Focus pulls

Definition of a focus pull: A focus pull is a creative camera technique in were you change focus during a shot, adjusting the focus from one subject to another. The focus pull is useful for directing the viewer's attention. This is often used in drama dialogues — the focus shifts backwards and forwards between the people speaking as each one talks they become the main subject and focus point. Example of a focus pull (about 3 minutes in):
 The focus pull is used here so that you can see the Moriarty who may be shot in detail and then the gun that he might be shot with in detail. This adds tension and suspense to the audience as they wait to see if Sherlock will shoot.