It's a hard trick to explain, but i will try. Keep in mind we don't know exactly how it's works sometimes, why sometimes it's possible and sometimes not. But we've done some progress on it.

We know the ghosts have differents "status" or "patterns" : moving pattern, (or do nothing), and attack pattern. A lot of ghosts in this game have a not RNG attitude : when we're too close from the ghosts, they attack you instantly (nearly all of the ghosts of this game). Of course they can decide to attack you without it too.

The point is : when you take a photo, the ghost is like "frozen" a couple of seconds. And when you take the photo in mid distance, if just after that, you move from the ghost, for having the pattern of attack, your camera is able to shot the ghosts instantly without waiting, during all the time the ghost is frozen. You can full charge 2 or 3 photos, or maybe spam and make until 5 photos maybe. Could be usefull if you're aim the head (+20 damage each photo).

It's an easy trick to do with the crawling girl and long arms. But particullary difficult to do with Ryozo, the Master, Yae, or the Assistant. It's seems they have different pattern of moving, and only some patterns can activate the glitch. It's only a supposition. And finally it's not possible to activate the glitch on Kirie, but it's seems to be working for all of the other ghosts.