I really like this app. I recently toured an art exhibit where the ability to control the camera settings and to use the bracket exposure feature, was very useful.
The problem was that the app froze many times. I had to quit the app to get it to work again. Eventually I went back to the phone camera. So download it, enjoy using it, but be prepared to have it hang just when a really great picture comes along.
6S phone with latest iOS.
Kerly31415 about ProShot