The distance between the nearest and furthest objects that are visually in focus in an image.
Depth of field (DOF) is most often referenced in photography and film. There is a synonym; focus range.
The point of focus for a lens is in fact very exact. However, from that focus point, the change in sharpness will change until the difference becomes perceptible. Of course, these observations are made under normal viewing conditions.
DOF can be used to emphasize a subject, at a focus point, by de-emphasing the foreground and background, which will appear out of focus.
The focus of the lens of a camera is an exact point and because the lens is round the in-focus range takes the form of a circle. The largest circle from the point of focus is called the “circle of confusion”.
In film photography,
- The focus distance in feet (ft) or meters (m)
- The f-number
In the image above you can see my Nikon Nikkor 20mm lens set at f/11, which indicates a depth of field of 0.4 to 0.7 meters, after I have sighted on my subject.
Below is an image of my Nikon Series E 50mm lens set at f/11, which indicates a depth of field from about 4.5 to just under 7 feet, after focusing on my subject (at about 5.5 feet).