This app provides a limited amount of exposure control for the iphone 5s camera. You can set a manual shutter speed, and the app will figure out the rest of the exposure parameters, within limits of the device. The native iOS7 camera app takes nearly as good photos as this app does, but you have slow exposure control with this one, if youre doing tricky shots like night portraits, where you need to fire the flash to light up the subject, but you need delay to get the background; and for that sort of use, its pretty good.
Where it lacks, and what I was hoping for with this app, was full (or fuller than this) P/A/T/M exposure settings. I want full manual exposure control; f-stop, ISO, shutter speed, and this app doesnt do it.
So, 3 stars. For $0.99, its probably worth the money, providing you one extra control for the camera, but youre still not going to be able to leave your tiny point-and-shoot camera at home if youre planning to take pictures. This mostly extends the range of utility in the "whoops, i forgot a real camera" situation.