Depth Of field

In photography one of the most important thing we should concider is Depth of field.When a particular subject is recorded on photographic media, some other entities present in front and at the back of the main subject are also recorded apparently sharp.The subject range that renders apparently
sharp on photographic media is know as the depth of field.This is based on the smallest entity that human eye can resolve - known as the circle of confusion.

There are three main parameters available to the photographer to control depth of field.

• The iris diameter of aperture. As the iris diameter reduces, the viewing angle of the light cone also is restricted, in creasing the DOF.
• The subject distance. Similarly increased subject distance also makes the projected angle on the lens narrower, increasing DOF.
• The focal-length of the lens used. Since shorter focal-length looks at a wider angle (large no. of picture elements), per element projected angle is narrower.

Shallow depth of field

Only the foreground is in focus.

Great depth of field

The image is in focus from the

foreground to the background.