Far depth of field

Description

In optics, particularly as it relates to film and photography, depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Although a lens can precisely focus at only one distance at a time, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
For a given symmetrical lens, the far depth of field, is the distance from the camera up to the farest limit of the depth of field and is depended to the object distance , the lens focal length and the f-number.
(The f-number of an optical system is the ratio of the lens’s focal length to the diameter of the entrance pupil).