Depth of field refers to the limitation of perceived sharpness in a photograph. The depth of field increases with the amount of sharply defined picture from front to rear. A shallow depth of field image has a shallower, more concentrated depth of sharpness.
In photography, using depth of field with care may be quite useful. It accomplishes this by encouraging viewers to focus only on sharp objects by employing a short depth of field. It is painful for our eyes to view fuzzy images, therefore we prefer to concentrate our attention on the crisp areas of an image. This makes the other, less crisp portions of the image look fuzzy and un-interesting. This use of a tiny depth of focus is quite effective in portrait photography. As long as the eyes are clear, most other faults may be ignored. In nearly all portrait photography, eyes are the first feature that people and animals glance at, thus they need to be crisp.
Landscape photography is at the opposite end of the depth of field spectrum since the vast majority of these images require a very long depth of focus. This is due to the fact that landscapes usually aim to capture a subject as we truly see it, and a deep depth of field often draws the viewer in.
Two methods exist for managing depth of field. The most often used technique is aperture control. Larger values (F22) indicate smaller apertures, which result in a greater depth of field. The smaller the value, such as F2.8, the bigger the aperture; the narrower the depth of field. Every aperture in between has a depth of focus that is precisely proportionate to its selected location on the scale. The second method to adjust depth of field is to use a camera or lens that has a tilting mechanism that lets you tilt the lens forward or backward. This allows the focusing plane of the lens to be tilted further toward the plane of focus of the subject, resulting in a markedly enhanced depth of field without adjusting the aperture. One of the primary arguments in favor of tilt lenses or bellows-style cameras is this. Such a camera or lens allows for considerable control over the depth of field at any aperture.
The depth of field is influenced by both the lens’s focal length and the type of camera it is used on. For example, the depth of field of a wide angle lens is nearly always significantly bigger than that of a telephoto lens. A 600mm telephoto lens has an extremely small depth of field, which remains relatively limited unless the lens is focused on distant subjects. On the other hand, a 14mm lens, or any other wide angle lens, essentially requires no focus. On the other end of the spectrum, macro lenses are made to focus extremely closely on objects. Once you start to concentrate close and get close to the subject, the depth of field again becomes quite short. As you get closer to the subject, the depth of field gets less, and in really close-up photos, even the slightest movement can totally blur the picture.
