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Using Photos as Desktop Images and Screen Savers
iPhoto lets you share photos with yourself. Select a photo and choose Share > Set Desktop, and iPhoto replaces the Mac’s desktop with the photo you selected.
If you select multiple photos or an event or album, your desktop image will change as you work, complete with a cross-dissolve effect between images. It’s an iPhoto slide show applied to your desktop.
Another way to turn an iPhoto album or event into a desktop screen saver is to use the Desktop & Screen Saver system preference—choose the album in the Screen Savers list (right).
Warning: Using vacation photos ...