What is the effect of Branagh's frequently looking directly at the camera? Why does the director, Parker, use this device?This is question is...

The short answer here is that the medium of film allows
Branagh to speak directly to the audience, looking straight at the camera.  The film
audience differs from the stage one in that the director makes the conscious choice of
what the audience sees.  The audience has little choice but to witness what is being
given.  In the modern depiction of Iago, Branagh knows a couple of things.  The first is
that this is one of the most difficult of Shakespearean villains to portray.  As
Shakespearean scholar A.C. Bradley states, " evil has nowhere else been portrayed with
such mastery as in the evil character of Iago."  Branagh knows this and realizes that
with a modern audience, who is fairly adroit at understanding the machinations of a
devious mind, he has to be able to add something else to his characterization of Iago.
 He does so in trying to bring out the different layers to Iago in the film.  The latent
homosexual theme is one that is not as apparent in a straight reading of the text, as
well as other themes such as the "honorable servant done wrong."  In staring at the
camera and in what seems like directly speaking the audience, Branagh is able to bring
out in the audience these different layers, forcing them to look at the character of
Iago in different ways.  Parker is able to trap the audience in being able to examine
this character, the way one reconstructs the scene of an accident, with layer upon layer
of analysis and reassessment.  This only happens when Branagh lays into the audience,
occasionally directly looking at the camera as he speaks.