Depth of field (DoF) is the area between the nearest and farthest points from the camera that are acceptably sharp in an image. A deep DoF means all or most of your photo will be in focus, including the foreground, subject and background. Use a deep DoF in group photos, landscape shots and when elements in the background or foreground add to the message the photo is attempting to communicate. A shallow DoF means more narrow range will be acceptably sharp in the image. Shallow DoF is good to use when you want to isolate your subject from their surroundings, such as in a portrait or when elements in the background or foreground may be distracting.
You can affect the depth of field by changing the following factors: aperture, the focal length and the distance from the subject.
The aperture is the opening created by a set of overlapping metal blades, known as the diaphragm, inside a photographic lens. This opening controls the amount of light coming through the lens. The wider the aperture, the less depth of field you capture. The smaller the aperture, the deeper the depth of field.
The focal length of the lens determines the image magnification. The wider the lens, the shorter the focal length. This allows you to capture a wider depth of field. The longer or more zoomed in the camera lens, the less depth of field you capture.
Distance to Subject
Distance to subject refers to the length between the camera and the focus of the image. The closer the camera is to the subject it is focusing on, the narrower the depth of field will be. Inversely, the farther away the subject is from the camera, the wider the depth of field will be.
How the Factors Affect the DoF
The following graphic illustrates how changing these factors: aperture, focal length and the distance from the subject affect the depth of field.
See how each of these factors are applied in the depth of field examples below:
Shallow depth of field is best applied to photos that need to:
- create intimacy between the subject and the audience.
- hyper-focus on a subject's facial expression or an object's texture.
- separate the foreground from the background by blurring distractions.
Medium depth of field is best applied to photos that need to:
- tell a story between the subjects and their environment while keeping a respectable distance.
- focus on 1-5 subjects or objects.
- keep the subjects in the foreground while blurring the background.
Deep depth of field is best applied to photos that need to:
- convey a sense of grandeur such as a large crowd or group of objects.
- immerse the audience in the environment.
- focus on both subjects in the foreground and background.