Depth of Field

When you’re shooting an image, you’re also telling a story to the viewer. It’s your job to tell them where they should be looking, and directing their attention to the photo’s key elements. There are a number of tools you can use to tell the “story” of your image. One of those tools is depth of field (dof). Depth of field (DoF) is one of the most important concepts in photography. Understanding what DoF is, and knowing what factors affect it, are things all photographers should master.

Depth of field is the distance between the closest and farthest objects in a photo that appears acceptably sharp. Now your camera can only focus sharply at one point. But the transition from sharp to unsharp is gradual, and the term ‘acceptably sharp’ is a loose one! Without getting too technical, how you will be viewing the image, and at what size you will be looking at it are factors that contribute to how acceptably sharp an image is. It also depends on how good your vision is!

Determining Depth of Field

Many DSLRs have a depth of field preview button. If you press this button while you look through the viewfinder, the camera will stop down the lens, and you will see how the actual image will look. However, at small apertures, the viewfinder will get very dark, and it will be hard to see the preview!

Live view can also be used on some camera models to preview how the DoF will look. Check your instruction manual to see if your DSLR can do this.

Mirrorless shooters potentially have an advantage over DSLR shooters because what they see through the digital viewfinder, or on the LCD is how the photo will typically look.

Factors Affecting Depth of Field

A few different factors affect depth of field in digital photography, regardless of whether you’re using a DSLR camera or a smartphone. These factors are: focal length, aperture, camera-subject distance, and sensor size.

As you come to understand these factors, and the camera settings that control them, you’ll be able to manipulate this photographic effect to increase depth of field, improve image quality, toggle between sharp focus and soft focus, and generally bring more variety to your photographic portfolio.

Focal Length- The focal length of a camera lens contributes to depth of field: a longer focal length corresponds to a shallower depth of field and a shorter focal length corresponding to a longer depth of field. Generally, a wide angle lens has a deeper depth of field than telephoto lenses, which can offer an impressive focus distance but are sometimes more limited in options. A zoom lens, on the other hand, offers multiple focus distances, and can thus perform a wide array of photographic tasks.

Aperture- Aperture is the opening in your lens that lets light pass through to the sensor. Large apertures, which correlate to small f-stop numbers, produce a very shallow depth of field. On the other hand, small apertures, or large f-stop numbers, produce images with a large depth of field. 

Camera-Subject Distance- Another important factor affecting depth of field is the distance between the camera and the subject. The shorter that distance, the smaller the depth of field. Have you ever tried to take a close-up shot of a flower or insect, but can’t get the entire subject in focus, even with a small aperture? This is because the closer you are to your subject, the shallower the DoF.

Sensor Size- Camera sensor size is the final important factor in depth of field. If the other factors are the same—aperture, focal length, camera-subject distance—a larger sensor will have a shallower depth of field. In general, cameras with smaller sensors have larger depths of field. Sensor sizes vary between models of cameras; cameras with full-frame sensors have a lot of surface area whereas cameras with the newer APS-C sensors have smaller surface areas. Sensor size is an important factor when it comes to selecting a camera to use, since it directly impacts the quality of your photos (and thus, your creative expression).

Deep vs narrow depth of field

Images that are sharp from front to back are said to have a deep depth of field. A deep depth of field is popular in landscape photography, where you often want to show every little detail from the scene.

On the other hand, some images have very small zones of focus, known as shallow depth of field. Shallow depth of field photos are immediately noticeable because the subject will remain tack-sharp, while the background renders as a smooth, creamy blur. This effect is especially popular in portraiture; photographers use it to draw attention to their subject while preventing background distractions.

How to Decrease Depth of Field in Your Photos

Let’s say that you want to create a shallow depth-of-field effect in your photos, where you single out one aspect of the photo to be in focus. Typically this would be your foreground subject, with the background somewhat blurred. To create a shallow depth of field on a DSLR, you will want to:

1. Use a wider aperture. The more light you let in, the easier it is to create that shallow depth of field.
2. Use a telephoto lens to photograph an object that is relatively close. The increased focal length (larger f number) of a telephoto lens presents more opportunities to a photographer. While some amateurs believe that such lenses are only used to photograph distant objects with a uniformly sharp focus, they can actually be used to create a fantastic shallow depth effect in close-up portraits.

Physically get closer to your subject. If you don’t own a telephoto lens, that’s no problem. By getting physically closer to the object you are photographing, you can enjoy all the advantages that a longer lens would otherwise provide—including the ability to focus in a way that produces a shallow depth of field.