Photographers and viewers alike will commonly agree that photos with a sharply focused subject and a blurred background appear more professional than those where everything is equally in focus.
Typically, this is a technique done 100% in camera, and can be achieved by choosing the proper camera and lens settings and by composing the shot a certain way. This look is known as shallow depth of field.
The primary factors which determine depth of field in a photo are aperture, focal length, and distance. In addition, the photographer can blur the background during post-production in Photoshop, but caution should be given when using this method to not make it look noticeably fake.
What Is Depth Of Field?
Depth of field (DOF) is defined as how much of an image is acceptably in focus (sharp). The photographer should be deliberate in creating an image with the proper depth of field, depending on the genre or the end goal of the image.
Generally speaking, portraits look best with a shallow depth of field (where the subject’s face is the sharpest part of the image and other elements are blurred), and landscape images look best with a large depth of field (where everything is in focus).
Images with a shallow depth of field tend to make the subject stand out much more from the background, and the photographer is able to take attention away from objects in the background that may be distracting or not pleasant.
In-Camera Techniques for Creating a Blurred Background in a Photo
Creating photos with a shallow depth of field is best done in camera, using the aperture and focal length settings, as well as certain methods of composition.
Technique #1: Using a Wide Aperture
The aperture is the opening in the lens which allows light into the camera, measured in f-stops.
The size of the aperture opening is a determining factor in depth of field. A larger opening (small f-stop, like f/2.0) will give a shallower depth of field than a narrow opening (large f-stop, like f/16). Keep in mind that the aperture also controls the amount of light entering the camera sensor, so this should be taken into consideration when adjusting each setting for proper exposure.
Portrait photographers often prefer lenses with a widest aperture of f/1.2 to f/2.8 because these allow them to create portraits with a heavily blurred background.
Photographers shooting landscapes, architecture, vehicles, or other scenes may prefer shooting at a narrower aperture like f/8 or f/16 so that all parts of the image are in focus.
Technique #2: Using a Long Focal Length
The focal length is the distance from the lens to the camera’s sensor (measured in millimeters) when the subject is in focus. Lenses come in many focal lengths, and will either be a fixed focal length (prime lens) or a variable focal length (zoom lens).
A photo taken using a longer focal length will “compress” the subject, creating a shallow depth of field and blurred background. A photo taken using a shorter focal length will cause all or most of the elements in the photo to be in focus.
Lenses with short focal lengths like 24mm or 35mm are ideal for large group photos where people are posed in different positions where everyone needs to be in focus, as well as to fit the entire group in the frame.
Technique #3: Increasing Subject-to-Background Distance, and Technique #4: Decreasing Camera-to-Subject Distance
Distance is not a camera or lens setting, but is a method of composition which is another determining factor in how blurred the background will be in a photo.
Increasing the subject-to-background distance will cause the background to be increasingly blurred the further the subject is from the background. To achieve this look, photograph the subject with a far distance from the background.
Decreasing the camera-to-subject distance will cause the background to be increasingly blurred the closer the subject comes to the camera. If you want to see more details of other elements in the photo, photograph the subject closer to the background.
If a photographer wants to take a group photo where they need to use a small aperture and short focal length to ensure everyone is in focus, but still wants to make the background appear blurred, finding an area where the background objects are a further distance from the group of subjects is the solution.
These techniques can work alone or together. To achieve the most blurred background possible, the photographer can shoot at a wide aperture, a long focal length, a far subject-to-background distance, and a close camera-to-subject distance. One must always be careful however to make sure all parts of the subject that need to be are sharp and in focus.
Post-Production Techniques for a Blurring the Background in a Photo
Sometimes a photographer may want to add some background blur after the fact. While this isn’t the ideal method, it can be done where it still looks convincing enough for the viewer to not know it was done in Photoshop. It can be a useful method when there are factors that limit the photographer’s ability to create a shallow depth of field.
Technique #5: Gaussian Blur and Layer Masks in Adobe Photoshop
The best method is by utilizing layer masks and the Gaussian blur tool. The image should be opened and a duplicate layer created. A slight Gaussian blur should be applied to the new image layer, and then a layer mask must be created. Using the brush tool in black, the subject must be “painted” over to remove the added blur.
It will take some careful work to refine the edges of the layer mask. Because natural depth of field blur falls off gradually in front and behind the subject, the layer mask will need to be painted off and on at varying opacity settings so that the focus fall-off is subtle and gradual.
Achieving a blurred background in photos is not difficult, as long as you understand how to control the settings on your camera and know how to compose the shot.