In the recent WWDC 2017 Conference, Apple announced two new file formats will be introduced with the new iOS11 - High Efficiency Image Format (HEIF) for photos, and HEVC (H.265) for both videos and images, and HEIF file format for images. Apple claims these new formats can reduce photo and video file size (presumably to save on memory) without losing quality.
High Efficiency Video Coding (HEVC) codec is not new. It has been used by Netflix, Amazon and Apple. The former used it for non-mobile devices while Apple used it for Facetime since 2015 to save on bandwidth.
9to5Mac's Greg Barbosa had access to a beta version of iOS 11 and did some tests on the quality of the image files taken with the new format :
"In testing I went out at night and took a photo and video of the New York City skyline. The outputted JPG image weighed in at 2 MB, while the HEIC image came in at 1.2 MB. Similarly, the h.264 encoded video was 61.2 MB, while the h.265 (HEVC) video was 33 MB."
Below is a photo from Greg to illustrate the new file format :