There's no published data from any of the major lens manufacturers that I'm aware of. Canon certainly don't publish data on stabilization other than their "up to 2/3/4 stops" statements.
I presume they are tuned for a bandwidth in the cycle/sec to the 10s of cycles/sec range. I think the IS system on the FTM lenses might be tuned for some lower frequencies because they are said to help stabilize video when walking with the camera (presumably the source of low frequency movement)
They don't need to be tuned to high frequencies because people's hands don't shake at high frequencies! The plot here (http://www.bobatkins.com/photography/tutorials/mlu.html) shows camera mirror induced vibrations, which do have a higher frequency than what you'd expect from hand held movement. The major vibrations while the shutter is open seem to be at around 30Hz. However IS systems aren't really designed to minimize mirror induced vibrations (though they may work to do that in some cases).
IS systems certainly don't work at very low frequencies because the system drifts. At zero frequency (i.e. with the lens on a tripod), IS with exposures of maybe longer than 0.5s (that's just a guess) causes blur though drift of the IS system. At don't know at what point the drift becomes larger than the stabilization. Very low frequency stabilization could also be a problem when panning the lens, for lenses that don't have the option to switch off stabilization along the panning axis.
My guess would be that the bandwidth is maybe 1Hz to 50Hz at the outside. Probably more like 0.5Hz to 25Hz. I've read that hand tremor peaks in the 8-12 Hz range so I'd assume that's where IS systems are tuned for best performance.
I've seen some data on Canon's stabilization system for professional video shooting. There the stabilization seems to be tuned for maximum effect in the 2Hz to 10Hz range. Those systems use VAP-IS (variable-angle prism image-stabilization) which is a little different then the method used in EOS lenses, but the principles are the same, though they may tune the IS to include motion due to walking with the camera as well as hand/shoulder holding it.
If you want some technical reading on the subject, try this:
http://www.image-engineering.de/library/conference_papers/image_stabilizing.pdf
I suppose you could measure the characteristics of the lens you are interested in, but I don't know what the point would be. There's nothing you could do about it and the way to minimize image blur is to put the lens on the biggest heaviest tripod you can find and use a remote release with mirror lockup. It's not like you can control the frequency at which your hands shake when handholding the lens, or easily tune a tripod for resonance in a particular frequency range. Even if you could, I doubt it would be of any practical help and tuning for resonance would only increase the vibrational amplitude, something you certainly don't want.
|
