Photoclubalpha

Well, there's a menu item that's supposed to be activated when you intend to clean the sensor, just like it is there in the menu of any other Sony DSLR.

Well, that's OK.
BUT!
We seemingly do not need that menu item at all. We do not need a well charged battery that the 'sensor cleaning' requires. The sensor is quite open, and the mirror can well be lifted even with no battery inside the body. Just switch the cam off, lift the mirror, and do the cleaning. No matter if the battery is in or out.

Now why the 'sensor cleaning mode' is there at all, then?

My guess could be that some AF recalibration may be happening after the cam is reactivated after the 'cleaning mode'.
If I were the camera designer, I would put some recalibration light source around the AF module so that the slightly errant mirror position could not ruin the AF precision. So that activating the 'sensor cleaning' in the menu would start the AF mirror position recalibration after the camera is restarted.

Should be cheap and totally effective. But is it there or not, I do not know...

I never thought of that. Interesting.

Check the vibration when activating and turning off this mode. It is supposed to give the sensor a very powerful burst of dust removal vibration.

David

Yes, David, that vibration is startlingly strong, and the manual strongly implies that the vibration at 'sensor cleaning' must be enough to remove dust in most cases.

And I don't really think they do any automatic AF recalibration. I just think that such recalibration procedure could be implemented very easily and by very inexpensive means. And it would be very much worthwhile to have the means to compensate the aging and thermal/mechanical instability of those flimsy plastic parts.

agorabasta wrote

And it would be very much worthwhile to have the means to compensate the aging and thermal/mechanical instability of those flimsy plastic parts.

I have no doubt that the A55 is a capable camera but the more I read about "flimsy plactic parts" in this camera and the question of long term stability of the mirror, the more I think that buying the A580 was a good idea. Time will show if the A55 can stand up to rough handling and taking tens of thousands of images without causing problems.