12-1 Focal length is technically, one design parameter of a lens, expressed in millimeters. The name of any particular lens, such as "a 40mm lens".

12-2 One broad group is is the Iris almost fully closed f/16.

12-3 Depth of field is the distance, in front of and behind the plane on which the lens is focused, in which objects in the image sharp. A scene that looks perfectly sharp in wide angle may turn soft when you zoom to telephoto.

12-4Perspective is the illusion of depth in the picture, the apparent distance from the camcorder to the farthest part of the scene.

Perspective is the illusion of depth in the picture, the apparent distance from the camcorder to the farthest part of the scene