Easy way to permanently delete all photos and videos from iPad/iPhone

It seems really hard to me to permanently delete all photos and videos from iPad. I tried different solutions, like:

• Transferring them using iPhoto and then deleting them by iPhoto


• Using iTunes to sync the photos from an empty folder on Mac

While these solutions resulted in deleting some photo folders on iPad, some other folders (i.e. My Photo Stream) remained unchanged. Then I tried to remove them by selecting the photos on iPad but there were too many pictures. Finally the "Recently Deleted" folder on iPad remained full of photos! And iTunes shows there is a huge space on iPad still used by photos and videos.

So what's the easiest way to tell iPad I don't really want any more photos and videos on it?