Depth of Field in Photography: How to Control Background Blur
Depth of field is what separates a sharp subject from a blurry background. Here is how to control it intentionally to get the look you want every time.
What Depth of Field Is
Depth of field (DOF) is the range of distance in a scene that appears acceptably sharp. A shallow depth of field means only a thin zone is in focus — the subject is sharp but the background and foreground are blurry. A deep depth of field means a wide range of the scene is sharp from front to back.
The Three Factors That Control Depth of Field
1. Aperture
This is the most direct control. A wider aperture (smaller f-number like f/1.8) produces a shallower depth of field and more background blur. A narrower aperture (larger f-number like f/8) produces more depth of field and a sharper background.
2. Distance to Subject
The closer you are to your subject, the shallower the depth of field becomes at any given aperture. Moving close to your subject is one of the most effective ways to increase background blur without changing lenses.
3. Focal Length
Longer focal lengths (85mm, 135mm) produce more background compression and apparent blur than shorter focal lengths (24mm, 35mm) at the same aperture. This is why 85mm is the classic portrait focal length — it flatters the subject and produces beautiful background separation.
How to Get the Blurry Background Look
To maximize background blur, combine all four factors: shoot wide open (f/1.8-f/2.8), use a longer focal length (85mm or longer), get physically close to the subject, and position the subject far from the background. Any one of these helps; all four together produce the most dramatic separation.
Understanding Bokeh
Bokeh refers to the quality and character of the out-of-focus areas in a photo — how the blur renders. Different lenses render bokeh differently. Lenses with more aperture blades tend to produce rounder, smoother bokeh. Most portrait photographers prefer smooth, creamy bokeh without harsh edges or "nervous" texture in the blur.
A Common Mistake: Groups at Wide Apertures
Shooting a group of people at f/1.8 almost guarantees some faces will be out of focus — anyone not in the exact same plane of focus as where you focused will be soft. For groups of two or more, use f/4 or smaller to ensure everyone is sharp.
How do I get a blurry background in my photos?
Use a wide aperture (f/1.8-f/2.8), a longer focal length (85mm or more), get close to your subject, and put distance between your subject and the background. The background blur (bokeh) increases with all four of these factors working together.
What aperture should I use for portraits?
For a single subject, f/1.8-f/2.8 gives beautiful background blur. For two people, f/2.8-f/4 is safer. For groups of three or more, f/4-f/5.6 ensures everyone is in focus. The exact aperture depends on how many people are in the shot and how much depth you need.
Why are some of my portrait photos out of focus?
The most common cause is a depth of field that is too shallow for the situation. At f/1.8, the in-focus zone can be just a few inches deep. If your subject moves slightly after you focus, or if you focused on the wrong part of the face, the eyes can fall outside the focus zone. Focus on the nearest eye and use a slightly narrower aperture if sharpness is inconsistent.
What is bokeh and how do I get it?
Bokeh is the Japanese word for the quality of blur in out-of-focus areas of a photo. To get pleasing bokeh, use a lens with a wide maximum aperture (f/1.8 or f/1.4), shoot at or near wide open, use a longer focal length, and put your subject close to the camera with the background far behind them.
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