By Joe Kashi, for the Redoubt Reporter
Image-stabilization hardware is probably the single most useful and important advance in photographic hardware in the past 30 years, but it’s not perfect, requiring careful use for consistently good results.
Although not a substitute for a fast-enough shutter speed, image-stabilization greatly extends our ability to work in many less-than-optimal situations, such as dim light or high-magnification telephoto shots. It’s important to differentiate among the various types of IS because some are stabilized in name only.
IS hardware only compensates for your body’s inherent minute tremors that cause noticeable image blur at too-slow shutter speeds and high-magnification telephoto shots. IS can’t compensate for blur caused by a subject’s inherent motion. Still, countering blur resulting from external camera shake is exceptionally useful.
So-called “electronic image stabilization” is something of a sham. It merely bumps up the ISO sensitivity and sets a faster shutter speed. It’s most common in older consumer digital cameras and usually results in noticeably higher image noise. Electronic IS is really just an auto-ISO feature and of no real value. You can just as easily set a higher ISO yourself, and more effectively.
“Optical” IS moves a few glass elements within a lens to compensate for shake. Optical IS was initially easier to implement and, when properly designed, can result in a two to four “EV” improvement. That’s very useful, particularly with telephoto lenses.
Until recently, optical IS was generally thought superior, but that’s no longer the case. There are a few significant disadvantages — each lens must be separately stabilized, which is expensive, and optically stabilized lenses tend to be a bit larger. Some optically stabilized derivative designs, such as Tamron’s 17- to 50-mm zoom lens for APS-C digital SLR cameras, seem less sharp than earlier unstabilized versions of the same lens. That’s likely due to the more complex optical path. However, if you shoot Canon, Nikon, Samsung, Panasonic or some Sony cameras, it’s either optical IS or nothing.
The third type of IS is “sensor-shift” in which the sensor itself makes minute movements that counteract any camera shake. Pentax, Olympus and some Sony cameras use sensor-shift IS. Until recently, sensor-shift stabilization was reputedly less effective than moving a few glass elements within each lens, but over the past few years, sensor-shift IS has substantially improved. Sensor-shift IS can stabilize any lens physically attached to the camera, a very useful capability as many excellent, compact, single-magnification “prime” lenses lack built-in IS hardware. With some older lenses, though, you may need to manually input the focal length to ensure correct stabilization.
Pentax’s sensor-shift IS can act as an anti-alias filter on demand, counteracting moiré false color interference patterns. Olympus’ five-axis, sensor-shift IS built into its flagship E-M1, E-M5 and E-P5 cameras seems able to provide a 4 EV to 5 EV stabilization that’s especially effective in stabilizing handheld video. As an example, when submitting automobile accident settlement packages to insurance companies, I like to include video taken from a vehicle driving at the posted speed through the collision site to show what each driver could see at what times. Such video tends to be very bouncy due to erratic vehicle and body motion, often to the point of unusability. After I started taking accident-scene videos with an Olympus E-P5 and its five-axis magnetically suspended IS system, my handheld accident scene videos became rock solid.
IS hardware is most effective at relatively slow shutter speeds where, after all, it’s most needed. Depending on the focal length of your lens, some IS hardware allows sharp, handheld images taken as slow as 1/3 second to 1/10 second. That’s far slower than you can reliably hold a camera without noticeable camera shake.
Because of their lower magnification, wide-angle and normal lenses can be handheld at slower shutter speeds before camera shake becomes apparent. Telephoto lenses, particularly high-magnification, long-focal-length lenses, require faster shutter speeds, even with IS engaged, but they still benefit from IS. You can expect a 2 EV to 4 EV advantage when using a telephoto lens with IS hardware, allowing significantly lower shutter speeds before blur becomes objectionable.
IS hardware is sometimes ineffective at intermediate shutter speeds in the range of 1/50 second to 1/200 second. That’s because the sudden stopping of a camera’s shutter and moving mirror often causes internal mechanical vibration that IS hardware may amplify rather than counteract, ruining images taken within this shutter-speed range.
Unlike the double images caused by external camera shake, the deterioration resulting from internal mechanical vibration is more subtle. It’s usually evident as an overall image softness, rather than the double images typical of externally induced camera shake. When that sort of generalized image softness occurs, it’s usually mistakenly attributed to poor optics, rather than subtle vibration.
I’ve had this problem occur, and more than once. To determine whether it may be a problem for you, test your camera with several lenses over a range of likely shutter speeds to see if, and under what circumstances, this might occur with your gear. Do not assume that your lenses are poor. Instead, first suspect internal vibration. Make your first series of tests using a sturdy tripod with the IS hardware turned off, and then a second set of identical images taken handheld.
Should internal vibration be a problem, you have several options. It’s best, of course, to use a faster shutter speed or a tripod if that’s feasible. Whenever using a tripod-mounted camera, turn the IS hardware off. Lens-based optical IS is usually toggled on or off by a manual switch built into each lens. Sensor-shift IS is usually turned on and off through a menu option.
If you prefer to use your gear handheld within a possibly problematic shutter-speed range, then determine whether your camera has an “anti-shock” setting. If it does, then try the shortest feasible delay setting. Anti-shock settings work by introducing a slight delay that allows internal vibration to subside before the photo is captured. Some cameras, such as the Panasonic GM series and Olympus cameras, include a “0” anti-shock setting that effectively negates internal vibration by acting like a nonmoving electronic shutter. Remember, though, that any anti-shock setting introduces some lag between the instant that you press the shutter release and the shutter’s actual release. That sort of delay is usually not a problem unless you’re photographing fast action.
Finally, there are the tried-and-true methods to reduce vibration. Hold the camera as steadily as possible, bracing your arms and upper body against something solid like a tree or building. Or, set the camera on a steady base, such as a table or a large rock, using the self-timer to release the shutter. Ideally, dampen camera vibration with a soft but heavy object laid across the top. Pros usually carry small sandbags for this purpose.
Hold your camera with both hands, one hand on the camera body itself and the other hand steadying the lens or opposite side of the camera. Eye-level viewfinders provide a welcome third point of body contact, further dampening internal vibration and external shake. If possible, avoid one-handed shots where you hold the camera away from your body with a single hand while framing in the rear LCD screen. That’s the shakiest technique of all.
Local attorney Joe Kashi received degrees from MIT and his law degree from Georgetown University. He has published many articles about computer technology, law practice and digital photography in national media since 1990. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.