Depth of Field

The depth of field is the distance between the nearest and furthest in-focus objects in an image. A narrow depth of field will have a very narrow area in which objects will be in focus. A wide (or large) depth of field will put most elements of the image in focus. 

Depth of field is influenced by several camera settings including aperture (f-stop) and the lens focal length.

Lower f-stop settings (f/1.2 - f/2.8) have shallow depths of field.

Higher f-stop settings (f/11 - f/32) have wider depths of field.

Longer focal lengths (like the 105mm setting on the Canon EF 24-105mm lens) will have a shallow depth of field.

Shorter focal lengths (like the 24mm setting on the Canon EF 24-105mm lens) will have a wider depth of field.

Turning the focus ring on the lens will adjust the position of the in-focus area, or focal point. 

The camera's distance to the subject can also influence depth of field.

The depth of field will be wider when the camera is focused on more distant subjects.

The depth of field will be shallower when the camera is focused on closer subjects.