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One of the most distinctive characteristics of any photograph is its depth of field: Is the entire frame in sharp focus, from near-to-far, or only the subject? For a serious photographer, achieving the right depth of field isn’t an accident or trial and error; it’s deliberate and planned.
There was a time when photographers would carry a depth of field guide around with them—a small booklet filled with spinning dials and radiating grids of numbers that looked sort of like an engineering diagram for the space shuttle. These days, you can get the same information more easily using an iPhone app. And that puts precisely planned photos with just the right depth of field within your reach.
DOFMaster is the iPhone extension of the excellent DOFMaster.com, a website that offers ways to help you calculate depth of field from every conceivable format, including your browser, iPhone, Android phone, and a Windows app.
DOFMaster is the very picture of simplicity; the entire iPhone app occupies a single screen and features just five buttons. To get started, specify your camera. A drop-down menu lets you choose from among general categories like 35mm, APS, a number of medium- and large-format cameras, or compact digital. You can also select your specific digital SLR model.
Making the right choice is important because depth of field depends on the relationship between the size of your camera’s sensor and your lens. A point and shoot digital camera delivers a very different depth of field at a particular focal length than a digital SLR. And even among SLRs, there are a small set of professional caliber full frame cameras, and more common models based on the somewhat smaller APS-C sensor.
The app doesn’t list every camera on the market, past and present, but that’s okay—just choose a similar model or category that has the same size image sensor. You won’t find the Nikon D7000, for example, so just choose Nikon DSLR from the list. If you have a point and shoot camera, just choose Compact Digital.
Once the camera is set, choose a lens focal length and the f/stop at which you plan to shoot. Finally, enter the distance from you to your subject—the focusing distance—and DOFMaster immediately calculates the nearest and farthest limits of acceptably sharp focus for the shot. And that’s it.
Suppose, for example, you have a 50mm lens on your Nikon D7000, and you want to shoot portraits of someone 10 feet away. Plug in the pertinent details, and you’ll find that at f/4 you’ll have a thin 2 feet of depth of field, from 9 to 11 feet. Dial the lens to f/16, on the other hand, and the depth of field extends from 7 feet all the way to 16 feet in front of the camera.
This makes DOFMaster not just a great pocket guide to calculating depth of field, but a useful teaching tool as well. The app doesn’t just show the relative effect of varying depth of field, but it does it for your particular camera. That’s indispensable for mastering the art of photography.
The app has one other trick. At the bottom of the screen you’ll find a button marked HD, which calculates the lens’s hyperfocal distance for the selected f/stop. Hyperfocal distance is the distance at which you need to focus the lens to get the deepest possible depth of field. If you want to take a photo that’s in sharp focus from the very foreground all the way to infinity, you’d set the f/stop to the smallest aperture (say, f/22). You might find that if you focus the lens 18 feet in front of you, then everything from 9 feet to infinity will be in focus.
Most people happily take snapshots with their camera, never agonizing over achieving the right depth of field. This app is not for them. But if you would love a simple way to know if you have enough depth of field to ensure your kids and the statue they’re standing in front of are all in sharp focus, or if you yearn to take more control over your art photography shoots, then DOFMaster is a prudent $2 investment.