Controlling Depth Of Field
Here the greatest possible depth of field
was used to keep everything sharp from the fighter's needle nose to the background.
This photo of a page from a book shows how
shallow depth of field can be when you get close to a subject.
Click to explore how the aperture affects depth of field.
Sharpness—or the lack of it—is immediately noticeable when you look at a photograph. If you are making a portrait, you want only the person to be sharply focused, but not a distracting background. In a landscape, on the other hand, often you will want everything sharp from close-up rock to far away mountain. Once you understand how to control depth of field, you will feel much more confident when you want to make sure something is—or isn't— sharp.
To control depth of field, you have three factors to work with.
- Aperture size. The smaller the aperture, the greater the depth of field. The
larger the aperture, the shallower the depth of field.
- Camera-to-subject distance. As you move father from the subject you are
focused on, you increase depth of field. As you move closer, you decrease it.
- Lens focal length. Using a wide-angle lens or zooming out increases depth
of field. Using a long lens or zooming in decreases it.
Each of these three factors affects depth of field by itself, but even more so in combination. You can get the shallowest depth of field with a lens zoomed in on a nearby subject using a large aperture. You get the greatest depth of field when you are far from a subject, with the lens zoomed to a wide angle, and using a small aperture.
Here the camera's depth of field was just
deep enough to keep the bird in focus. Parts of the image closer to the camera and further away become increasingly less sharp.