From https://discussions.apple.com/thread/250112022:
The only way to downgrade a Photos Library from Photos 4.0 Mojave to Photos 2.0 Sierra would be to use iCloud Photos Library. -Carl > On Jul 1, 2021, at 4:34 PM, Carl Hoefs <[email protected]> wrote: > > Oops, I just checked, and High Sierra did run Photos, but an early version of > the database. It did get updated often going to Catalina, though. > > -Carl > >> On Jul 1, 2021, at 4:31 PM, Carl Hoefs <[email protected] >> <mailto:[email protected]>> wrote: >> >> High Sierra ran iPhoto; Catalina runs Photos. The two photo database formats >> are totally incompatible, which is why it upgrades the database. And I know >> that somewhere along the way (from HS to Catalina) it did a forced upgrade >> of the mailboxes. >> >> So my guess is that your undertaking would be an exercise in futility... >> >> (And ditto your frustration with the iMac's gossamer-thin screen connection >> wires: What were they thinking?) >> >> -Carl >> >>> On Jul 1, 2021, at 3:51 PM, Macs R We <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> I have a client running Catalina on an old 2013 iMac with a spinner. >>> There's no reason he needs to be running Catalina (he still uses Lotus 123, >>> for heaven's sake), he is apparently just a low-information victim of >>> Apple's antisocial robo-nag campaign to "Upgrade! Upgrade!! Upgrade!!!" >>> >>> His machine is now crawling. >>> >>> My preference would be to clone his machine to an external, wiping it, >>> install fresh High Sierra, and then migrate his files back in. But I'm >>> unsure whether there have been format changes between HS and Catalina in >>> personal databases such as Photos, Address Book, mailboxes, and the like >>> that would queer this… or whether File Migration might just arbitrarily nix >>> the importation out of principle. Not to mention knowing that the System >>> Settings category (WiFi networks, Apple IDs, Sharing, Accessibility, etc.) >>> would probably be un-migratable in toto, but that's less important as it >>> can be addressed manually. >>> >>> Can anyone say if this reverse-migration is doomed before it's tried? >>> >>> The alternative would be to swap out his HDD with an SSD and clone it over, >>> which would be a more costly job in terms of hardware fiddlery time (I hate >>> working on iMacs, having to disconnect all the fragile display screen >>> connectors to do the simplest things), pus the cost of a new TB drive. >>> >>> (Damn Apple's irresponsible pressure on typical consumers to upgrade their >>> OSes.) >>> >>> -- >>> Macs R We -- Personal Macintosh Service and Support >>> in the Wickenburg and far Northwest Valley Areas. >>> http://macsrwe.com <http://macsrwe.com/> >>> _______________________________________________ >>> MacOSX-talk mailing list >>> [email protected] <mailto:[email protected]> >>> https://www.omnigroup.com/mailman/listinfo/macosx-talk >>> <https://www.omnigroup.com/mailman/listinfo/macosx-talk> >> >> _______________________________________________ >> MacOSX-talk mailing list >> [email protected] <mailto:[email protected]> >> https://www.omnigroup.com/mailman/listinfo/macosx-talk > > _______________________________________________ > MacOSX-talk mailing list > [email protected] > https://www.omnigroup.com/mailman/listinfo/macosx-talk
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