Continuing the background on the new photos infrastructure. As we expand our view outside of the iOS devices Apple works very hard to manage data to simplify user interaction with differing file formats. You can find a list of supported cameras here : Digital camera RAW formats supported by iOS 11 and macOS High Sierra. Apple regularly adds new cameras and their formats to their Operating Systems. Their RAW file conversions are very good.
With iOS 11 Apple changed the file format that the native camera which for them should be relatively simple to manage. Apple has chosen to only support the the new file format fully in macOS High Sierra in their Photos application. So if you want to use Photos you have to upgrade your Mac to High Sierra. If you are using Windows PCs there will be some lag in support because Windows applications have to build their own support for different file types as the OS does not help with this. Even Apples photos tools on the PC had not been updated at the time I write this.
For professional photographers working on the Mac this change really means nothing. We are used to managing RAW files in our normal work flows. We do not send the RAW files out to our customers or to the photo lab that cannot use them.
In Apple Photos understand that exporting the original file will give you the HEIC format that may not be viewable on say a Windows PC or a Mac running older versions of macOS. Note that the sharing systems on iOS and OS X convert to JPEG for compatibility.
If you are managing your iPhone images manually you will also run into this potential problem.
Using the Apple supplied systems of the iCloud Photo Library and Apple Photos virtually eliminates issues for most users. So when you start using iOS 11 and the new image formats you have too upgrade your devices that sync to iCloud to the iOS 11 and macOS High Sierra.