I haven't yet updated my iPhone to iOS 11 yet. Has anyone encountered this problem of the update saving photos as .heic files instead of jpegs? They explain how to make the change back to jpegs--which all of us might want to consider doing before shooting.
https://petapixel.com/2017/09/25/make-iphone-shoot-jpegs-ios-11/
https://petapixel.com/2017/09/25/make-iphone-shoot-jpegs-ios-11/