Maximising DOF

Ashok Kandimalla has been in the photographic field for over three decades and has extensive experience in both film and digital photography. Being an electronics engineer by profession and a photographer, he possesses a unique and deep insight into the technical aspects of digital photography and equipment. He has published more than a 100 articles on photography and some of his writings have also been published in the well-known international magazine Popular Photography. An avid collector of photographic books and vintage cameras, Ashok has a keen interest in the history of photography and a passion for sharing his knowledge on photography through teaching and writing. He is the only Indian photographer to be featured on the Nikon Centenary website. He is presently working as a Management and Engineering consutant.

- Ashok Kandimalla

A photograph whether displayed on a monitor or printed on paper is flat without any depth and hence is two dimensional (2D). Contrary to this, the world we live in is in three dimensions (3D). Thus, whenever we take a photograph, we ‘project’ (transform) a 3D scene into a 2D image. There are many types of projections but the one that occurs when we take a photograph is called the ‘perspective projection’.

The important characteristic of this is that objects that are close to us (in the foreground) look bigger while those that are far away (in the middle or background) look smaller. This property is used by all good photographers to create a sense of depth that is otherwise absent in a flat 2D photograph (Picture 1). In addition, a high quality landscape picture must be sharp from foreground to background.

It is now time to recap the concept of depth of field or DOF. When you focus on a point, only one plane (that is, all the items that are at the same distance as the point) will be in precise focus. However, the human eye will find that there is a zone of acceptable sharpness that extends from the front of the point to beyond it. This zone is called the DOF. So, as mentioned, to get a good ‘sharp all through’ landscape photograph we need to maximize DOF to get all the objects in focus.

DOF depends mainly on three factors, magnification, aperture, and circle of confusion