With each new version of iOS, Apple delivers hundreds / thousands of new APIs to developers and makes the system more "open", flexible. Like iOS 8, it now allows apps to control just about everything related to the iPhone camera.
With that, excellent new apps like Manual.
As the name implies, the Handbook for those who like to have complete control over their photographs. It offers independent adjustments for shutter speed, ISO, white balance, focus and exposure.
And the Manual goes further, with a real-time monitor for checking exposure values, histogram, flash fill mode, alignment grids, EXIF information viewer, day / night themes, among others. Another nice thing is that the photos taken by him go directly to the Camera Roll of the device.
(via Daring Fireball)