Depth of field (DOF) in photography refers to the range of distance in a scene that appears to be in sharp focus. It is controlled by several factors, including the aperture, distance between the camera and the subject, and the focal length of the lens.

A shallow depth of field is achieved when the subject is in sharp focus, while the background is blurred. This effect is usually used in portrait photography, where the subject is emphasized by isolating them from the background. A shallow depth of field is achieved by using a large aperture (small f-stop number), such as f/1.4, f/2, or f/2.8.

A deep depth of field is achieved when both the foreground and background are in sharp focus. This effect is usually used in landscape photography, where the goal is to capture as much detail as possible from the foreground to the horizon. A deep depth of field is achieved by using a small aperture (large f-stop number), such as f/11, f/16, or f/22.

The distance between the camera and the subject also affects the depth of field. The closer the subject is to the camera, the shallower the depth of field will be. Conversely, the further the subject is from the camera, the deeper the depth of field will be.

The focal length of the lens also affects the depth of field. A longer focal length, such as 200mm, will have a shallower depth of field than a shorter focal length, such as 50mm, when shooting at the same aperture.

In summary, depth of field is the range of distance in a scene that appears to be in sharp focus. It is controlled by several factors, including the aperture, distance between the camera and the subject, and the focal length of the lens. By controlling the depth of field, photographers can create a range of effects, from isolating the subject to capturing a sweeping landscape.