Focusing effects, such as deep focus, shallow focus, and rack focusing, are used to direct the viewer’s attention to particular subjects and/ or actions in a frame. You’ve most likely seen them used before in films and on TV, but perhaps you don’t know exactly what each approach is or what they’re used for. Read on for some basic knowledge and the differences between them.
Whenever all of the subjects in a frame, both in the foreground and in the background, are crisp clear and are in focus, this is known as deep focus. Imagine a scene in a park where there’s plenty of action taking place and everything is in focus. In the foreground, a couple snuggle on a park bench and directly behind them are children playing on the playground; and still even further in the background is a man playing Frisbee with his dog in a field. Seeing this action all at one time may be the intention of the filmmaker; and thus the viewer may choose to pick, if not all, which plane of action they choose to watch. (This is known as a realistic approach used in cinema; after all, isn’t this how it actually is if we were really there?)
But, let’s imagine in this scene something dramatically important taking place that needs to be highlighted; for instance, one of the children on the slide falls and bumps his head. If the camera isn’t focused on this plane of action, assuming the filmmaker intends for the viewers to witness the accident, the viewers most likely will not catch this. This leads us into the next term ...
Don’t let the word ‘shallow’ mislead you. Some may assume shallow means focusing on subjects in the foreground, but this is not necessarily so. When using this terminology for camera focus, shallow simply means focusing on a subject, whether in the background or foreground, resulting in everything else being thrown out of focus. This plane of focus is used to direct a viewer’s attention toward something or someone.
Let’s go back to the park scene. To make the action of the kid’s accident noticeable to the viewers, let’s say all of a sudden, just before the child slips, the camera immediately focuses on the child behind the couple in the foreground. This immediate shift in focus, whether the viewers were watching the couple in the foreground or the man with his dog in the far background, will bring their attention to the child’s accident. This is a technique used often to highlight a certain subject or action taking place in a camera frame and it must only be used for a purpose, or otherwise it will be distracting to your audience and will not make sense.