June 18, 2012, 5:06 PM — Here's how you can free up disk space by moving your iPhoto Library onto an external hard disk.
1. Be sure that your external hard disk is connected to your computer.
2. Find your iPhoto Library (it should be in your Pictures folder) and then drag and drop it onto your external hard disk. Or use Cut in the Edit menu, then paste it onto your external disk.
3. Be patient while your iPhoto Library is moved to the external disk. If your have a large library, it could take a while.
4. Once the move is complete, hold down the Option key and open the iPhoto Application.
5. A menu will pop up, asking you which library you want to use in iPhoto.
6. Find your iPhoto Library on your external disk, then click the Choose button.
Now iPhoto will remember where your iPhoto Library is and will default to it when you open the application.
For more, see the original article at the link below.
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