Scale-focus
Encyclopedia
Scale focus, or zone focus, is a type of focusing system used by many inexpensive camera
s from the 1940s and 1950s. These cameras have an adjustable focus, but lack a focusing aid such as a rangefinder
. It is necessary to determine the distance to the subject and set the focus using a scale printed on the lens. If you are good at estimating distances, or have a tape measure
at hand, you can get precise, sharp focus with one of these cameras.
Today the term "zone focus" is used, particularly in North America, to the technique of setting a fixed focal distance (turning off autofocus
), and often fixed aperture, hence fixing the depth of field
, and then taking photographs at that distance; the DOF can be read off of the DOF scale on the focus ring, hence the term "zone". This is particularly used in street photography
, to allow rapid and candid "shooting from the hip" (shooting without composing in the viewfinder) and avoiding autofocus lag. Zone focusing is also useful for pet action photography, where the time delay of focusing may be unworkable.
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...
s from the 1940s and 1950s. These cameras have an adjustable focus, but lack a focusing aid such as a rangefinder
Rangefinder
A rangefinder is a device that measures distance from the observer to a target, for the purposes of surveying, determining focus in photography, or accurately aiming a weapon. Some devices use active methods to measure ; others measure distance using trigonometry...
. It is necessary to determine the distance to the subject and set the focus using a scale printed on the lens. If you are good at estimating distances, or have a tape measure
Tape measure
A tape measure or measuring tape is a flexible form of ruler. It consists of a ribbon of cloth, plastic, fiber glass, or metal strip with linear-measurement markings. It is a common measuring tool. Its flexibility allows for a measure of great length to be easily carried in pocket or toolkit and...
at hand, you can get precise, sharp focus with one of these cameras.
Technique
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
), and often fixed aperture, hence fixing the depth of field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
, and then taking photographs at that distance; the DOF can be read off of the DOF scale on the focus ring, hence the term "zone". This is particularly used in street photography
Street photography
Street photography is a type of documentary photography that features subjects in candid situations within public places such as streets, parks, beaches, malls, political conventions and other settings....
, to allow rapid and candid "shooting from the hip" (shooting without composing in the viewfinder) and avoiding autofocus lag. Zone focusing is also useful for pet action photography, where the time delay of focusing may be unworkable.