The iPhone 11 shoots in the HEIF format as the default. Apple started using HEIF with iOS 11. You can change it to jpeg, but HEIF is better. HEIF uses a 16-bit deep color, jpeg is only 8-bit. HEIF files are about half the size of jpeg files. HEIF files end in .HEIC . They can be a pain
because not all computers can view them without a HEIC viewer. Windows 10 can view them if you are on at least Build 17123 , and with Macs, I think you need to be on at least High Sierra.