In anticipation of the new application Photos This topic is very relevant. In addition, the transfer of old photos on an external hard drive will free up tons of space on the not very roomy MacBook Air or Pro. Below we explain how to do it.
Before you begin the migration we recommend to make a backup in Time Machine, to protect yourself if something goes wrong.
After creating a backup, open the iPhoto application, click "File" and select "Go to the library."
A new window appears with a list of all the libraries of photos. Seeing the desired library or create one in the window, close iPhoto and connect an external hard drive or USB flash drive. disk icon appears on the desktop and in the Finder sidebar. Now open the folder in Finder "Images". There you will see a list of your media libraries.
Drag the icon of the desired library on the hard disk. Now copy your music library stored on an external drive. It remains to prove that iPhoto. Hold down the Option key and click on the iPhoto application icon in the Dock or Applications menu. A window appears with a list of available media libraries. Click "Other Media Library" and select the one you saved on an external drive.
As long as the external drive is connected to your computer, the iPhoto library will see it in the list. Now you can re-open the Finder, navigate to the folder "Images" and delete the library, which you have transferred to an external drive.
And do not forget to empty the trash :)