Originally posted by falconeye You have an incorrect idea about the algorithm behind the SR system. This isn't probably the thread to dig into this too deep.
In summary, imagine that the SR system observes rotation about two body axes and does a frequency analysis of them. Then, for each frequency, it detects its phase and amplitude, subtracts the latency of the SR mechanism from the phase, and retransforms the result into real space. It then multiplies the result by focal length and steers the magnets accordingly.
If you are lost by now (the anticipated effect of my explainations
), then you may just want to remember this:
It
does anticipate movements. And there are no brakes
That's a great explanation of echo cancellation in a telecommunications system or perhaps of a digital frequency filter. But .....
In my hands, at any rate, the tremor
is quite irregular and therefore not necessarily predictable on a millisecond basis. My hands go back and forth but not evenly like a pendulum.
The way I understood it, MEMS (micro electro-mechanical systems) emulating gyroscopes measure and counter movement in an interval that is small compared to the open-shutter interval. Pentax may still be using the Invensense IDG-300 for this purpose.
In a camera, the system is not looking for a vibration (as we see it) but individual movements in this direction or that. Each movement is countered without waiting for enough periods of movement to determine a vibratory state. Given the randomness of shaky hands, the sensor may wait forever for variation showing a consistent frequency and amplitude.
If the period of the movement were large enough, a system could detect that gross movement (panning) and turn off or modify SR in one direction (at least) while continuing to correct for very small
random movements.
While all that sounds very profound, I'm actually a lousy photographer who emerged from university unscathed by electrical engineering. But I do read a bit and have an analytical streak that I feed with these discussions.
That also means I'm glad to be corrected where necessary
Cheers!