As amateur photographers grow in skill and move to more sophisticated cameras, one of the challenges they face is learning how to control depth of field. Depth of field—the portion of a scene that appears sharp and in focus—is a critical element in artistic control and the quality of a photograph.
By controlling depth of field, for example, photographers can throw a distracting background into a blur, while keeping a subject’s face in sharp focus. But since most point-and-shoot cameras automatically optimize the depth of field for a given situation, new SLR photographers can be in for unwelcome surprises, even during routine shoots.
With a little training and some experience, photographers can quickly grasp the essential concepts. A wide variety of iPhone apps promise to help tame the sometimes complex calculations needed for success. We examine three in this roundup, each focused on satisfying different types of photographers.
Depth of field can be a complex topic because of the many variables involved. Here is a quick review for beginners. The first variable is aperture, the amount of light passed by the lens, measured in f-stops. The narrower the aperture, the greater the depth of field. (Aperture and f-stops can themselves be confusing for beginners, since they’re inversely related. As your f-stop increases-say to f/16-less light is actually passed. A low f-stop, such as f/2.8, allows a great deal of light through the lens.) The distance to your subject is the second variable. The closer your subject, the less the depth of field (which is why close-up macro shots may have a depth of field measured in fractions of an inch). Finally, consider the focal length of the lens—the longer the lens, the less depth of field.
So far, so good. But the interplay of variables can lead to trouble for the unsuspecting. If you’re shooting a large group of people on an overcast day, for example, you may need a low f-stop to achieve the proper exposure. But that low f-stop will result in a shallow depth of field – leaving some subjects out of focus, unless you compensate. Depth of field calculators help beginners and pros alike quickly sort out these details to ensure the desired results.
First up is f/8 DoF Calculator from Bitzwerk. f/8 takes a functional, “all business” approach to the task. Calculations and adjustments are made on a single screen which—while easy to read—assumes you possess a good grounding in the subject. You adjust aperture and distance variables via sliders, while a simple panel details the total depth of field, the distance of the near and far limits of the zone of focus, and the distance it extends in front of and behind the subject. As with the other apps I tested, you’re able to select either metric or customary units for distance.
All of the apps provide a “camera bag,” where users detail the different camera bodies and lenses they have on hand. In f/8, cameras are pre-defined using an extensive database of more than 800 different bodies. You can also specify different sheet film sizes and cinematography settings, along with custom descriptions. There’s no database for lenses—you specify a minimum and maximum focal length (identical for fixed lenses), maximum aperture, and minimum focusing distance. When you’re ready to shoot, simply select the combination of camera body and lens you’re using and start making calculations.
In use, f/8 offered the easiest way to pick and choose gear of the three applications. The application is quick and easy to use, and it’s a solid choice—especially for more experienced shooters.
Dr DOF from Phozmo takes a unique approach to the job in delivering reams of educational and informational content along with its calculator. You perform calculations in three ways. First, a Quick Calculator allows you to specify basic variables and asks for the type of shot—macro, portrait, or landscape. The DOF Expert mode drops the graphics, while enabling greater precision in measurements and more detail on results. The Expert calculator also provides an option to reverse engineer calculations by providing the settings required to achieve a specific depth of field.
The final option employs a clever, and helpful, set of example photos. Select the type of shot you’re trying to create, and the application offers a set of exposure recommendations. From the advice screen, you can jump directly to either the Quick or Expert calculators. Dr DOF also delivers a comprehensive set of definitions and guides that further aid learning photographers. Unfortunately, Dr DOF’s camera bag was the most cumbersome of the group of apps I reviewed. The camera database was not as large, and camera and lens combinations need to be defined in advance, adding additional steps to setup.
Still, the ample supply of educational material will more than balance out the ease-of-use problem, especially for beginners.
PhotoBuddy from Ambertation delivers a Swiss Army knife-like combination of photographic tools. The app calculates depth of field using settings to the camera body and lens in use, or through an intuitive, interactive graphic which reveals the relative depth of field along with near and far limits. With the graphic, which can be turned off, settings are adjusted by sliding elements back and forth. Full details of the results of the calculation are presented in a table.
But PhotoBuddy doesn’t stop there—the application provides nine other helpful photographic tools. You can predict the time of sunrise and sunset; calculate exposure settings while manipulating aperture, shutter speed, and ISO settings; determine proper exposure when using flash; determine angle of view; and more. A few of the calculations are performed automatically by today’s cameras, but they’re still useful as learning tools, or for going old-school with manual adjustments.
With an attractive interface and a wide range of functionality, PhotoBuddy will be a useful addition to any photographer’s bag.
While each app seeks to satisfy a different audience, they all appear to perform their core task well. Tests of the calculations performed by each of the DOF calculators yielded consistent and accurate results. Buyers should make their selection based on their own unique requirements and experience levels.
[Dale Gardner is a freelance writer and aspiring photographer who lives in Northern Virginia. You can follow him on Twitter.]