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 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.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. 

Shallow Depth of Field Aperture = f/1.4. DOF = 0.8 cm	Medium Depth of Field Aperture = f/4.0. DOF = 2.2 cm	Wide Depth of Field Aperture = f/22. DOF = 12.4 cm

Lower f-stop numbers narrow the depth of field, causing the area of focus to be relatively shallow, with foreground and background parts of the image being out of focus.