iMovie '09: image stabilization results in distorted movies

iMovie '09 comes with a useful image stabilization feature in which the program will analyze video content for shakes and jitters, and then apply a routine in which it zooms in slightly on the original file and pans around to compensate for the jitters, smoothing them out. While this works well for the most part, there are some situations in which it may cause additional problems.

Apple Discussions poster Kevin Berube writes:

"The more you stabilize a video the more it appears to be somewhat warbly (for lack of a better term). It almost looks like lens distortion but obviously not. Its bad enough to be very noticeable and headache inducing."

The stabilization algorithm requires that videos have full and complete pictures for every frame in the video. If a series of frames has incomplete or warped images in each frame, the stabilization function will result in a slightly warped final product since it will try to align parts of frames that were exposed at different times.

In some instances, this may be unavoidable, because certain camcorder types (largely those with "CMOS" image sensors) use a "rolling shutter". This kind of shutter will scan an image through a frame from one side to another, instead of snapping the whole frame at once. For these camcorders, depending on the amount of movement and the shutter speed, users will see various degrees of distortion in the movie after applying stabilization.

Until Apple releases an updated stabilization algorithm to accommodate cameras with rolling shutters, it is recommended that users experiencing distortion not apply the stabilization feature. For users who have already applied the stabilization to clips, they cannot remove it from the clip without reimporting it. However, the stabilization can be disabled for the clips in a project by double-clicking the clip (or choosing "Clip Inspector" from the "Window" menu) and uncheck "Smooth clip motion" next to "Stabilization".

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