I'm over-indulging in the Zurich Der Rosenkavalier DVD again. :D You know how uncannily Vesselina Kasarova (Octavian) dominates the stage during opera performances? Have a look just at the final duet here (starting at around 5:06 in). She has the entire auditorium so naturally covered with eye contact without even breaking character... I mean, contrast this with the gorgeous Malin Hartelius (Sophie).
The latter is a most exquisite Sophie (so poised, so amazingly sung, so still, I can't love her enough), but she theatrically disenfranchises just about all the audience on the right side of the house since she only ever looks/faces the left side of the auditorium). VK, on the other hand, has the whole hall scanned by the end of the first section of final duet, and she even does a final sweep (08:30-40) before turning up-stage and walking off with Sophie. It's so cool how she does that without breaking character. Sophie may be oblivious to your presence, but Octavian knows you're there and he isn't just singing for Sophie, but for you also ... no matter where you are in the house!
What can I say? The gal is a genius!