A photograph contributed to an iCloud Shared Photo Library moves from the contributor’s personal library into the shared collection. Deleting it is therefore the wrong action when your intention is to keep your photograph privately while withdrawing it from that shared collection.

This guide concerns iCloud Shared Photo Library, not Shared Albums. Apple’s Mac setup guidance requires iCloud Photos and describes compatible participants using macOS 13 or later. Check the feature name before applying instructions to an older or different sharing arrangement.

Identify the contribution and intended result

In Photos, choose View, Shared Library. Select a small group that you contributed and want to return to your personal library. Confirm the contents carefully, particularly if several participants photographed the same event.

Choose Image, Move Photos to your Personal Library, using the item count shown in the command. Apple limits this move to your own contributions; you cannot use it to move another participant’s contributions into your personal library.

After the move, inspect your personal-library view and open the photographs. Check the shared-library view as well. Apple states that other participants can no longer see these items in the shared library once they have moved back.

Treat shared deletion as a different decision

All participants can delete items in the shared collection. Apple specifically warns that deleting a photograph you added does not leave a copy in your personal library. The move-back command is the documented choice when keeping your own item is the goal.

Before a substantial withdrawal, coordinate with the people who rely on the collection. Removing shared access does not establish that nobody previously exported a copy, so describe the outcome accurately as a change to the shared library.

Keep an independent backup of important media and verify the moved selection before proceeding with more photographs. If the actual goal is leaving or deleting the entire shared library, review Apple’s separate membership procedure first; that has broader consequences than returning a selected set of your own contributions.

References: Apple: removing shared-library photos, Apple: shared-library setup and membership.