How to Make Your iPhone Use JPG and MP4 Files Instead of HEIF and HEVC

In iOS 11, the photos and videos you take will no longer be encoded in the compatible formats you’re used to. Instead of JPG for images and MPEG-4 for video, they’ll use High Efficiency Image Format (HEIF) and High Efficiency Video Format (HEVC), respectively. Files in these newer formats are about half the size of JPG and MP4 files of similar quality.
by Harry Guinness via How-To Geek