Text and Photos by Chuck Place
Back in the day when my students actually shot on location together, pre-virus, discussions on depth of field were a continual topic. This was partly because some my students had just moved away from full camera automation, the dreaded “P” setting for Program, and had tasked themselves with taking control of their camera. Using the class recommended “Av” or “A” setting, Aperture Priority, photographers have to manually set the aperture, or f-stop, and the camera picks the shutter speed for the exposure. The “A” setting not only controls exposure but also depth of field and that is where the confusion often erupted.
Now, if you have ever taken one of my classes, you know I stress the need to create a storyline with each image we create. Photography provides a wide range of tools with which to fine tune our storyline, including light quality, composition, lens focal length and many others. Arguably the most powerful tool in our shop, however, is the ability to control depth of field.
Depth of field is defined as the area of an image in front of and behind the plane of focus that is sharp. By changing the aperture setting, or f-stop, we control how much of our image is sharp and how much is soft. Because sharp detail is one of the components of an image that attracts a viewer’s attention first, this ability to guide the viewer’s eye gives photographers a powerful tool with which to show an audience what we feel is the most important aspect of an image. Every photographic decision we make impacts our storyline.
So, why would you want to make sure everything in your image is sharp? Landscapes are a popular subject where pretty much everything in the image has equal value, from the foreground to the background. Composition may be used to emphasize some component of the scene, but if everything is sharp, the photographer is indicating to the viewer that every aspect of the scene is equally important. Architecture is often handled the same way.
Maybe you have a subject within a larger environment. If everything is sharp, you are telling the viewer that both the main subject and the environment are equally important to your storyline.
Let’s look at the 3 techniques we use to create extreme depth of field.
#1 The first, and most obvious step, is stopping down the lens aperture. Remember how apertures work? The higher the aperture number, say f-16 to f-22, gives you the smallest lens opening and the greatest depth of field. This is why we need to take over setting the aperture on our camera so that we can control the amount of depth of field created by our aperture or f-stop setting. In this case, stopping down to f-22 gives us lots of depth.
#2 The second step is choosing a lens focal length. Wide angle lenses have depth built in and the wider the lens, the greater the built-in depth of field. This is not to say that a normal or telephoto lens can not achieve extreme depth, but a wide angle lens can achieve this depth even at midrange aperture settings of f-8 or so.
#3 The third step is a little trickier to understand. The greater the camera to subject distance, the easier it is to achieve great depth of field. As you move farther from your main subject, the difference between camera to subject distance and camera to background distance becomes less, making it easier to get maximum depth of field. If you move closer to your main subject, the difference between the two distances becomes greater and both smaller aperture and wider lens may be necessary to achievee the proper depth.
There you have it. The three tools for creating extensive depth of field in an image are smaller lens aperture, wider focal length lens and greater camera to subject distance. But remember, you need a reason to keep your background as sharp as your subject. Know what you want to say about a subject or location and then create the necessary amount of depth of field. This is a fluid system in which depth of field is almost always your first decision. Take control by setting your camera to “A “ or “Av”, Aperture Priority, and set your lens aperture appropriately. All of this is just a bunch of words, of course, until you set your camera to “A” and start adjusting your depth of field as you shoot.
“You don’t take a photograph. You make it.” Ansel Adams
Our next post will be geared towards creating shallow depth of field, a great technique for separating your subject from the background. Coming soon.