Quote Originally Posted by Loupey
In-lens IS must always be activated before shooting. Even with the camera on, the shutter release button (or whatever camera switch you designate) must be pressed to activate the IS servos. These servos turn off after about 2 seconds after releasing the switch. It has to be this way - the servo mechanisms on the larger lenses draw a lot of power and imagine all the wear-and-tear if they were always on when one is walking through the woods.

I would think that in-camera IS works the same way for the same reasons. You just can't see it or feel it.
Hmm... with my FZ7K there are two MEGA O.I.S. modes, Mode 1 and Mode 2.

Mode 2 is activated as you describe, only when the shutter button is tapped. IS disengages right after you take the picture or when you release your finger off the shutter button.

Mode 1 is activated all the time, whether your finger is on the shutter-button or not. You get a stabilized image in the VF/LCD, so long as the camera is turned on and is in any shooting mode. (e.g. aperture-priority, program, manual, etc.). Yes, I have noted that my battery power goes down faster than usual, and in quiet conditions the IS noises are quite audible. And I would imagine that Mode 1 puts a lot of strain on the camera/lens.