What is Depth of Field?
When we adjust our camera’s lens to focus on a subject it will only achieve perfect focus at one particular distance; anything in front or behind this point will be blurred to a greater or lesser degree.
Depth of field refers to the area around the perfect focal distance which appears acceptably sharp.
What Affects Depth of Field?
Depth of field is affected by three main factors:
- Lens aperture diameter
- Focal length
- Distance from the subject
Aperture and Depth of Field
The aperture determines the diameter of the beam of light that the lens admits. The wider the aperture, the wider the beam of light. A wider beam is more susceptible to depth of field effects than a narrower beam.
Using a wider aperture produces a shallower depth of field; using a narrower aperture gives a greater depth of field.
Focal Length and Depth of Field
Focal length is a measure of how much the lens magnifies a scene. The lens also magnifies differences in focus.
A longer focal length magnifies focus differences, resulting in a shallower depth of field.
Focus Distance and Depth of Field
The closer the subject is to the camera, the greater the relative distance from the front to the back of that object. A high relative distance gives a corresponding reduction in how much of the object appears in focus.
Controlling Depth of Field
|To Increase Depth of Field||To Decrease Depth of Field|
|Narrower aperture||Wider aperture|
|Shorter focal length||Longer focal length|
|Move away from subject||Move towards subject|