I would recommend you to re rate the images in the Lightroom. As it will not be able to recognize the favorites that you have assigned Photos.
With over 1000 of these, I was hoping there was a solution other than treating them manually. I'm surely not the only person in this situation. After all, this is a big barrier for many people thinking of moving to Lightroom. Alternatively, maybe I should just move to the Apple ecosystem?
Are these 1000 in Lightroom already? If not, can't you put them into an album in iOS and then import them separately from the other 10000?
No, I don't believe you're the only person with this problem. With new pictures, you can just bring them straight into LrMobile and rate / flag them there, but your backlog is pretty large and Apple's ecosystem is still pretty new and a bit of a black hole.
They (mostly) aren't in Lightroom yet which makes this potentially easier. I don't want to just get the 1000 into Lightroom, I want all of them. But it could be I could get them all; then import the album of favorites; and then have Lightroom find duplicates. I could then put a keyword on all the duplicates.
What I'm trying instead is to load them all from iCloud into Photos App--which preserves my "favorites" album rating. Then I can add a keyword to the rated ones (like "favorites"). Then I should be able to export the photos, preserving metadata. Since they're already .JPGs, I don't think (?) I'll lose information.
The downside of this approach is that I can't figure out a shortcut way to download everything directly off my phone. (Maybe I could, with iTunes? not sure). They already live in iCloud, and the default Photos approach is to download them all over wifi. Overnight it downloaded all the thumbnails; since then it's downloaded 700 pictures, with 11,322 left to go...They are all downloaded into a large Apple/proprietary database.
My fear is that I'll find a snag in my plan to export them or some such....but all I will have lost is some time. And it's not making me want to stick in the Apple/Photos ecosystem!
Thanks to all for the help. To close the loop on this query, here are the steps I followed. They turned out to be relatively straightforward, though a bit slow. I had six months of photos that I'd rated only on my iPhone, but hadn't yet imported or processed in Lightroom. So there was no overlap. Otherwise, I would have surely needed to re-rate them.
- Download all photos from iCloud to the Photos App on OSX. (This was slow--it did it wirelessly, which took a few days. I couldn't figure out a faster way to sync directly without going through iCloud.)
- In Photos, select the "Favorites" album (which had the 1,000+ ones that I'd "hearted" on my iPhone). Add a keyword "favorites" to those photos.
- Export all photos from Photos to my hard drive. Confirm that the keyword went with it.
- Rename the photos using ExifRenamer so photo names showed dates and times, plus the original filename (so, for example, IMG_1234.jpg became 2015-12-08_21h58m25s_1234.jpg)
- Download videos from iPhone separately using ImageCapture, and rename with ExifRenamer. The reason is that, when Photos exports videos, all information about the shoot date/time gets lost.
- Import into Lightroom
- Confirm that keyword "favorites" showed up in LR. (For unknown reasons, I had to do steps 3-7 twice. I had started by doing an experiment with a few pictures, and it worked; but when I did all photos, the keywords had gotten lost somewhere between steps 3 and 6).
I will improve my workflow going forward to avoid having to do all of this again! I also realized I don't want to stay in Apple's ecosystem (with all photos in their own massive, proprietary database) :-)