iCloud Adding previously offline mac photos to iCloud Photos

[Bill Forest]

Hi,
I have an iphone and ipad that are both connected/synced to my iCloud Photos account. I also have an older offline iMac that is running Photos version 3.0. Since this iMac is offline, it is not connected to my iCloud Photos account.
I manually download my iphone photos to this older iMac with a USB cable from my iPhone, and then I edit the photos on my iMac. This means that that the photos on my iMac are often different versions than are those in the cloud (even though the filenames are the same)

My Question:
For simplicity's sake--let's say that I have 10 photos in iCloud Photos, and the same 10 photos manually downloaded to the old offline iMac/Photos app.

I then edit, crop, etc. the photos on the old offline iMac, so that they are no longer the exact photos that are in iCloud photos, even though their filenames are the same.

If I then connect my old offline iMac to the internet and to my iCloud Photos account, what happens when the old, previously offline iMac goes to sync with iCloud?
Will I lose the edits that I made on the old, previously offline iMac?

Will it keep all 10 of the iCloud photos, and then ask me if I want to keep a separate copy of the photos I edited on the old, previously offline iMac?

If I previously deleted a photo on the old, offline iMac, will it then delete that photo in iCloud Photos?

(In reality, I have about 50K photos on the old, offline iMac. I want to connect the old, offline iMac to my iCloud Photos account, but don't want to lose the work that I have put into editing the photos on that iMac)

Last, once I connect my old, previously offline iMac to my iCloud Photos account, will iCloud Photos simply look at the dates to decide which version to keep, and then keep only the most recent?

For example, if I edited a photo on my old, previously offline iMac, will iCloud Photos look at the edit date, and if the date is more recent than the photo in iCloud, will it simply replace the older version in iCloud Photos with the more recently edited version from my old, previously offline iMac?

And, if iCloud Photos DOES use the date and replaces the older version in iCloud Photos with the more recently edited version from my old, previously offline iMac, will I still be able to use the Revert to Original command if I want to go back to the original?
Thanks for your help.

 

[BigBlur]

Just hypothesizing here, but I'm pretty sure you would end up with duplicate photos for a couple reasons:

• iCloud Photos does not care about the filename. You can have multiple photos with the same filename in iCloud Photos (and even in the Photos app for that matter).
• iCloud Photos has no previous context or sync history with the photos that are on your offline iMac; so as far as iCloud Photos is concerned, they're new/unsynced photos.

With the above in mind, the offline iMac would download the photos that are in iCloud Photos and upload the existing photos that are on the iMac. Your iPhone and iPad would also start downloading the "new"/duplicate photos that were uploaded. Essentially, the two libraries would be merged, but none of the photos themselves would be merged or replaced with another.

If you're still wanting to turn on iCloud Photos for the iMac, the safest way would be to either:

• Create a new photo library on the Mac and set that as the System Photo Library for iCloud Photos to sync to.
  • You can still access the old photo library on your Mac if needed, but be careful when turning on iCloud Photos...make sure the right library is set as the System Photo Library.
• Clear everything out of iCloud Photos first before turning on iCloud Photos from the Mac.
  • This is assuming all the photos are already on your Mac, but you would lose the edited versions of your iCloud Photos.

Since it sounds like your iMac is the "master", the second option would probably be the way to go.

 

[Bill Forest]

Thanks so muchBig Blur. I can follow what you said pretty well. I will go the route of creating a second library on the previously offline iMac. Thanks, again.