Developer: Thorsten Kramp
Price: $3.99 Download on the App Store
f/8 is a simple app with a sophisticated purpose: It helps you calculate depth of field (DOF).
Here's a quick and dirty explanation for the layperson:
DOF is the distance in focus in front of and beyond the object you're taking a picture of. Let's say you want to take a picture of your mother-in-law standing on the precipice of the Grand Canyon. If you want the dear, sweet lady to stand out by having the Grand Canyon behind her to be out of focus, you would use a short DOF, and the way you would do that is to adjust the lens opening (called the aperture).
Now, if you want dearie and more of the Grand Canyon behind her to be in focus, then you would lengthen the DOF by using a smaller aperture.
IStockPhoto has a more comprehensive explanation along with several photos. Which aperture setting you would use is more of an artistic decision and seldom a technical one.
f/8 lets you select your camera model and lens and then enables you to calculate DOF using a variety of settings in metric and increments of meters or feet.
f/8 works well and the interface is clean and the options are comprehensive. Some App Store reviewers have given it low marks because they don't understand its purpose, so I would factor that into my decision whether to buy this app. I think it's worth the asking price.
This is not an app for anyone other than a serious photographer. I suspect most people with simple cameras wouldn't bother calculating DOF and messing with aperature settings.