Understanding Depth of Field

by Mastin Labs

As a landscape photographer, you capture sweeping images of oceans capes, mountainsides, skylines, and wilderness. Your photos thrive on dramatic details viewed from close up and far away: Trees, birds, blades of grass are brought into focus to set the perfect stage.

As a portrait photographer, you’re most concerned with photographing the unique, defining features of your subject; the bright sparkle in an eye, the freckles on a face, the tiny wrinkle in a chin. Images like this aren’t possible without understanding how to use depth of field (also known as focus range) to bring certain parts of your image into focus and blur out what’s less important.

What is Filed of Depth?

Simply explained, the term 'depth of field' refers to the area of an image that appears to be in focus. As the distance from the focal point increases, the focus gradually decreases until it appears to be out of focus. In any image, there’s a point of absolute focus and a corresponding region of the image surrounding the subject that appears to be in focus.

If an image has a deep depth of field, it means its area of perceived focus is a broader and deeper portion of the image. If an image has a shallow depth of field, it means its area of perceived focus is limited to a narrower range.

Understanding depth of field is important and can greatly influence your photography; it helps distinguish the foreground from the background to create a focal point that draws the eye and tells it where to look. Knowing how to control depth of field gives you the opportunity to choose how much of (and what parts of) your image you want to bring into focus.

Referring back to the example in the introduction, landscape photographers typically want to capture a deep depth of field, where most of the image is in focus, from the foreground to the background. Portrait photographers typically want a shallow depth of field, where a smaller plane of detail in an image is sharpened, and any distractions in the background that may take away from the detail of the face are blurred.

Depth of field is not equally distributed around the focal point. It is typically distributed unequally, with about 1/3 of the total field of focus lying in front of the subject, and two-thirds of focus lying behind the subject.

There are three main factors that lay a role in creating depth of field. They are:

Aperture (F-Stop)
Distance
Focal length

We will discuss how you can control these three factors to create your desired depth of field in your images.

“Knowing how to control depth of field gives you the opportunity to choose how much of (and what parts of) your image you want to bring into focus.” - Mastin Labs

Aperture

To gain a top-level understanding of how you can achieve shallow or deep depth of field by controlling aperture, here is a quick overview of aperture and its related elements: F-stop, shutter speed, and depth of field.

If you shoot in anything other than a totally controlled environment, you have to know how to adjust your camera for the changing light. Aperture is the part of the lens that controls the amount of light passing through to the camera’s sensor, and its one of the simplest ways to control the depth of field. You can change the access of light by widening and narrowing the diameter of the opening through which light enters the camera.

When you increase aperture, the diameter widens, the lens lets more light in.
When you decrease aperture, the diameter narrows, the lens lets less light in.

Aperture corresponds with the f-stop numbers on your camera, lower f-stop numbers mean higher aperture.

Shallow depth of field

Set your f-stop to a low number (for example, f/2.8). This will widen your aperture, and you will allow a lot of light into the lens. To compensate for the flood of light you need to shoot faster by adjusting your shutter speed. Your resulting depth of field will be shallow.

Low f-stop number (large aperture) – Fast shutter speed= Shallow depth of field.

Deep depth of field

Set your f stop to a high number (for example, f/11). This will narrow your aperture, and you will let very little light into the lens. To compensate and to avoid having an underexposed image, you will need to shoot slower by adjusting your shutter speed. Your resulting depth of field will be deep.

Large f stop number (small aperture) – slow shutter speed= Deep depth of field.

Aperture is not infinite; all lenses have their limits, which are clearly defined by the manufacturer. Manufacturers state a minimum and maximum range that the lens can be shot.

Distance and Focal Length

The aperture, as discussed above, is just one element of depth of field. The distance from you to your subject can change your perceived depth of field.

You can adjust your distance in two different ways:

Moving closer or farther away from your subject
Use a longer or shorter focal length.

Deep depth of field

Wider aperture, when applied at a distance (physically, or with a shorter lens) from the focal point, results in an apparent deeper depth of field than it does when it’s applied to a closer subject.

The farther you are from your subject, the deeper your perceived depth of field.

Shallow depth of field

Inversely, when you shoot the same subject at closer distance (physically, or with a closer focal length), you’ll notice a shallower depth of field.

The closer you are to your subject, the shallower your perceived depth of field.

Without getting too technical, it’s important to note that this apparent change in depth of field when applied at a closer or farther distance has everything to do with the portion of the frame that the subject fills. With magnified shots, less of the background is represented in the shot, and the blurred background is magnified, making the image appear to have a shallower depth of field. The inverse effect happens when an image is taken at a farther distance.

While distance plays a large role in depth of field, knowing how to adjust the f-stop to compensate for distance is often a much more convenient way to achieve your desired depth of field. This is especially true in landscape photography, where moving farther from a subject in any significant way is much more difficult than it is in close-up photography.

By Bisual Studio

When to Use Deep Depth of Field

Deep depth of field is a great way to bring out detail in a large portion of the frame. Deep depth of field is commonly used in landscape photography to capture elements and textures in the majority of the frame throughout many vertical planes. To capture fine detail and deep depth of field, you should use a wide-angle lens to shoot at a distance and set your f stop at a high number for a small aperture.

To shoot a deep depth of field:

Shorten your focal length (use a wide angle lens)
Increase distance from your subject.
Set your f stop to a higher number for a lower aperture.

When to use shallow depth of field

Shallow depth of field is a great way to bring focus to a specific subject to separate it from its background. Shallow depth of field is commonly used in portrait photography and food photography. It is also great for action photography, such as sports and wildlife photography, because it separates the subject from their chaotic background and allows you to shoot with a quick shutter speed to capture crisp detail in action.

To shoot for shallow depth of field:

Increase your focal length (use a telephoto lens).
Shoot close to your subject.
Set your f-stop to a low number for a larger aperture.

By following these tips outlined above, you should now be able to generally control your depth of field to take the images you want. The more you practice and experiment with aperture, distance, and focal length, the more you’ll be able to fine-tune depth of field in your images to enhance your individual photography style.

Learning to control depth of field will help you bring focus to the most important parts of your images and will greatly improve the technical and aesthetic quality of your photos.