Depth of Field

"Focal depth" redirects here. For the seismology term, see Depth of focus (tectonics). The area within the depth of field appears sharp, while the areas beyond the depth of field appear blurry. In optics, particularly as it relates to film and photography, depth of field (DOF), also called focus range or effective focus range, 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.

Video tutorial on Depth of Field

Depth of Field - Photography Tutorial for... by qasim-syed