Photos - iCloud - old iPhotos

Here's some general stuff I wrote a while ago. It might be a bit simple, but it establishes a vocabulary so we can speak the same "language."

The Photos app contains the instructions for dealing with a database that contains information about your picture files. On a Mac, the Photos app can be found in the Applications folder, and probably in the Dock of apps at the  bottom (or, in my case, on the side) of your Mac. The Photos app isn't a huge file, because it doesn't have any pictures, just instructions.

The Photos Library is a package (a slightly protected folder that has stuff you're not supposed to mess with) that contains the database and the Original picture files. It also has stuff like Thumbnails (the tiny pictures in the grid view of Photos) and Previews (screen sized images for showing quickly.) On a Mac, the Photos Library is kept (usually) in the user's Pictures folder. The Library is big, many gigabytes, because it contains all the pictures. On a Mac, you can have several Libraries and switch between them, but only the one called the System Library can be connected to iCloud. On an iPhone or iPad there can be only one Photos Library, and you can't see it or access it directly. You can (and should) make backups of the Photos Library by copying it to an external hard drive.

The System Library is the Library that apps, like Messages, or Screensaver, or Safari, go to when they use a picture or save a picture in Photos. It is the only Library on a Mac that can synchronize with iCloud Photos.

The database is where all the information is stored for the pictures. As you add keywords or captions or titles, for instance, those aren't attached directly to the picture file, but they are stored in the database. This metadata is attached to the file (if you so instruct) when the file is exported for use outside of Photos. In fact, the Original picture file is never altered-- it remains available exactly as it was loaded no matter how you may make changes. The changes are recorded in the database, and they are applied when you view the image. Previews are smaller, temporary screen sized images that show the edits, but full sized edited images are created on the fly from the editing changes that were recorded. Even the original filename is no longer attached to the image-- a unique name is created for the file, and the original filename is stored in the database.

iCloud Photos is a synchronization service. When you engage iCloud Photos on a device, then the Library on that device is kept exactly the same as the iCloud Photos Library. So, for instance, if you take a picture with your iPhone, it is added to the iPhone's Photos Library, copied to iCloud Photos Library, and then copied to the Photos Library on each of the other devices. If you delete a picture on your Mac, then that picture is deleted at iCloud and on all the other devices. 

You can use Optimize Storage on the Mac, on your iPhone, or on your iPad. You can set this on any device, independent of the others. You are not required to have your Mac hooked in to use "Optimize Storage" on your phone. If you want, you set this in the Photos Settings on each device. If you set a device to "Optimize Storage," then Photos may store only smaller images on the device and rely on iCloud to keep the full sized images. So, if Optimize is chosen, and you want to magnify a picture to see more detail, Photos will reach out to iCloud to get a full sized image for you to zoom in on. It's the same for editing or printing or anything that demands the full picture. Your optimized Library may take up less than 20% of the space of a fully downloaded Library. But an optimized Library may be kept larger than that if the extra storage space is not needed.

Beware, though: backing up a Mac Photos Library with Optimize Storage only backs up smaller images. If you want to keep a true backup on an external disk for safe keeping, you need to have Download Originals checked on the Mac. 

 In the above I was referring to a Managed Library, in which Photos hangs on to all the Original picture files in its Library. There can also be a Referenced Library where the Original picture files are kept in Finder folders and are not added to the Library at all. A Referenced Library is really for testing purposes, and accidentally creating a Referenced Library has caused lots of troubles for people. Almost no one has a Referenced Library. Managed is the default, so that's bound to be what you have. In Mac Photos Settings>General, "Copy Items to the Photos Library" should be, and probably is, checked.

I'm happy to do more-- see if this changes your questions…

GinaBeana wrote: … I have a photolibrary BACKUP from August 2, 2024. So I'd want to restore the photos deleted since that date. … Maybe I have to turn off sync first?

You can look for the missing pictures in "Hidden" or "Recently Deleted" (where deleted pictures may be held for 30 days) on any Library you can find on any device you have including at iCloud.com. If you don't see them anywhere, then they're gone. "Sync" means making everything the same. Turning off syncing means no more making the same. It doesn't add things or reveal hidden things.

Question: What happens if I upload photos from my Mac Mini’s desktop to my Photos? Do the photos then appear on my Iphone, too - up to the storage limit setting on my phone? Then, when it surpasses the limit, it deletes willy nilly?

If you add pictures to one device that's connected to iCloud, (including uploading to iCloud Photos,) then those pictures are copied everywhere else. Photos does its best to avoid duplicates, but they sometimes happen. When storage gets full, then new things like adding pictures or deleting pictures or editing pictures becomes pretty much impossible. No picture gets deleted without action by the user, intentional or accidental. It seems to me (with no actual research) that the most common way that pictures get "mysteriously" lost is when people try to move pictures from one place to another, but don't check to see if it really happened the way they thought.

I use "Optimize Storage" on my iPhone, because I don't have much storage, there, and I don't edit pictures on it. I have "Download Originals" on my Mac, and I've moved a lot of stuff (not pictures) to an external drive to make room for Photos. I have extra Libraries on an external drive, as well. "Download Originals" allows me to back up my Libraries to external drives. I would do anything necessary to not use "Optimize" on my Mac. I also have "Download Originals" on my iPad, because the big screen makes viewing and editing more likely, and I bought plenty of storage on the iPad.

Question: Does iCloud create a "mirror" on my Mac Mini of the photos in my iPhone?  And to do that, it deletes whatever was in the library up to my bad decisions to use iCloud (or use it incorrectly)?

I think I answered this one: It's not a mirror of your iPhone-- all devices are kept exactly the same. The iPhone "mirrors" the Mac, and vice versa. Pictures can be added, but they don't get deleted without you doing it. If you're iCloud Photos has pictures A to F, and you connect a new iPhone that has pictures G to N, then iCloud, the new phone, and all your devices will have pictures A to N.

By the way, adding pictures from the Mac to the phone, or the reversed, by using a cable is not compatible with Photos. Adding pictures by cable is way inferior to syncing with iCloud. With a cable, there's no guarentee that all the information transfers.

How are we doing?

What you've shown is not the Photos Library. Earlier I said: "The Photos Library is a package (a slightly protected folder that has stuff you're not supposed to mess with) that contains the database and the Original picture files." That "not supposed to mess with" was a warning! If you move files around, or accidentally change one, then the database may not be able to put all the pieces back together again. The Photos Library package is usually named "Photos Library.photoslibrary" and it's kept in the Pictures folder.

Time Machine backups don't make the individual pictures available. You can find the Library package in the backup, and restore the Library. I haven't done that in a while, but I think that you're given the option of keeping both the restored one (with a slight name change) and the existing one. If you don't see that, you can move the existing Library to a new folder, and then restore the recovered one to the Pictures folder. You should be able to double click it and open the Library in Photos. You can switch back and forth by double clicking, or you can use the Library Picker--close Photos, option-click on the Photos icon, and you get a dialog showing you Libraries that Photos knows about. You can choose which to view.

GinaBeana wrote: … What I can't figure out is why years of photos went missing on my Mac Mini Photos when I did NOT delete them from my iPhone.

Yeah, I get that. Of course, I can't know how that happened. I can tell you that I've never seen anything like that with my Photos Libraries.

But just in case, I do a Time Machine backup at least once a day, and I copy my Library to another external drive every month or so (unless I forget, darn it!)