Auto Distortion Control
Explanation: „Distortion“ means that a lens will project a straight line into a slightly bended one on your picture – how much is dependent on your lens and in case of zoom lenses also of the focal length.
The auto distortion control enables a correction.
Tips: I leave this function switched off because it does not work fully accurately. For a really exact correction of distortion you best use an image processing program that has a dedicated function for this and applies corrections specific to your lens.