When you use the Optimize Mac Storage preference in Photos, full-resolution pictures are stored in iCloud and space-saving optimized copies are kept on your Mac. If you turn off iCloud Photo Library, you'll see two options:
- Download a copy of your iCloud Photo Library to your Mac
- Remove the lower-resolution images from your Mac
If you choose the second option—and the only copy of a photo used in your Faces album or in a Project is a lower-resolution image—the photo may be missing from Faces or Projects.
Before you turn off iCloud Photo Library
You can avoid this issue by downloading all your original pictures and videos from iCloud Photo Library to your Mac before turning iCloud Photo Library off. Follow these steps:
- Open Photos.
- From the Photos menu bar, choose Photos > Preferences
- In the preferences window, select the iCloud tab.
- Select Download Originals to this Mac.
Note: Downloading all your original pictures and videos to your Mac may require significant disk space. Make sure the disk your Photos library is stored on has plenty of space for your entire collection of originals.
If you don't want to download all your originals, you can also download pictures individually off iCloud Photo Library with these steps:
- Go to the Photos tab or the All Photos album and find the picture you want to keep in your Faces album or a Project.
- Double-click the picture's thumbnail to bring the picture into 1-up (full-window) view.
This will download the full-resolution version of the picture to your Mac, making it available in the media browser, your Faces album, and Projects. Repeat the steps for each picture you want to remain available, then turn off iCloud Photo Library.
After you turn off iCloud Photo Library
If you’ve already turned off iCloud Photo Library, you can import a full-resolution copy of the missing pictures into Photos and manually re-add them to Faces (by tagging the face names) or to Projects.