Olympus PEN Mini / E-PM1 Review
Image StabilizationThe PEN Mini offers two distinctly different types of image stabilization. For still images, Olympus employs an optical image stabilization system that seeks to counteract camera shake by mechanically adjusting the position of the sensor itself. One obvious benefit of in-body stabilization is that the feature is available no matter what lens you put on the camera. The stabilization used for video capture is much different, however. The digital image stabilization employed in movie mode attempts to correct for camera shake, by comparing image elements after the fact and skewing edges to make them align properly. These two methods can produce strikingly different results.
Sensor shift stabilization
The E-PM1 offers three different flavors of mechanical (sensor-shift) image stabilization. With IS mode 1 active, the camera seeks to correct for camera shake in both horizontal and vertical directions. When you activate IS mode 2, the camera employs only vertical stabilization. This mode is designed for situations where you are panning the camera, following a subject that is moving horizontally across the frame. In IS mode 3, only horizontal stabilization is active, which is ideal for panning the camera horizontally while holding the camera in a portrait orientation.
The real-world effectiveness of any image stabilization system varies depending upon the photographer and their technique. In our daily use of the E-PM1 with image stabilization disabled, we found, as one would expect, that staying above a 1/effective focal length shutter speed prevents camera shake from having an appreciably detrimental effect on image sharpness. Because Micro Four Thirds sensors have a 2x 'focal length multiplier', this means that shooting with the kit zoom set to 25mm requires shutter speeds of 1/50 or faster.
With image stabilization enabled, our experience shows the E-PM1 capable of delivering up to three additional stops of acceptable image sharpness. In other words, with IS mode 1 active, we found we could reasonably expect to use a shutter speed three stops slower than the 1/effective focal length minimum and retain acceptable image sharpness.
When in-body image stabilization is activated the E-PM1's sensor is allowed to physically shift to counteract movements caused by camera shake. While this is generally effective, as we've noted in the examples above, there are some considerations to be aware of when shooting on a tripod. Should you neglect to disable IS when shooting on a tripod, we've found that vibrations from the shutter mechanism can cause the sensor to shift inadvertently, causing a blurry image.
|ISO 200, f/6.3 @ 1/100s
IS on (mode 1)
|In this 100% crop, vibration created by the shutter mechanism has caused to the sensor to shift, resulting in a slightly blurry image when viewed critically.|
When activating digital IS for video recording, the camera automatically attempts to correct for both horizontal and vertical instability, regardless of which IS mode is currently selected. In the samples below we take a look at two scenes, each captured with IS turned on and off. The following video samples are taken from the E-PL3.
In this video sample, the subject was shot handheld at a close range with IS disabled. The lens was set to a 36mm equivalent focal length. Camera shake is obvious throughout the clip.
|1280 x 720 Motion JPEG, .AVI file, 11 sec. 40.03 MB Click here to download original .AVI file|
From roughly the same shooting distance, IS is enabled for the video sample below. While camera shake is noticeably minimized, a close look at the edges of the scooter show perspective skewing as the digital image stabilization systems attempts to keep the subject in a consistent location within the frame. The result is distinctly unnatural in appearance, at time making the scooter seem as if it has been 'lifted' from the background.
|1280 x 720 Motion JPEG, .AVI file, 11 sec. 39.99 MB Click here to download original .AVI file|
This handheld video sample of a distant subject using a lens set at a 112mm equivalent focal length was shot looking down on the scene from a rooftop. IS is disabled. Camera shake is obvious throughout the clip, exacerbated both by the camera position (chest height with arms extended) and slight wind.
|1280 x 720 Motion JPEG, .AVI file, 11 sec. 43.25 MB Click here to download original .AVI file|
This video was shot from the same perspective as the sample above, but with IS enabled. We can see the digital IS system produces a 'jittery' effect in which perspective is shifted abruptly among prominent elements of the scene. While digital IS does reduce analog camera shake, the overall result appears neither natural or pleasing.
|1280 x 720 Motion JPEG, .AVI file, 11 sec. 43.81 MB Click here to download original .AVI file|
While the optical sensor-shift stabilization available in still images shows clear and obvious benefits to users (primarily the ability to shoot handheld at lower ISO settings), the benefits of Olympus' video stabilization system are much less clear. Using IS in movie mode does reduce camera shake, but introduces digital effects that some may find nearly as objectionable.
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