multiple photo libraries vs. referenced libraries

since the system library is basically the master?

You may want to read this Help page.

https://help.apple.com/photos/mac/1.2/?lang=en#/pht211de786

The System Photo Library is independent of other Photos Libraries, you may create, but some services are not available for photos in other libraries.

• As TD already pointed out, the system Photo Library is the only library that can be used with iCloud services.
• And it is the library, that is used, when other apps are using the Media Browser. iMovie, Mail, Safari, iTunes, Pages, and others will show you the photos in the System photo Library, when you want to access your photos using the Media Browser. All Photos you want to access from other applications should be in this library.
• And other apps will save a photo in your system Photo Library, when you use the command "Save to Photos" I another application.

The Media Browser behavior of Photos is different from the way it used to be in iPhoto and Aperture. Previously, for Aperture or iPhoto, the Media Browser would show simply the library we last had been using. This is different in Photos. We specify the library to be used with iCloud and the Media Browser. Switching to other libraries does not change the library to be used by the Media Browser. In the Media Browser we are limited to the current system photos library. Switching is expensive, because it will cause the complete library to upload again to iCloud.

If you split a library into multiple libraries all of the libraries will be the same as the original library. You can't have one library managed and another referenced. When you set Photo's preferences to "managed" all libraries opened with Photos will be considered managed.

and note that referenced libraries are not recommended and are a bundle of future problems with Photos - Disadvantages of a Referenced Library in Photos

You probably want multiple libraries (although multiple libraries can each either be referenced or managed

LN

however, if I split the libraries, is that alternate library considered a managed library or a referenced library?

Neither. it's an alternative library.

A Managed Library, is the default setting, and Photos copies files into the Photos Library when Importing. The files are then stored in the Library package

A Referenced Library is when Photos is NOT copying the files into the Photos Library when importing because you made a change at the Photos -> Preferences. (You unchecked the option to copy files into the Library on import) The files are then stored where ever you put them and not in the Library package. In this scenario you are responsible for the File Management.

I'm guessing you mean setting-wise and not along the lines of all the photos will be the same. Correct?

Correct. You can have a reference and a managed library but each time you open them you have to change the copying setting for that library. It's not a good idea as it's easy to forget to change it back from a referenced to a managed when opening a supposedly managed library and lose photos that are added to the library. I know, I've done it.

What I'm wondering now is if I split my photos into multiple libraries, can I delete the photos in the system library after putting them into the second library or will deleting them from the system library delete them everywhere (including the second library) since the system library is basically the master?

The System Library is not a Master in any sense of the word. It's just the library linked with the iCloud Photo Library. That's the only difference between it and any other library. So, yes if the photo is in a second library you can delete it from the System Library. But it will also be deleted from the iCloud Photo Library.

If you don't use the iCloud Photo Library then, basically, the term System Library means nothing.

Previously, for Aperture or iPhoto, the Media Browser would show simply the library we last had been using. This is different in Photos. We specify the library to be used with iCloud and the Media Browser. Switching to other libraries does not change the library to be used by the Media Browser. In the Media Browser we are limited to the current system photos library. Switching is expensive, because it will cause the complete library to upload again to iCloud.

Wow. Hadn't realised this. Well another major reason to not to use the app.

That is why it is an optional program 😉

LN