Guess focusing

From Camerapedia.org

Guess focusing was the most common way of focusing for many years. You had to estimate the distance to the subject yourself, and set the focusing ring or focusing lever accordingly. You were somewhat assisted by the depth of field scale. Usually the lens was fixed and its aperture was not too big, typically f/2.8 as a maximum. It is not possible to guess the distance with enough precision for a larger aperture.

These cameras were usually more expensive than the fixed focusing ones, but cheaper than the rangefinder or reflex type.

A variant was scale focusing or zone focusing, used on cheaper cameras, targeted at people who would not take the trouble to guess a distance in meters or feet. Symbols on the focusing ring, (usually "one person", "a group of people" and "a mountain") indicated the most probable setting for your picture depending on the subject.

This type of camera has evolved to become the point and shoot cameras, equipped with an autofocus device. You do not have to guess the distance yourself, and of course the operation is faster. There are several methods used, see autofocus.