Zone focusing, or ‘scale focusing’, is the systematic pre-focusing of a lens at specific distance and aperture to achieve a sharp image. Arguably one of the most effective methods of focusing your camera, zone focusing has been used by street photographers for decades allowing them to capture that fleeting decisive moment. This has been the go-to for rangefinder shooters since the beginning of the type.
Even with modern autofocus systems in the latest cameras, it still takes a brief moment for the camera to ‘lock on’. Not relying on automation, zone focusing utilizes a deep depth-of-field to ensure your camera will be in focus before it even reaches your eye. Factors that affect depth-of-field included aperture, focal length, and sensor size.
A smaller aperture, shorter focal length, and smaller sensor size will increase depth-of-field. In zone focusing, especially with street photography, a high f-stop number (between f/8 and f/16) and a wider lens (usually 28mm and 35mm on full frame) are frequently used.
Photographer David Coleman produced a brief video explaining exactly what zone focusing is, and different method to achieve it.
In one method, setting your “zone of focus” is as simple as lining up the aperture with a selected distance marking on your lens (if it has them) to determine the scale of what will be in focus. Some mirrorless systems are focus-by-wire, where the focus is controlled electronically, and a scale is not printed on the lens. Apps like Hyperfocal Pro for Android or Simple DoF Calculator for iOS come in handy to help calculate the zone of focus for smaller sensor cameras.
Zone focusing allows you to completely concentrate on the scene and photo you are about to make. It allows you to become apart of your surrounding. With practice, you know the area that will be in focus and as long as the action takes place in the predetermined range, the scene will be in focus.