Bokeh is a word that carries a lot of weight in modern photography circles and can, surprisingly, breed heated conversations, but what does it really mean and how does it apply to portrait photography? As an introduction, consider the word—which is derived from the Japanese term for “blur” or “haze”—to mean the aesthetic quality of the out-of-focus parts of an image surrounding an in-focus subject. It is not simply something not in focus, it is a product of shallow depth of field and can be quite beautiful on its own, but also lends to the beauty and effectiveness of the overall composition. Bokeh is most often noticed when points of light, either direct or reflected, are blurred and create a dappling effect in the background of an image, but bokeh is more than just soft spots of light, and the quality of bokeh is a product not only of light and photography technique, but of the type and quality of the lens one uses.
Before we can discuss bokeh, it’s important to understand the idea of depth of focus or, as it’s more commonly referred to, depth of field. When we focus on a subject within our frame we can control how much of the overall image—foreground to background—is in focus. In a wide depth-of-field image, everything is in focus, from the items in the foreground to the primary person or subject of the photo, to the background. Think, for example, of a well-lit image of a person in front of distant mountains, in which the person and the mountains remain in focus. Shallow depth-of-field focusing is when one aspect of the image is in focus and the rest is slightly blurred. In portraiture, the aspect in focus is usually the face of the subject or even just the eyes, while the rest of the frame is in progressively softer focus.
Depth of Field in Portraiture
As an introduction to general portraiture, there are two ways to render shallow depth of field. First, adjust the aperture on your lens to a wider setting, ideally as open as possible. Lens apertures are measured in “f-stops,” with a wider opening having a lower f-number, such as f/1.8 or f/2. Conversely, smaller apertures are noted as f/22 or even higher. Every lens has a different set of f-numbers, and “fast lenses” are those better suited to create shallow depth of field. Setting a portrait lens, which generally has a focal length between 70mm to 135mm, to a wide-open aperture is a pretty straightforward way to render shallow depth of field with nearby subjects and thus create bokeh in the out-of-focus areas.
A second way to create bokeh is to use a longer focal length lens, such as a telephoto. A telephoto lens not only suits photographing distant objects, it also condenses the elements within a frame to appear closer to each other. With focus on the primary subject in the foreground, items in the background will seem much closer to the subject but remain out of focus, creating a natural background blur. Again, think of a person in front of a mountain. If you are using a telephoto lens, you will need to distance yourself from your subject to achieve focus and to fit them comfortably in the frame, but the mountains will appear as if just behind the subject’s head, nicely out of focus. The quality of this out-of-focus area is bokeh. Experts can then argue if it is “pleasing,” “smooth,” “creamy,” or simply “good” bokeh.
For a bit more information on depth of field, in general, take a look at Todd Vorenkamp’s three-part series on the subject.
Bokeh in Portraiture
Bokeh is an effective tool in portrait photography. With a blurred background or even blurred items in the foreground on the side of a frame, the viewer’s attention will be directed to the in-focus aspects of the image, normally the face and eyes. Using extremely shallow depth of field, photographers can place focus on just the eyes (or even on one eye) while the other facial features, the hair, and anything else in the foreground or background will be progressively out of focus. This is a very common practice in portraiture, but what exactly is “good” bokeh and how is it created?
The concept of bokeh is, again, debated fiercely in some photography circles. Good bokeh is often described in subjective terms, but pleasing bokeh is just that—pleasing to the viewer. It adds an element of beauty and does not distract from the subject or overall composition. More specifically, the edges of its out-of-focus light are not harsh or overly sharp and, if circles of blurred light are created in the image, they are uniformly illuminated and, hopefully, as round as possible. How does “good” bokeh come about in portraiture? In addition to the previous techniques mentioned to create shallow depth of field, the type of bokeh is determined by the lens used. The shape of the diaphragm inside the lens, as well as the lens’s optical design and the glass itself, are all key determinants of bokeh quality.
Diaphragm and Aperture Design
The aperture of a lens is the adjustable hole through which light passes and its size and even shape can be controlled. The aperture in most modern lenses is created by an iris diaphragm, which uses a number of small blades that contract and open to vary the size of the aperture. The shape of the aperture, also determined by these blades coming together, whether a true round opening or an opening with polygonal dimensions, determines the shape of bokeh. This form of bokeh, perhaps the easiest to recognize, is created when individual lights, spectral highlights, or strong points of reflected light, like reflections from individual leaves or even hair, are in the frame but out of focus. The shape of the aperture will translate to the shape of these out-of-focus highlights, with a round aperture producing round highlights, a hexagonal aperture producing hexagonal highlights, and so on.
In general, when an aperture is wide open, the shape is closest to circular. When setting your aperture, consider this if you want noticeably circular bokeh. Lens makers, recognizing the benefits of a pleasing circular bokeh, have created lenses with a high number of individual diaphragm blades or blades with curved edges to make the aperture more closely approximate a circle when set to narrower apertures.
But bokeh is not only about circular highlights; the concept informs all aspects of the out-of-focus spaces within a frame. Some lenses are noted for creating a swirly bokeh and others for uniform and smooth characteristics. When using backdrops in portraiture, the bokeh created by the lens might overlap with the mottled design of a quality backdrop to wonderful effect. Those who know gear can speak on various lenses, new and vintage, that are known for particularly pleasing bokeh. Telephoto mirror (catadioptric) lenses are known for their “donut”-shaped bokeh because their internal mirror blocks the center of the aperture opening. Companies like DIYP create insertable aperture discs with cutouts of hearts, stars, or smiley faces that will create bokeh in those shapes.
Spherical Aberration
In addition to aperture shape, the optical design of a lens and its ability to correct aberration are factors determining the characteristics of a lens’s bokeh. If spherical aberration is not corrected, bokeh that is brighter on its edges or, conversely, brighter near its center, are the outcomes. In general, quality bokeh is created by quality optics, but not only—it is a very subjective realm. In the past twenty years, as bokeh has become a more integral part of discerning photography, overall advances in lens making have created more affordable wide-aperture portrait lenses and aberration correction is a common feature for modern lenses, so the technology is within financial reach. Also, advances in digital and computational photography enable bokeh to be artificially generated and added to an image. Conversely, older, more traditional lens designs are also known for the quality of bokeh they produce, like, say, a Petzval-inspired lens, which produces very distinct and swirly bokeh.
Conclusion
So, as a portrait photographer, how do you use the tools and techniques at your disposal to create powerful portraits with pleasing bokeh? Understanding the relationship between aperture, focal length, and depth of field is fundamental. Use fast-aperture portrait lenses and use them at their maximum aperture. Also, if using a long telephoto lens, move as close to your subject as possible and increase the distance between subject and background. When shooting on location, be sure to know your background; know if it has artificial light sources that will appear in the frame and how and when it is illuminated by natural light. Placement of bokeh in your image should be controlled to accentuate your primary subject best. When in a studio, try a neutral backdrop and utilize backlight or hair lights to create reflections and points of light around your subject. These are rules of thumb, but the key to understanding any photo technique, especially one as idiosyncratic as bokeh, is to experiment.
In the Comments section, below, let us know your thoughts on bokeh and any tips you may have for creating pleasing out-of-focus highlights in your images.