what is dof

Depth of field (DOF) is a term used in photography to describe the distance between the nearest and farthest objects in a photo that appear acceptably sharp. It is controlled by the lens aperture diameter, which is usually specified as the f-number (the ratio of lens focal length to aperture diameter) . Reducing the aperture diameter (increasing the f-number) increases the DOF because only the light traveling at shallower angles passes through the aperture, and the light rays are within the acceptable circle of confusion for a greater distance. Many lenses include scales that indicate the DOF for a given focus distance and f-number. The DOF is not a hard boundary between sharp and unsharp since defocus is produced gradually. The distance between the camera and the first element that is considered to be acceptably sharp is called the DOF near limit, while the distance between the camera and the furthest element that is considered to be acceptably sharp is called the DOF far limit.