Using Depth of Field to Your Best Advantage in Your Photos
Depth of Field (DoF) is the distance between the nearest and farthest objects that are in acceptably sharp focus in an image. There are three main factors that affect the depth of field:
- Aperture (F-Stop)
- Distance from the subject to the camera
- Lens focal length
The use of Aperture to control the DoF:
The Aperture (F-Stop) is the size of the opening in the lens, which controls the amount of light that reaches the sensor. Using the aperture is the simplest way to control the depth of field in your photo. As E. David Luria teaches in his F-Stops and Shutter Speeds safari, a large aperture (f/2) will make 2 people in your photo appear in focus (a shallow or small DoF); and a small aperture (f/22) will make 22 people in your photo appear in focus (deep or large DoF).
The use of Distance to control the DoF:
The closer your subject is to the camera the more shallow the DoF becomes. To increase or deepen the DoF, move further away from your subject.
The use of the Focal Length of a lens to control the DoF:
Focal Length is the capability of the lens to magnify the image of a distant subject. While the calculations can get complicated, the result is that using a longer focal length will produce a more shallow DoF.
One thing to keep in mind is that the DoF is not equally distributed in front and behind the focus point in the image. It is usually about one third in front and two-thirds behind, but as your focal length increases, the DoF becomes more equal.
F/14, 160/sec, ISO 800,
F/5.6, 1000/sec, ISO 800,
Learning how all three factors work together to control the DoF will enable you to have more creative control over your photos.
For instance, when photographing wildlife, to make the subject stand out from its surroundings, use a long lens and a large aperture. In general, you are usually not very close to the subject, so this combination of factors will produce a shallow DoF.
If you want everything in your photo to be in focus, use a technique known as hyperfocal distance, which means that your DoF will extend from half the distance to your focal point to infinity. There are calculators that can be used to find the hyperfocal distance, but you can also use this rule of thumb: focus one-third of the way into the scene, and use an aperture of f/11 or higher with a wide angle lens to maximize the DoF.
An extremely shallow DoF is often used in Macro photography. Many times macro images are made in low light situations, so it is necessary to use a tripod to keep the image within the focal point of the shallow DoF and also to minimize camera shake if a longer shutter speed is necessary. Increasing ISO may also be necessary to achieve a properly exposed photo.
Most digital cameras on the market today have a DoF preview button, which will enable you to see what the image will look like using the current settings. Don’t be afraid to experiment with the combination of Aperture, Distance from the subject to the camera, and lens Focal Length to achieve the DoF you envision in your photos, Send your best photos to us! We’d love to see them!