Depth of field helps focus in on images

Last week, I talked about framing and the rule of thirds. This week, we’ll take a closer look at composition, and in particular, depth of field.

Depth of field is a term that is thrown around a lot in video and film.  It may sound complex, but depth of field simply refers to the part of the image that is in focus.  A deep depth of field will allow both the foreground and background of a shot to be in focus (normal vision).  This depth of field is often used for capturing objects in the distance, and for a more documentary-style film.

A shallow or narrow depth of field will cause only the foreground to be in focus.  Thus, the subject in the foreground will be in focus, while objects behind the suspect will be blurry.  A narrow depth of field is often used for portraits and close-ups.

Depth of field varies by the focal length of a lens, usually measured in millimeters.  A 50mm lens is standard for cinema and video and mimics the human eye’s focal length.  The shorter the focal length, the deeper the depth of field—thus, a 16mm would be an ultra-wide lens, and a 200mm lens have an extremely shallow depth of field.  One can often see a large, 200mm lens being used at a sporting event—they’re the huge lenses that work well for eliminating unnecessary objects from the shot.

However, a degree of distortion is created when using extremely long or shot lenses.  A wide-angle lens may stretch out images, while a telephoto lens (200mm) will compress an image.  Each lens can be used to tell a different story—the possibilities are endless.