I.v.The Ghost's Tale - Olivier (1948)

Olivier's version of the Ghost is an off-putting creature. Everything about it makes you uneasy, which is at once its power and its weakness. It is very hard to empathize with this stiff-faced puppet, with its badly synchronized lip movement and strange whispering tone. Sometimes, the blurry lenses and obscuring smoke are quite effective at creating this otherworldly being. At other times, it just looks like a great big smudge. The technical considerations tend to create some very static shots through this whole sequence.
Olivier changes it up near the halfway point, as the story of the murder is told, and we're allowed to see it, or at least a version of it, when the camera moves in on the back of Hamlet's head. This avant-garde maneuver is ambiguous. On the one hand, you'd think that it would be Hamlet's imagination because the flashback is in his head. However, the camera's behavior in the film is often that of a floating spirit, moving around Elsinore looking for action, often from strange vantage points. Though the Ghost is standing in front of Hamlet, there is something about the flashback that makes it the Ghost's and not Hamlet's.
Hamlet Sr. sleeps through the poisoning and wakes up when pain strikes. The poisoner's face is obscured by the mists around the scene. When the king turns around and sees his murderer's face, so do we (if through a haze). Now, Hamlet already knows the identity of the poisoner because the Ghost prefaced his tale with this revelation. Why then don't we see Claudius from the start of the memory? We are definitely experiencing the murder from the king's point of view, so could this be his spirit entering Hamlet's mind and showing him these images? It's perhaps no wonder it unhinges his mind. There's a nice editing choice as the vision ends. All we see is the king's hand reaching for its killer and then dying. Hamlet reaches for it as the two scenes are mixed together, as again a director attempts to connect father and son through the veil of death.

The Ghost leaves as he arrived, with tell-tale pulsing heart beats that affect the camera as much as the sound. Hamlet swoons and keels over. The camera (again, I suspect the Ghost's spirit) flies up and comes through clouds. When he awakes, he's whirling his arms about, throwing his sword down and going from manic to despondent at a second's notice.
Since Hamlet is alone with his thoughts, it seems like Olivier has chosen to make him mad at this point. He's not (entirely?) faking it for the benefit of the Court later.