Depth of Field in Photography: The Art of the Unsharp Image

There’s no shortage of online resources about depth of field, but they tend to be dry and mathematical (and in some cases, inaccurate or plain wrong). This article is the first of a two-part series about depth of field. Part 1 is about artistic choices, while Part 2 will be about technical choices: how factors like aperture, focal length, subject distance and sensor size affect depth of field. You can think of Part 1 as the Why, and Part 2 as the How.

It’s all too easy to become enamored by fast lenses and large sensors – a quest for the shallowest depth of field, the creamiest bokeh. But it’s worth taking a beat to think about why we make certain choices. Why might we choose a shallow (or deep) depth of field? How do we choose what is in focus, and what is not? And what impact do our choices have on the photograph, and on the viewer? Only then does it make sense to talk about how to achieve the desired depth of field, which we’ll cover in Part 2.

What is depth of field?

“I often think that photography’s greatest contribution to the graphic arts is the unsharp image,” wrote Harold Merklinger in The Ins and Outs of Focus.

Painters traditionally rendered all parts of the image “in focus”. For example, in the still-life below (left) – La Merienda (The Afternoon Meal) by 18th-century Spanish painter Luis Egidio Meléndez – the fruit in the foreground and the trees in the background are both rendered more or less sharply. In Kano Tsunenobu’s 17th-century silk painting (below, right), the mountains are drawn with lower contrast and detail to suggest distance and haze. But they are not blurry in the same way as they would be if they were “out of focus”, as we are used to seeing in photographs.

In many photographs, on the other hand, some parts of the image are in focus and sharp, while others are out of focus and blurry. What’s more, this is something which the photographer can control – up to a point. The depth of field, which affects how much of an image is in focus, can therefore be a conscious creative choice.

In the photo of the typewriter below, I focused on the G key, but F and H are also in focus. On a computer screen, D and J look unsharp, while A and L are visibly blurry even on a phone screen. We use the term “depth of field” to refer to the in-focus zone: the range of distance from the camera where objects are in acceptably sharp focus.

In the diagram above, the orange line is the plane of focus, and the blue zone is the depth of field. Beyond the near and far limits of that zone, objects get progressively blurrier.

If a lens is focused at, say, 5 meters, technically, sharp focus is only achieved at exactly 5 meters from the film (or sensor) plane. However, objects which are somewhat closer or further away will also look sharp enough that for practical purposes, and at a reasonable print or display size, they also seem to be in focus. This range – which depends on a number of factors such as aperture, focal length and distance to subject – is called the depth of field.

Technically, a lens has only one infinitesimally thin plane of perfect focus, where a point in the real world will be imaged as a point on the sensor. (That’s in theory; in practice, no lens is optically perfect.) The plane of focus is typically parallel to the film or sensor, i.e. perpendicular to the direction we are pointing the camera. We can use view camera movements or tilt-shift lenses to swivel the plane of focus, but I’ll not get into that here.

The most common and straightforward way to control depth of field is via the aperture. Other things being equal, a wide aperture, say f/1.4, produces shallow depth of field, while a small aperture, like f/16, produces deep depth of field. Other factors play a part too, which we will cover in more detail in Part 2.

Below are two images which show the difference between shallow and deep depth of field. The depth of field may be shallow, like the first image, where only the scroll and pegs of the cello are in focus. Or it may be deep – like the second image, where focus extends from the vintage posters in the foreground to the neon sign in the back.

Imager showing shallow DoF.

Imager showing deep DoF.

Think Deeper

Why do focus and depth of field matter? There are (at least) two ways to think about it: information and aesthetic.

Choosing where to focus, and how deep the focus should be, is one way that photographers can “interpret” a real-life three-dimensional scene into the two-dimensional plane of a photograph.

A photograph can contain lots of “information”, and not all of it is relevant. Some details may even be distracting or otherwise undesirable. With a shallow depth of field, we can isolate certain parts of the image which we want to draw the viewer’s attention to. The rest may be rendered somewhat out of focus (blurry but still recognizable) or completely out of focus.

The photo of my dancer friend was taken at an abandoned housing estate. A shallow depth of field relegates the (rather messy) background to a pleasing blur, but elements of it are still recognizable – apartment blocks, water pipes, trees. With the dragonfly, on the other hand, the background is a formless blur. The depth of field is so shallow that even the wingtips are out of focus.

Focus creates a visual hierarchy: our eyes are naturally drawn to those parts of an image that are sharp. As Stephen Shore put it in The Nature of Photographs, “there is a gravitation of attention to the plane of focus.” It’s as if the photographer is reaching across time and space, gently guiding the viewer’s gaze.

Sometimes, by focusing on something other than what the viewer might expect, we can subvert their expectations and draw them in. The two photos below are from a shoot I did for my friend Jialing. Her grandma had just died, and the apartment where she lived, and where Jialing spent much of her childhood, was being sold off.

As Jialing moved through the flat, tracing the furniture with her fingertips, reflecting on her childhood memories and letting her emotions flow, I often chose to focus on the objects in the flat, using a shallow depth of field to suggest but also partially obscure her presence. The effect is to afford her a measure of privacy, and perhaps also remind us of the tangibility of physical objects and the ephemerality of human existence and memory.

Shallow depth of field is not the only way to isolate a subject. Subject isolation can also be achieved with other techniques such as lighting (in the the nightclub photo below, on-camera flash illuminates the singer, leaving the background in relative darkness), motion blur (the dance photo was a ¼-sec exposure, with one dancer standing still while the others moved around), and panning (tracking a moving subject to keep it sharp while blurring the background).

Should we always aim to isolate the subject? Not necessarily. Irrelevant details can be distracting, but more detail is not always a bad thing – especially if the photograph is composed in a way that the details are harmonious and coherent. Sometimes, we want more detail – for example, to tell a story, or to show more of the subject and their environment. A deep-focus photograph can be visually richer, providing the viewer with more information to explore, examine and parse. Such images can have more enduring appeal than a single, sharply isolated subject against a sea of blur.

In a way, photos with greater depth of field are closer to how we experience the world with our eyes. There are more layers – layers in space as well as layers of meaning. John Kennerdell argues that “the richest photos – the ones we return to again and again, seeing more each time – most often work in layers. They show more rather than less, taking in the full spatial depth of our world rather than just one razor-thin slice of it.”

In a comment on Kennerdell’s article, a reader made a comment which I thought was really perceptive and worth quoting at length. “I like a good super-shallow DOF image as much as anyone, but the experience for me often feels like tasting a piece of candy – a sense of instant gratification that lasts only as long as I’m looking at the photo. I never feel a desire to go back and look at such photos again and again, nor do I learn much from them. They are often beautiful to look at, but rarely reveal anything beyond the first (often only) layer.” 

Indeed, most famous photos that I can think of have medium to deep depth of field. Even when it comes to portraits, masters of the art like Yousuf Karsh and Annie Leibovitz typically use deeper focus than most amateur photographers would. 

In multi-layered photos like Swimming Pool by Martine Franck, Ramsgate, Kent by Martin Parr, Vuokkiniemi by Pentti Sammallahti, The World from My Front Porch by Larry Towell, we can let our eyes wander all over the scene, feasting our eyes on the different elements and their relationships in space. As this StudioBinder video puts it, “With everything in focus, it is our own eyes which do the editing.” Deep-focus photos are arguably more collaborative, “trusting” the viewer, whereas in a shallow-focus image, the photographer tells us precisely where to look.

In all three photos below, I stopped down to varying degrees (i.e. used a smaller aperture, like f/5.6).

The market scene above had multiple planes of action – the boxes and bicycle (foreground), the three men sitting on the left (middle-distance), and the men carrying boxes (varying distances from the camera). A smaller aperture helped me capture that depth and bustling activity.

In the aerial hoop photo, we wanted a sharp background for a more prosaic reason: the studio was letting us use the space for free, and wanted their logo to be clearly visible.

The dance photo was shot at Gardens by the Bay in Singapore, and we wanted the background to be sharp – to give a sense of place. The way I see it, there’s little point in doing an on-location shoot if the background is blurry and barely recognizable; we may as well shoot in a studio.

Aesthetics

Shallow depth of field is often associated with a soft and dreamy look, seen in the work of photographers such as Rinko Kawauchi, Sally Mann and the Pictorialists. Even if you’re among those who decry the current tendency – especially among portrait photographers – to shoot all photos at the widest possible aperture, it’s hard to deny that a smoothly blurred background just looks pleasing to the eye.

An out-of-focus background can function as negative space. It gives the main subject room to breathe, and gives our eyes somewhere to rest.

Blur can even be a subject in its own right. Some photographs are more about evoking a feeling – dreamy, fuzzy, ambiguous – and less about capturing a sharply delineated subject.

Wide apertures, and the resultant shallow depth of field, are especially popular for portraits. This is partly because blurry backgrounds contribute to an overall softer feel.

Moreover, when you shoot wide open, it’s not just the out-of-focus areas which are softer, but the in-focus parts of the image too. This latter effect is not due to shallower depth of field, but due to optical “flaws” in the lens, such as spherical aberration, which are more pronounced at wider apertures. These aberrations help smooth out skin blemishes, creating more pleasing portraits than you would get with a clinically sharp lens that picks out every zit and wrinkle.

On the other hand, depending on your style and subject matter, a soft and dreamy look may not be what you want. This, too, is an aesthetic choice – just a different aesthetic. In California in the 1930s, a few like-minded photographers, including Ansel Adams and Edward Weston, founded Group f/64. f/64 is of course a very small aperture, providing vast depth of field. Unless you’re into large-format photography, your lens probably doesn’t even have an f/64 setting.

The group’s manifesto said that their name “is derived from a diaphragm number of the photographic lens. It signifies to a large extent the qualities of clearness and definition of the photographic image which is an important element in the work of members of this Group.”

In contrast to the aforementioned Pictorialists, who favored a soft and dreamy aesthetic, Group f/64 – as Mary Street Alinder relates – mandated “sharper lenses and closing down the aperture to extend the depth of focus. Sharpness became the defining logo of modernist style.”

Group f/64 embraced small apertures in their bid for greater realism and objectivity. But deep depth of field also characterises – and contributes to – the edgy, surreal aesthetic of photographers like Ren Hang and Daido Moriyama, the gritty street photography of Eskenazi, Winogrand and Weegee, and the precise, self-conscious formalism of Rineke Dijkstra and the Bechers.

Deep depth of field is often used in architecture photography, and the two examples below, shot in Helsinki, are no exception. Portraits, which often make use of shallow depth of field, can also benefit from deep DoF. In the picture of my actor friend (also included below), we were not going for the soft and mellow look. Shot late at night in a bamboo grove as she improvised an intense scene, the image is meant to be raw and visceral. Hard light and high contrast contribute to the effect, as does the deep depth of field which picks out every detail with unflinching clarity.

Free will

In a previous article, I wrote about my experience in the summer of 2011, when I went from shooting a small-sensor digital to a 35mm film camera. What stood out for me was not just the superior tones and dynamic range, but also the shallow depth of field that I could get with the larger “sensor size” of 35mm film, and my Minolta 50mm f/1.8 lens.

In Part 2 of this series, I will say more about the relationship between depth of field and sensor size. For now, suffice to say that like many photographers when they first step up to a bigger sensor, I immediately went through a phase of shooting everything at the widest possible aperture, luxuriating in the “large-sensor look”.

I’m pretty sure that this is one reason why shallow focus is so popular, or even overused, among amateur photographers. A razor-thin depth of field sends a subliminal signal that the picture was made with a “real camera”, not a mere iPhone or point-and-shoot.

To own, say, a full-frame camera and fast lens but still use it stopped down might almost feel like a waste. Unlike vintage lenses, most modern lenses are reasonably sharp at all apertures. And shallow depth of field almost invariably looks pleasing, and gets likes on social media.

It’s also an easy mental shortcut. If you always shoot wide open, you have one less thing to think about. I still fall into this trap sometimes. Both these photos were shot at f/1.4, and in hindsight, I wish I had used a smaller aperture to capture more detail on the Chinese opera stage, and on the Taoist figurine.

I’m not suggesting that we should always stop down, any more than I’m saying we should always shoot wide open. Shallow and deep depth of field both have their place. Rather, the message of this article – which I myself sometimes fail to heed, as the last two examples show – is to be more intentional in our choices.

A default rule – like always shooting wide open, or f/8 and be there – can be convenient, but we shouldn’t let it make us lazy. Photography is a language with a generous vocabulary, and depth of field is part of it. It would be a shame to unthinkingly limit ourselves to either shallow or deep focus; we should fully explore that vocabulary, and the kinds of stories we can tell. We are humans with free will, adjustable aperture and interchangeable lenses. In Part 2 of this series, I will talk about how we can use these to control depth of field, and to pursue – and perhaps someday realize – our creative vision. ∎

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