Will deleting a picture in Photos, delete the original in Finder?

It depends on whether you have a managed or referenced library.

If you have a managed library and delete a photo from the library the master file that was copied into the library during the initial import will also be deleted. However, if you left the source file that you originally imported somewhere on the hard drive it will not be deleted. If you're like most users with a managed library you've deleted the "source" file after importing it so don't have to worry about it.

If you have a referenced library and delete a photo from the library the referenced, source file that resides elsewhere on the hard drive will not be deleted.

Many

Importing is a two step process as is deleting

The path to the originals must remain the same which make replacing defective hardware or upgrading hardware or moving to a new system difficult or impossible

It is very easy for user error to occur causing problems

and in version 1.0 (and maybe later) was reported to use more storage in the main library than if you copied the photos - that may or may not be resolved in version 1.0.1

and there are no advantages - only disadvantages

LN

No, if the original that was imported is in a folder outside of the library.

Also, referenced images cannot be used with iCloud Photo Library. This was written for iPhoto, but it remains largely true for photos too:

https://discussions.apple.com/docs/DOC-6361

Yes, assuming you have a managed Library.

Note that referenced libraries are not a good idea in Photo, have no advantages and many disadvantages and are not recommended

LN

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