Understanding how to control depth of field is one of the most important skills a photographer should master. Knowing how to make parts of your composition sharp, while other parts of the image fall out of focus is not only a technical skill to have in your “tool bag” but also gives you artistic and creative control over your images.
In basic terms, depth of field or focus range is defined as the front-to-back zone of acceptable sharpness within a photo that will appear in focus.
The zone will vary from photo to photo. If an image has a small area of focus, we call this “shallow” depth of field. Usually, we see this as the background falling out of focus while the main subject of the image is in sharp focus. However, the out of focus area does not have to be the background, it can be any portion of the photograph. Often this technique is used in portrait photography to isolate the subject from its environment. You may have heard of background blur referred to as “bokeh.” Conversely, when an image is in focus throughout much of its foreground, mid-ground and back ground, we call this “narrow” or “deep” depth of field. We often use narrow depth of field in landscape photography.
There are a few basic components that you’ll need to establish to create an image with shallow depth of field. They are: aperture, distance to subject, focal length and distance from background to subject.
For a nice blurry background, you’ll need to choose a large aperture. Remember the smaller the number, the larger the aperture. So dialing in a f-stop of 2.8 or 4.6 is going to give a more shallow depth of field than using a f-stop of let’s say f/11 or f/16.
2. Distance to subject:
The closer the focused subject is to your camera, the more the background will become out of focus. However, change the focus to a subject that is farther away from the camera and more of the area in front and behind that subject will be in focus even if you did not change the aperture or any other setting.
3. Focal length:
Telephoto lenses work best for creating a shallow depth of field. A telephoto is defined as any lens longer in focal length than 50mm. Zoom telephotos or a prime lens over 50mm both work great for blurring backgrounds, but try photographing with a wide-angle lens and you’ll find your background is in good solid focus.
4. Distance from the background:
Placing space between your subject and its background will also help you create a shallow depth of field. Imagine you are photographing a person, and they are leaning against a wall. Even if you shoot at f/2.8, both the person and the wall will be relatively in focus. Simply ask your subject to step at least six feet away from the wall and now you are back to creating a nice creamy blurred out background.
Shooting with a wide open aperture is the easiest way to manipulate depth of field, but remember it’s not the only way. To achieve lots of that creamy bokeh, you’ll need to not only use a large aperture, but also get close to your subject, use a lens with a long focal length and separate your subject from its background. Sensor size is also a factor affecting depth of field. The larger the sensor, the shallower the depth of field overall. That’s why you don’t get blurred out backgrounds when you photograph with a point and shoot camera.
Now that you have learnt how to control depth of field, you can use it to create greater impact in your images. Use it to draw the viewer’s eye to a particular part of your photo. Or use it to blur out a cluttered and unsightly background.
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