Photos when reverting from El Capitan to Yosemite

[RadioChuck]

I've managed to revert from El Capitan to Yosemite on my MacBook Pro with relative ease. The only issue I experienced was with my Photos library. Apparently El Capitan converted the database and now I can not just copy that back over from my external drive like I did with iTunes.

The good news is that I didn't even realize that I had that many photos on my MacBook, and they're probably dupes of what's on the other computer. My Mac Mini is a different story, though. I have lots of pictures on there (a couple thousand, perhaps) that I would hate to lose. Can someone recommend a proper backup procedure that will allow me to step backward with my Mac OS and still be able to keep those photos. I would prefer not to use iCloud, but would consider that IF I can restore from iCloud and then remove the online copies of those photos.

Thanks in advance for any advice.

EDIT: This is all being done with the intention of restoring or importing into Photos in Yosemite, with as much metadata surviving the process as possible. Thanks!

 

[Ebenezum]

Photos library incompatibility was noted in developer documentation before El Capitan was released.

Unfortunately I don't think it's going to be easy process.

Option 1. If you have backup made before El Capitan you could try exporting all new pictures you have added to El Capitan Photos library as folders and importing them to Yosemite Photos. Some metadata might be lost.

Option 2. If you don't have a backup before El Capitan then you have to export all pictures and import them to Yosemite. It is likely more complicated compared to option 1.

Option 3. I haven't tested this personally but in theory you might be able to restore pictures from iCloud assuming Apple hasn't made any changes in the format. Since Apple changed the format between Mavericks and Yosemite I wouldn't be surprised if there are further changes which make them incompatible with previous OS.

Option 4. Ditch Photos and replace it with third party software. Obviously lot of work and may be costly but you are independent of Apples decisions regarding Photos.

For the record, these kind of incompatibilities are the reason why I never update OS in my main drive at launch date and I will make all compatibility testing on separate hard drive which has no valuable data, before any OS upgrade I also make several clones so I can easily revert to previous OS if necessery.