neuroanatomist said:
Does IBIS stabilize instantly? Or, is it 'always on' (and how does that affect battery life)? How effective is IBIS with 300mm and longer lenses?
Its always on. Must cost some draw on battery. Since most pocket cameras has it I not sure its significant even if DSLR sensor is somewhat larger = somewhat more energy needed.
On DSLR effectiveness to my knowledge there is no agreed way of calculating this. Tests seem to vary widely.
The main advantage of course is that with IBIS all lenses are stabilised.
Recently IBIS also combines with in-lens stabilisation being on (have no info how this boosts the overall IS effect). After it has been shown you can have both I really hope Canon implements this.