Depth of field is the range of focus in a shot – whether the whole scene is in focus or if the camera if only focused on one part.  A shallow focus, also called a small depth of field, is when only one part of the scene is in focus while the rest is blurry and unfocused. A deep focus uses a large depth of field, so the whole of the scene is in focus for the audience.

An example of a small depth of field is in The Circle (dir. James Ponsoldt, 2017).

In this scene, only Mae is in focus, while everyone else sitting along the row is blurred. The director has chosen to use this shot so that the audience know that they should be focusing on her. This shot emphasises that she is the main character. It causes the audience to pay close attention to her face and her facial expressions, so they understand how they should be responding to the scene. This type of depth of field is used by directors in scenes when one character is important, and the audience need to be directed to look at them. It is useful because any irrelevant things that are happening in the background can be out of focus, so the viewers don’t look at it.  If the director had wanted the audience to look at everyone in the scene equally, then he would have chosen to use a larger depth of field, so that they would all be in focus. This kind of depth of field is often used to show characters who all have equal importance in the scene. This means that the viewers will look at everyone rather than just focusing on one section.