Photography Basics 3 – Depth of Field

Depth of field (DoF) refers to how much of a picture is in sharp focus in front of, and beyond, the part of the picture you’ve focussed on by changing the aperture setting of the lens. You can use it to guide your viewers eye to where you want them to look. It’s one of the three factors that determine the exposure of a picture (the others are shutter speed and ISO, the preceding and following posts respectively in this series).

There are three main factors to bear in mind about depth of field

A) The amount of light entering the lens (measured in f stops on your lens). For example f2.8 is a wide aperture so more light comes through the lens giving less depth of field, whereas f16 is a small aperture so less light comes through the lens giving more depth of field

B) The shorter the focal length of a lens the greater the depth of field appears to be at the same aperture. For example a 24mm lens at f8 will appear to have a greater depth of field than a 300mm lens at f8

C) Roughly one third of the picture will be in focus in front of the point of focus and two thirds will be in focus beyond the point of focus at any given aperture

Have a look at pictures 1 to 3 (you’ll see the differences more clearly if you view them on your monitor or rotate your phone to landscape).

You can also use a shallow depth of field to create depth to a picture (No. 4) by throwing the foreground and background out of focus.

If you’d like to know more about this and other aspects of photography there are more details here