Photography A - Z the Easy Way:
D - Depth of Field
By Eric Hartwell

When you take a picture not everything will be in focus. You may hear a lot said about “depth of field”. Don’t be confused by this terminology – it’s easy to understand and, used correctly, will help your images have more impact.

In any picture, there will be areas in the foreground (in front of you subject) and areas in the background (behind your subject) that will be out of focus. If you take a picture of your dog on the lawn, both the grass in front and the fence behind will be less sharply in focus that the dog itself.

The area between these two out of focus parts is known as the “depth of field” and can be seen as the parts of the image, from front to back, that are in focus.

But, it doesn’t stop there!

The size of the aperture that your lens is set at for the shot will determine the depth of field. A larger aperture (small number) will have a small depth of field whereas a small aperture (large number) will have a greater one.

There’s more!

The distance away from the subject will also change the depth of field. The picture of the mountain in the distance will have a large area of focus whereas the close up of the bumble bee on a flower will have a tiny depth of field.

More …

What does this mean?

You may want a large depth of field so that as much as possible is in focus. This is a technique particularly useful in landscape photography. In this case, move away from the subject and use a small aperture.

On the other hand, you may wish a small depth of field. For a close up shot (for example of the bumble bee) the shallow depth of field will isolate the bee by blurring the background. This is useful for other shots as well (for example, portraits). In these cases, use a large aperture and get closer to your subject.

It’s easy!

Eric Hartwell runs the photography resource site http://www.theshutter.co.uk and the associated discussion forums as well as the regular weblog at http://thephotographysite.blogspot.com