104. Select a Screensaver  BEFORE YOU BEGIN 103 Change Your Desktop Picture
 SEE ALSO 123 Set the Computer's Sleep Time 46 Share a Slideshow Screensaver
Some traditions die hard. Back in the early days of high-resolution color monitors, the concept of a "screensaver" was popularized with the After Dark package, the first widespread piece of software designed to save your monitor from "burn-in" effects resulting from leaving it turned on and showing the same image for hours at a stretch. Simple floating logos and starfields, and goofy animated scenes such as flying toasters, kept the screen from ever showing the same thing from one moment to the next when not in use, lengthening the monitor's useful life. As computing power increased, screensavers became more and more lavish, until the present day, where now our idle monitors show fish tanks that are all but indistinguishable from the real thing, crunch numbers in a distributed effort to find intelligent life in space, and download ads for you to read when you come back to your computer after lunch . Monitor technology has come a long way since the first screensavers; not just LCD screens, but even the latest CRT monitors are highly resistant to burn-in effects. Screensavers are thus an outdated concept, except for the small fact that they're cool . Whether the image on your monitor needs to be kept in motion or not, it's hard to resist configuring a flashy display for your computer to show when you're not in front of it. It doesn't hurt that the screensavers that come with Mac OS X are some of the best and most visually pleasing examples of the craft ever yet produced. 104. Select a Screensaver 
| 1. | Open the Desktop & Screen Saver Preferences
Open the System Preferences application (under the Apple menu); click the Desktop & Screen Saver icon to open the Desktop & Screen Saver Preferences pane. The Desktop tab opens by default; click the Screen Saver tab.
| | 2. | Select a Screensaver Choose a screensaver from the Screen Savers list on the left. The choices range from the simple Computer Name (which displays an Apple logo and the computer's name in various places around the screen) to the beautiful Abstract, Beach, Cosmos , and Forest slideshows and the new additions Nature Patterns and Paper Shadow ; an automatically updating three-dimensional RSS Visualizer ticker that can be customized to show the headlines from any RSS feed; the understated rolling colors of Spectrum ; and the mesmerizing Flurry . When you click any screensaver in the list, a preview of it appears in the Preview panel on the right.  TIP Many third-party developers have published their own screensavers for Mac OS X; you can add these to your system by moving them (each screensaver has the extension .saver on its filename) into the Screen Savers folder inside the Library folder in your Home folder. If you don't have a Screen Savers folder inside your Library , create it. After moving the .saver files into the Screen Savers folder, go back to the Desktop & Screen Saver Preferences window; the new screensavers should appear in the list. | | 3. | Configure the Screensaver
Most screensavers have several controls and options you can adjust. Click Options to open these controls in a sheet; click OK when you're done. Generally speaking, because these options don't affect anything but how the screensaver behaves, you can feel perfectly free to tweak any of them however you want. In the case of the RSS Visualizer screensaver, the list of available RSS feeds is defined by what feeds Safari knows about; add RSS feeds to your Safari bookmarks to make them available to the screensaver. See 62 Browse and Organize RSS Feeds to learn more about RSS feeds.
| | 4. | Make Your Own Slideshow Screensaver
If you like the bundled slideshow screensavers ( Forest and Beach and so on) but you get tired of the same old pictures, you can easily create your own slideshows that work just like them. Mac OS X can automatically create a slideshow screensaver from any folder full of picture files.
Select Choose Folder from the Screen Savers list and then navigate to the folder containing the pictures you want to use. Click Choose when the folder you want is selected. All the pictures in that folder now become part of a smoothly cross-fading and panning slideshow, subject to the options you select in the Options sheet.
At the bottom of the Screen Savers list are entries for your iPhoto Library and Last Roll , which let you create slideshow screensavers from your iPhoto Library, just as you can do from the Desktop tab (see 103 Change Your Desktop Picture ). Also as in the Desktop tab, additional iPhoto albums that you create appear in the list below these entries.
| | 5. | Test the Screensaver
To see how the screensaver will look using the full screen, click Test . Don't move the mouse after clicking the button; moving the mouse or pressing a key quits the screensaver and returns you to whatever screen was active before the screensaver kicked in.
| | 6. | Select an Activation Time
You can have the screensaver activate automatically after a specified period of keyboard or mouse inactivity, from three minutes up to two hours (or never). Drag the slider to select the time period that must elapse before the selected screensaver is activated, or drag it to Never to prevent the screensaver from ever activating.
| | 7. | Set Active Screen Corners You can configure Active Screen Corners to allow you to start the screensaver immediately, or to prevent the screensaver from activating while you're not moving the mouse or typing (for instance, if you're watching a long QuickTime movie). Click the Hot Corners button; use the sheet that appears to define what happens when you move the mouse into each corner of the screen. You can configure some corners to activate Expos functions (see 6 Grab the Window You Want ) and other corners to control the screensaver. KEY TERMS Active Screen Corners Also known as "Hot Corners," this feature allows you to trigger certain functions by moving the mouse pointer into different corners of the screen. Such functions include starting the screensaver or invoking Expos . Expos A feature that allows you to shrink all your windows so that they all fit on the screen, so you can immediately click to choose the window you want. | | 8. | Require a Password to Exit the Screensaver
To protect your computer from the prying eyes of people who walk by after your screensaver has kicked in, you can tell Mac OS X not to allow anybody to reactivate the computer unless they type your account password (see 121 Change a User 's Password for information on how to manage the account password, which is what a user enters to start a Mac OS X login session). To do this, go to the Security Preferences pane (click Security in the System Preferences application). Select the Require password to wake this computer from sleep or screen saver check box.
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