In Hamlet Act III scene iii Claudius is found "praying" and Hamlet comes upon him doing so. Does Claudius know Hamlet is there?
I ask this because a while ago I was a part of this play in the role of the villainous King. A fellow actor of mine told me to try playing out this scene revealing that Claudius knowing Hamlet was there when he decided to sit down to pray: "Bow, stubborn knees; and, heart with strings of steel,/Be soft as sinews of the newborn babe!/All may be well."
He told me that Claudius would be aware of Hamlet's presence through a feeling. Just the closeness of these two main characters, who are enemies, would create a stir within each of the other. And Claudius, too, is aware that Hamlet knows he murdered his brother (Play within a play scene).
Is it plausible that Claudius would sense Hamlet's hatred and want of revenge?
Well, according to the stage directions in the play, Hamlet enters after Claudius gives his soliloquy, which is intensely spiritual and focused on his soul and the afterlife. Observe:
You can't have Hamlet step on those lines with an entry. They are full of apostrophes to pain and suffering, and to have another body on stage will diminish their power and relevancy.
Hamlet enters and says his monologue, so the audience should be watching and listening to it, for it is a response to the soliloquy. You can't have the audience's eye drawn to Claudius acting like he knows Hamlet is there. It's just too hoaky.
Plus, there's not enough time. Claudius only has a couple of lines after that, and then he's gone. Not to mention that when Claudius says, "My words fly up...," he's talking about the silent ones in prayer, so he's obviously busy praying. His praying is dramatic irony enough: the main thing is that we know Hamlet is there, not him. You can't have him praying and noticing Hamlet. Too busy.
The scene is about spiritual crisis for both Claudius and Hamlet, not about the closeness of two actors. It's about Claudius worrying about his soul, maybe for the first time. Hamlet, too, is worried about Claudius' soul: he doesn't want to send him to heaven, only hell. He realizes that it's spiritually not the right time to kill, which is ironic and funny.
Let the audience focus on the words, not some non-verbal action on stage. Shakespeare's all about the language, not the action, and certainly not subtext and subtleties. I wouldn't diminish those words for anything. That's what a movie adaptation is for. You might be able to do it with a close-up, but not on stage, not even in the round. Too much can go wrong.
There is no indication in the play that Claudius knows of Hamlet's presence when Claudius is in the chapel praying. More evidence points to a lack of awareness on the part of Claudius than an awareness of Hamlet's presence. Despite the fact that Claudius knows Hamlet suspects him of having murdered King Hamlet, it doesn't make sense for Claudius to purposely let Hamlet hear him confessing his crime. What benefit would there be for Claudius? He isn't contrite because he says he can't be truly sorry since he still has the benefits of his crime - the throne and Gertrude (3.3. ll. 51-55). If he wanted Hamlet to hear him, it would be more sensible to show complete sorrow and beg for foregiveness. I'm not sure that Claudius and Hamlet share a special bond or closeness that would allow Claudius to "feel" Hamlet's presence. I don't know of any proof of that connection.
Most certainly Claudius did not see Hamlet when he tried to pray and was not aware of his presence.
The stage direction at the beginning of Act III Sc.3 reads, "A Room in the Castle." The scene does not take place in any chapel.
After an intense struggle within himself as expressed by Claudius in his tortuous soliloquy, he kneels down to pray, and the stage direction reads, "Retires and kneels, Enter Hamlet."
Hamlet on seeing Claudius all alone and without his body guards, straightaway draws his sword to kill him but decides against it reasoning within himself that he will only be doing Claudius a favor by sending him to heaven:
If Claudius had seen Hamlet with a drawn sword ready to assassinate him he would have either defended himself by drawing his own sword or he would have called for his body guards. That he didn't do so clearly indicates that Claudius was oblivious to Hamlet's presence.