"Mic Drop Off"

[molecular]

I was reminded of this by the recent Tonor mic post in User Reviews, which reports a "mic drop off" of around 4 feet away - or something.

I would have replied there, but this seems more general - it also seems connected to perennial discussions of dynamics picking up less "room" and condensors being unsuitable on stage because they are more sensitive to distant sounds and so on.

The idea seems to be that certain mics are more sensitive within a certain boundary, and there is a sudden - well, drop-off - beyond that.

But a mic has no way of telling how far away you are, and provided you are not changing your position in the polar pattern, the increase in level will just be your increase in volume on account of being closer.

It's not possible for a mic and pre to apply more gain to something 1 ft away than it does to something 4ft away.

So what's the source of this "phenomenon"? Is there anything else going on that might in some circumstances generate a kind of "drop off" distance that is unique to a particular mic?