Aperture & Depth of Field

Moving on with our photo class series, we come to the next point of our exposure triangle: aperture. Aperture can, at first, be a little tricky to wrap one’s head around but when you compare it to an eye, it becomes clearer. A camera’s aperture is dictated by an iris in the lens. Much like your eye, this iris can be opened and closed to regulate the amount of light passing through the lens. Using this adjustment you can either darken or lighten your resulting image.

Aperture has a secondary impact on your image. As you open or close this iris your change the depth of your image that is in focus. This is what is know as depth of field and is how portrait photographers soften the backgrounds of their models or how landscape photographers focus an incredible range of distance into one photograph. Selecting a low aperture opens the iris wider and shortens the focus range, what is known as a shallow depth of field. While a higher aperture increases that range.

In this example I used a very low aperture, f/1.8, and focused on the leaf in the middle. By using such a wide open aperture I was able to blur both the foreground and background leaving the leaf sharply in focus. This technique helps to maintain the viewers focus on the subject by actively taking the rest of the image out of focus.

In this example I used a much higher aperture, f16, to capture in-focus detail from the ripples in the water in the foreground all the way to the clouds and far off shoreline. This allows the viewer to gaze through the image and explore the details of the expansive scene.

For a deeper dive into aperture and the f-stop scale watch the video below. Additionally, I share a mental trick to remembering the relationship between aperture size and depth of field.