Importing this media via USB
When you import HEIF or HEVC media from an attached iOS device to Photos, Image Capture, or a PC, the media might be converted to JPEG or H.264.
You can change this import behavior in iOS 11 or later. Go to Settings > Photos. In the TRANSFER TO MAC OR PC section, tap Keep Originals to prevent the media from being converted to JPEG or H.264 when importing.
Sharing this media
iCloud Photos preserves media in its original format, resolution, and frame rate. If your device can't fully view, edit, or duplicate HEIF or HEVC media in iCloud Photos, or displays it at a lower resolution, upgrade to iOS 11 or later or macOS High Sierra or later.
When you share media using other methods, such as AirDrop, Messages, or email, it might be shared in a more compatible format, such as JPEG or H.264, depending on whether the receiving device supports the newer media format.