By Steve Rindsberg, Microsoft MVP and co-creator of PPTools.
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Microsoft Office PowerPoint® 2003
What resolution should I make my pictures to use in a PowerPoint slide show?
If you've asked this question and gotten answers like "Just scan your images at 96 dpi," I'll have to ask you to push your brain's Restart button. You need to clear your head of all that dpi stuff because for PowerPoint purposes, it's wrong, irrelevant, confusing (choose any three).
Working out the right size for images in PowerPoint is a lot simpler than some people try to make it sound. The Basic Rule is this: For images that fill the slide, the image size (in pixels) should be equal to the video screen's resolution.
For example, if your screen resolution is set to 1024 × 768, that's the size you want your full-slide images to be. If the image occupies only half the width and half the height of the slide, it should be 1024/2 or 512 pixels wide, and 768/2 or 384 pixels high.
Highly detailed images sometimes look better if they're set at a bit higher resolution than The Rule demands. So if you're working with maps or images of text, try the same image at several resolutions—you'll quickly get a feel for what works best. Just don't go overboard; the higher the resolution, the larger the image files; the larger the image files, the larger your PowerPoint files will become, and the slower the images will display. You want your images to be just big enough to look good and not a pixel bigger.
What about video projectors? The screen's bigger. Don't they call for higher resolution images?
Nope. It doesn't matter how large or small the screen is; it's the resolution of the projector that counts, and most of them top out at 1024 × 768. They may spread those pixels out over a larger screen, but the number of pixels stays the same.
OK, so what if I don't know anything about the computer that'll run the presentation?
Have you noticed how often the number 1024 × 768 has come up so far? There's a reason for that. 1024 × 768 is a very common resolution for laptop displays and for video projectors, so it's a good choice when in doubt. The images won't be large enough to slow things down even if your presentation is shown on lower resolution displays. Still, the images will look acceptable on higher resolution setups.
Keep in mind that this advice applies to images in PowerPoint screen shows. It'll also give you good results on most desktop printers. But, for poster printouts, 35mm slides, and other high resolution output, you'll want to start with higher resolution images.
Note: To check your display resolution, right-click the Windows desktop, and then choose Properties. In the Display Properties dialog box, click the Settings tab. There, under Screen Resolution, you'll see the current setting. It'll look something like "1024 × 768," (meaning 1024 pixels wide and 768 pixels high).
About the author: In addition to developing add-ins for PowerPoint and answering brain-teasing questions on the PowerPoint discussion list as a Microsoft MVP, Steve Rindsberg is the CEO of RDP, keeper of a popular PowerPoint FAQ site (The PowerPoint FAQ). He is also co-creator (with fellow PowerPoint MVP Brian Reilly) of the PowerTools add-ins for PowerPoint site (PPTools). A frequent international traveler, Steve creates many a presentation in airplanes in the last 30 minutes of flights.