When you’re composing your photos, one of the things you’ll need to decide on is just what parts of the picture do you want to be in focus. For example, you might want your subject to be in sharp focus at the front of the frame, while having the background out of focus. This will draw attention to your subject.

Alternatively you might want your entire photo to be in focus. You can change the focus of the photograph with the aperture of the camera, to alter the depth of field.

If you’re photographing a landscape shot you’ll want the entire picture in focus.

You can increase the depth of field by reducing the aperture, allowing you to get more of the shot in focus. If however you increase the focal length you’ll have a small depth of field, which will mean you will only have one small part of your composition in focus, for example your subject.

A wide-angle lens has a very high depth of field, allowing you to have objects very close to the camera in focus, and objects as far away as the horizon.