ABSTRACT
The periscope systems discussed here are not of the long submarine type; they are instead an extended optical system used in special-effects cinematography. Such an elongated lens system allows the cinematographer to get his very bulky camera into an otherwise inaccessible place. Some cinematographers have erroneously concluded that the depth of field is greater than that obtained from the usual depth-of-field tables given in cinematography manuals (Samuelson 1998). One reason for the apparent discrepancy is that these depth-of-field tables are measured from the lens front principal plane (a nodal point). For periscope systems, this principal plane is usually well within the body of the periscope, giving an apparently short near-depth-of-focus distance. Another reason is that these systems generally have many lens surfaces and a large distance between lens groups. Even with modern high-efficiency antireflection coatings and threads and sand-blastes finishes on the interior walls, there is still substantial veiling glare in the final image. This results in a loss of contrast that gives the appearance of enhanced depth of field.
