27.12.2012, von Dave Johnson
There are plenty of iPhone apps that improve or expand on the basic camera built into the iPhone and iPad. You can think of BlueStone Pond's , on the other hand, as a $4 app designed to replace the old-fashioned depth of field calculation wheels, which serious photographers sometimes threw into their camera bags back in the days before the Internet. You can use SetMyCamMx as an interactive tool for fine-tuning your exposure to ensure you're choosing the right settings to capture your shot.
SetMyCamMx's primary job is to help you figure out how to get the depth of field you need for a particular shot. Just dial in the focal length of your camera's lens, an f/stop, and the distance to the subject--the focusing distance. SetMyCamMx will immediately tell you the closest and farthest distances at which the camera will be able to deliver an acceptably sharp focus. In other words, it tells you your depth of field.
That makes SetMyCamMx a superb learning tool as well as a field guide. You already know that a larger f/number gives you a greater depth of field. But SetMyCamMx will tell you exact numbers: 50mm at f/5.66, focusing at 10 feet gives you 3.3 feet of depth of field. At f/32, the same lens and focusing distances delivers a huge 65 feet.
Even better, SetMyCamMx shows you all this visually. Every calculation is accompanied by a graphical depiction of your camera, the subjects, and a yellow rectangle that represents the depth of field. You can get the same data from other depth of field calculators, but SetMyCamMx shows you the data in a way that leaves no room for confusion.
That's handy if you want to find the answer to settings questions like, "is my depth of field deep enough to include all the people in this scene, but not include pedestrians walking a few feet behind," but often you are looking for something else: The hyperfocal distance.
While it has an intimidating name, the hyperfocal distance is simply the distance at which you need to focus your lens to ensure that you get the maximum possible depth of field at any given f/stop. And SetMyCamMx tells you that at the bottom of the screen in plain English. Using a 50mm lens at f/5.6, for example, you should focus the lens (using the camera's manual focus control) to 72 feet. If you do that, everything from 36 feet to infinity will be in focus. You'll get better hyperfocal performance at f/22, though--if you focus the lens at 18 feet in front of you, everything from 9 feet to infinity will be in sharp focus.