Focusing magnifier

FOCUSING MAGNIFIER - A simple magnifying lens that enlarges the image on a focusing screen.

-Focusing magnifier - device to magnify the optical image and aid visual focusing.
-Focusing scale - scale of distances marked on a lens focusing ring.

(More precise manual focus can, of course, be achieved with special accessories such as focusing magnifiers.) Autofocus accuracy within 1/3 of the depth of field (DOF) at the widest aperture of the lens is not uncommon in professional AF SLR cameras.

See also: Lens, Image, Type, Focus, Photography