Depth of Field

Depth of Field

Depth of field is the zone of acceptable sharpness in an image. It is the distance between the nearest and farthest objects that appear acceptably sharp. Some images have shallow depth of field, where only a thin slice of the scene is sharp and everything else is blurred. Others have deep depth of field, where objects both near and far are in focus. Controlling depth of field is one of the most powerful creative tools in photography.

Three factors control depth of field: aperture, focal length, and distance to subject. A wider aperture like f1.8 creates shallower depth of field. A narrower aperture like f11 creates deeper depth of field. Longer focal lengths create shallower depth of field at the same aperture. The closer you are to your subject, the shallower the depth of field becomes. Understanding how these three factors interact lets you predict and control exactly what will be sharp in your image.

For portraits, shallow depth of field isolates the subject from the background. The eyes are sharp while everything else softens. To achieve this, use a wide aperture like f1.4 to f2.8, a focal length of 85mm or longer, and get close enough to your subject. Focus carefully on the eyes because that is where the viewer looks first. Even slight misfocus on the eyes can ruin an otherwise excellent portrait.

For landscapes, you usually want deep depth of field to keep everything from the foreground to the mountains sharp. Use a narrow aperture like f8 to f11 and focus about one third of the way into the scene using the hyperfocal distance technique. Be careful not to go too narrow though. At f16 and beyond, diffraction reduces overall sharpness even though depth of field increases. The sweet spot for landscape photography is typically f8 or f11.

Depth of field is not evenly distributed. About one third of the depth of field is in front of the focus point and two thirds is behind it. This means if you want maximum sharpness from near to far, you should focus slightly beyond the midpoint of your scene. Many cameras have a depth of field preview button that stops the lens down to your chosen aperture so you can see exactly what will be sharp before you take the shot.