Gentlemen Coders got back with me and gave me this (and I am tempted to buy Nitro just on the quick response and good explanation)
Due to the way Macs work these days (in terms of security), it’s not really possible for a third party app like Nitro to modify the way Photos would work, or to add camera support to all apps on the system. So, Nikon support is limited to when you are using Nitro itself.
Because Nitro is fully non-destructive, it never modifies the original file. You can always revert to original. Normally, Photos Revert to Original will do this, but for completely unsupported images like Nikon HE, their Revert is broken (this actually used to work in Photos).
So, in that case, the best thing to do is Revert in the Nitro app itself. I ran your specific test cases as follows:
- Imported Nikon HE into Photos
- See blank thumbnail; go into Edit get an error
- Open Nitro Extension
- Make Black and White; Save
- Looks fine in Photos.
- Use Retouch in Photos
- Cannot Revert in Photos
- Go to Nitro (the app)
- Revert to Original - it works there
- Go back to Photos and there is a blank thumbnail, just like in Step 2.
If you edit in Nitro and then in Photos, you are working with either a JPEG that is created by Nitro. That is also true in reverse. If you edit in Photos and then in Nitro, then Nitro gets a JPEG. This is the way Apple has designed Photo Extensions.
So, unfortunately, because of bugs in Photos, you cannot revert in Photos if it’s an unsupported RAW image. However, your images are always safe, and you can revert in Nitro (the app).
I hope that helps.