There are two ways to use a second screen when presenting your slideshow:
Video mirroring displays the slideshow identically on both screens.
Dual displays allow you to show presenter information or prompts—for example, your slide notes, a preview of the next slide, and a timer—on one screen, while viewers see only the slideshow on the other.
Some notebook computers have video mirroring built in. If yours doesn’t, you must configure it. Other notebook computers may not support video mirroring at all.
Connect the second display or projector according to the instructions that came with the display or projector and the instructions that came with your computer.
See Tips for Using an External Display for some setup recommendations.
Choose Apple menu > System Preferences, and then click Displays.
Click Arrangement and follow the onscreen instructions.
If there is no Arrange button, your computer doesn’t detect the second display.
Make sure Mirror Displays is not selected.
Choose Keynote > Preferences and then click Slideshow.
Select “Present on primary display” or “Present on secondary display.”
The primary display is the one on which you see the menu bar. If you choose “Present on secondary display,” you can customize what the presenter sees on the primary display. See Customizing the Presenter Display.
Click Play in the toolbar.
Advance through the presentation by clicking the mouse or pressing the Space bar.
See Controlling a Presentation with the Keyboard for other options.
Attach the second display or projector according to the instructions that came with the display or projector and the instructions that came with your computer.
See Tips for Using an External Display for setup recommendations.
Choose Apple menu > System Preferences, and then click Displays.
Choose a resolution and number of colors.
Use the same settings for both displays.
Click Arrange and select Mirror Displays.
Open the Keynote document and click Play in the toolbar (or choose Play > Play Slideshow).
To advance to the next slide or object build, press the Space bar or click the mouse.
If you see stuttering during playback, you may need to change the screen refresh rate.
Keynote generally plays back very smooth animations. However, if the two displays have different refresh rates, one of the screens may appear to “stutter” because Keynote synchronizes with the refresh rate of only one display. If you’re using Keynote on an iBook, PowerBook, MacBook, MacBook Pro, or MacBook Air with Mac OS X version 10.3.9 or later, Keynote synchronizes with the external display.
Choose Apple menu > System Preferences, and then click Displays.
Choose Display and then choose an option from the Refresh Rate pop-up menu.
To get the best animation quality, use the external display’s preferred screen refresh rate. You can probably find this information in the display’s documentation. If not, try different refresh rates to see which results in the best animation quality. Most liquid-crystal display (LCD) screens have an internal refresh rate of 60 Hz. Most CRT devices don’t have one optimal refresh rate.
If you’re using a desktop computer and two displays, experiment to determine which display is synchronized with Keynote.
For tips on how to get the best playback using an external display, see Tips for Using an External Display.