How does aperture affect depth of field?

As you become more experienced in photography and venture into the technical details, you will learn how aperture (one of the components of the exposure triangle), affects not only the exposure of your images, but the depth of field as well...

How aperture affects depth of field

The relationship between aperture and depth of field can be likened to a delicate dance, where subtle adjustments yield impactful effects in your images.

As mentioned earlier, aperture, which is the opening in your camera lens that controls the amount of light entering the camera.

This means that the wider the aperture (a smaller f-stop value like f/1.8) then the more shallow the depth of field, and the more narrow the aperture (larger f-stop value like f/16) then the more narrow the depth of field.

Let's take a closer look at this inverse relationship.

Wide aperture and shallow depth of field

A wide aperture (represented by a smaller f-stop number like f/1.4 or f/2.8) creates a shallow depth of field.

In this scenario, only a small portion of your image—often the subject—remains sharply focused, while the background and foreground gently blend into a pleasing blur. Shallow depth of field is commonly used in portraiture, headshots, or product photography, as it allows the subject to stand out against a soft, bokeh-filled background, drawing the viewer's attention to the person or object of interest.

So for example, to capture this kind of image, I usually set my camera focus setting to single-point focus. You then put the focus point on my subject and make sure they are a good distance from the background. Once you take the photo you'll see that the subject is in focus and the background will be blurred.

Narrow aperture and deep depth of field

A narrow aperture (represented by a larger f-stop number like f/11 or f/16) results in a deep depth of field.

In this case, a larger portion of the scene—from foreground to background—appears in sharp focus. This technique is often employed in landscape photography or street photography, where the desire is to showcase intricate details from near to far, immersing the viewer in the breadth of the scenery.

Other factors that influence depth of field

While aperture is a key factor in controlling depth of field, it's essential to recognize that other elements also come into play, shaping the visual impact and focus within your photographs.

Understanding these additional factors empowers you to have greater control over depth of field and create images that align with your artistic vision.

Focal length

The focal length of your lens affects depth of field. Generally, shorter focal lengths (wider-angle lenses) tend to have a deeper depth of field, meaning a larger area appears in sharp focus. In contrast, longer focal lengths (telephoto lenses) tend to produce shallower depth of field, isolating the subject from the background.

Distance to subject

The distance between your camera and the subject also plays a role in depth of field. When you get closer to your subject, the depth of field becomes shallower, emphasizing the subject while blurring the background. Conversely, increasing the distance between your camera and the subject can result in a deeper depth of field, bringing more elements into focus.

Sensor size

The size of your camera's image sensor influences depth of field. Cameras with larger sensors, such as those found in full-frame or medium format cameras, tend to produce shallower depth of field compared to cameras with smaller sensors, such as those found in most entry-level DSLRs or smartphones.

In summary, when it comes to manipulating the depth of field without affecting the composition of your photo, making adjustments to the aperture remains the optimal choice. Its ability to selectively control focus and blur, coupled with its minimal impact on exposure, empowers you to shape the visual narrative of your image while keeping the intended composition intact.