Chapter 7: Depth of Field

“Depth of field” (DOF) is the optical property of a photographic lens that determines the degree of sharpness between objects close to the camera and those farther away. When both distances, near and far, are sharp the DOF is said to be “long” or “deep.” When only the point of critical focus in the foreground is sharp with the background out of focus, the DOF is “narrow” or “shallow.”

There are mathematical considerations that affect the DOF, but in practice, the features that concern the photographer are a) the lens’s aperture or f-stop, b) the focal length of the lens and c) the camera-to-subject distance. Each is an independent variable, but they combine to produce the DOF. When photographing purposefully, it’s always a consideration.

APPLICATION AND TECHNIQUE

Aperture

Long depth of field, where objects both near and far are sharp, spreads the viewer’s attention over the entire image. It encourages the eye to explore all the details within the frame. When a lens is “stopped down,” admitting little light, the f-stop numbers hover around f16, f22, f32. The higher the number, the longer the depth of field. In this range, when “critically focusing” on a near subject, the background will also be sharp.

Narrow or short depth of field compels the eye to stay focused on the dynamic center, the point of critical focus in the foreground. The more open the lens aperture, the more light gets through to the recording medium—film or camera card. These aperture numbers hover around f2.8, f 3.5, f4. The lower the number, the narrower the DOF. In this range, when critically focusing on a subject near the camera, the background will be out of focus.

Focal Length

Fountain Square, Cincinnati, Ohio

The focal length of a lens determines the area of coverage that a camera “sees.” Here, a “wide angle” lens includes the sky, plaza and fountain.

A “medium” or “normal” focal length lens shows some sky, but the buildings in the background are prominent.

“The Genius of Water” atop the Tyler Davidson Fountain

A “telephoto” lens lets the photographer get a closer view without physically moving close to the subject. Here, the optics excludes everything except the figure at the top of the fountain and what’s behind it. The camera’s aperture was fairly wide open, rendering the building slightly out of focus.

A very wide angle lens, even with the aperture wide open, will likely render both the foreground and background as sharp. Conversely, the aperture of a telephoto lens has to be “stopped down” considerably in order to keep the background sharp. This is one of the reasons why professionals carry many lenses—or a zoom lens where the focal length can be varied from wide to telephoto.

Camera-to-Subject Distance

As a camera is brought closer to the primary subject, the foreground and background in the frame tend to go out of focus, necessitating a smaller aperture to keep them sharp.

As the camera-to-subject distance is increased, objects both near and far will be more in focus. A camera moving closer to a subject is equivalent to a person moving closer. It’s why movie directors prefer cinematographers to use single focal length (“prime”) lenses rather than a zoom lens. They want the viewer to feel like they are in the subject’s personal space.

PERSONAL AND SOCIAL REFLECTION

Our eyes continuously shift from wide to medium to closeup perspectives in an instant. Cameras have a single and objective “eye.” And they only record in two dimensions. We see in three dimensions and our perception is subjective—we make sense of what’s in front of us, real or imagined. This observation is so obvious, it hides the significance of perception as a process of thoughts that make meaning, which in turn drive action.

If we consider a “field” as a domain of thought, of consciousness, the question arises: What is my personal depth of field? How deep does my thinking go? Most of the time, when we’re not focused on everyday concerns, where do we place our focus? Daily, like a zoom lens, we shift between close-in, self-oriented and short-term matters, and broader, more other-directed and long-term thinking.

As an organism starts to develop it begins to resonate to a certain field, and the more the organism follows that particular path the more it becomes habituated and goes on developing within that field to its final form.

Judy Cannato, American Catholic author, retreat facilitator, and spiritual director

Becoming habituated to a particular field of thought is like viewing the world solely through a “normal” lens. But in everyday living, our depth of thought shifts continuously. Looked at analogously, a camera’s aperture controls the amount of light that reaches the recording medium. How much light of awareness am I letting in by exposing myself to diverse perspectives, higher (more complex) consciousness, creative and inspirational sources? What is currently the depth of my thought-field? What’s mostly on my mind?

Consider also the focal length of a lens that determines the extent of subject coverage. Am I taking advantage of opportunities to change lenses (perspective), to empathize, walk in other people’s shoes, expand my field of thinking by observing people and circumstances close up, broadly, and farther away in order to supplement my “normal,” routinized ways of thinking? And with regard to camera-to-subject distance, am I venturing out, exploring other fields of thought, ideas and values? Of course, there are no right or wrong, better or worse, responses to these questions, but they recommend wider and deeper perceptions when considering where we are in the unfolding process of trying to live our lives more authentically and productively.

New perceptions and insights fill us. The five senses no longer limit our experiences. We are learning to distinguish love from fear within ourselves and to choose love no matter what happens inside us or what happens outside. This is authentic power. We are seeing for the first time that the love and fear in the world are the love and fear in us. Therefore, only by changing ourselves can we change the world. All this is only the beginning.

Gary Zukav, author Universal Human

On the subject of “consciousness,” my friend Glenn Geffcken authors a blog, The Deeper Side of Things. I highly recommend it.

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My other sites:

Substack: Poetry and insights relating to creation and Creator

David L. Smith Photography Portfolio.com

Ancient Maya Cultural Traits.com: Weekly blog featuring the traits that made this civilization unique