld. It's a terrible feeling to get home after a day of shooting only to find that all of your images are soft.


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