Focus Pulls

My interpretation of  Focus Pulls is essentially the same as Depth Of Field, but instead of only one area of the scene remaining obscured and blurred a switch occurs in which both areas swap obscurity i.e. the area that was once clear becomes blurry and vice versa.

I believe this was used in this scene once again to only display what is important/necessary in the scene, the switch over initially from Moriarty to Sherlock wielding a handgun also emphasises his motivation and mindset in which he may or may not pull the trigger. This results in a more entertaining and tense scene as the audience initially remain unsure of Sherlock's decision in this stressed scene,