Digital Photography Course: The Relationship Between Aperture and Depth of Field
Avatar photoNikki Zantop·
Introduction to Photography: A Free Beginner Course
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The Relationship Between Aperture and Depth of Field

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In this lesson we’re going to dive into Depth of Field! Depth of field is a measurement of how much of a scene is in focus and it can vary widely depending upon your camera’s aperture setting, which you’ll remember from the last lesson is changed by selecting a different f-stop. The “Field” in Depth of Field refers to the field of focus — how much of the scene is sharp. A shallow depth of field means that the area in focus is small, and a deep depth of field means that the area in focus is large.

Without going into too much detail on the physics of why the depth of field changes, when we use a wide aperture, sometimes referred to as a fast aperture, like f/1.4, only a small area of our scene will be sharp and in focus. With a smaller aperture like f/32, not only does less light enter our camera through the lens, but more of both the foreground and background of our shot will be in focus.

What are the Benefits of a Shallow Depth of Field?

A shallow depth of field can help to draw attention to the area of the photo that is in sharp focus. By shooting “wide open” using a fast aperture, distracting foreground and background elements can become soft blurs that no longer divert attention away from the subject of your photo.

Since the field of focus is very narrow when using a fast aperture setting, a shallow depth of field is often preferred for things like portrait photography. With the subject’s eyes in sharp focus, areas that are outside the field of focus appear softer, so wrinkles and other skin blemishes are less noticeable.

The farther away you are from your subject, the greater the depth of field will appear to be in your photo. For example, if you’re photographing a person standing a few meters away using a lens like the Canon 85mm f/1.8 lens with the aperture wide open, only a small part of their face will be within the depth of field, meaning that maybe only their eyes will be in sharp focus and the rest of their face will be softly blurred. When using a fast aperture and photographing people standing close to the camera, it’s important to focus on the eyes to ensure that they’re in sharp focus.

Using the same exposure settings and the same lens, if our subject walks a few more meters away from us, the perceived depth of field will increase and more of their face will be in sharp focus.

In this photo of a tree fern, the depth of field is very shallow and your eyes are drawn toward the area in sharp focus. With a smaller aperture that would come with using a higher f-stop like f/22, more of the forest background would be in focus instead of softly blurred. It’s obvious that a shallow depth of field improves this photo by eliminating the details in the cluttered background.

Digital Photography Course: The Relationship Between Aperture and Depth of Field

When is a Shallow Depth of Field not the Right Choice?

Many photographers love to shoot wide open using fast apertures that result in a very shallow depth of field. As you can see from the example above, this frequently improves a photo by keeping distracting elements outside of the field of focus. Using a shallow depth of field isn’t always ideal for every photography scenario though. Here are a few examples when a shallow depth of field might not be the right choice:

  • Photographing a Crowd or Group of People

    If you’re trying to photograph a large group of people and you want to be able to see the detail on each of their faces, you should use a smaller aperture setting to prevent a shallow depth of field. If you use a fast aperture setting like f/1.8 to photograph a nearby group of people and some of them are standing closer to you than others, you’ll end up with some faces in sharp focus and others out of focus. You can prevent this by increasing your depth of field by using an aperture setting like f/16.

  • Photographing Fast Action

    If you’re trying to photograph fast action sequences like a person running towards you or a butterfly dancing through the air, a shallow depth of field should be avoided. Because the field of focus is so narrow with a shallow depth of field, even a few inches can spell the difference between a shot with your subject perfectly in focus and one where your subject is just an out of focus blur. To increase your chances of capturing a moving subject in sharp focus, you can use a smaller aperture setting to increase your depth of field, bringing a wider area of the scene into focus.

  • Photographing Tiny Subjects

    Since it requires working in close proximity to a small subject like an insect, flower, or piece of jewelry, macro photography is a genre that typically requires a deeper depth of field, in order to get the entire subject in sharp focus. Generally, macro photographers try to find an appropriate aperture that allows them to capture their entire foreground subject in crisp focus, while still rendering a soft background that won’t distract viewers. Occasionally, a shallow depth of field might be used in macro photography to highlight the detail on a small portion of the subject, like a single water droplet on a leaf, but exercise caution when using a shallow depth of field while shooting macro photography — even a small movement of your camera’s position can result in an out of focus image.

  • Photographing Text or Other Details on an Angle

    Unless you’re photographing something like a sign, book cover, or painting head on, shooting from an angle with a shallow depth of field will result in only your specific point of focus being sharp. Sometimes this can be used creatively if you don’t need to be able to clearly read or see everything in the scene, but if capturing all the details is important, you’re better off using a higher f-stop to produce a deeper depth of field with more of the scene in focus.

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