What's the best resolution for images in PowerPoint screen shows?
This applies only to presentations that will be shown on screen or projected. The rules are different and a bit more complex if you need to print your slides. If you follow this advice, your images will also look fine when printed at small to moderate sizes, but they'll be too low-rez to allow you to make really nice-looking large printouts.
Making images look good on screen
For images that fill the slide, the image size (in pixels) should be equal to the resolution of the device (screen or projector) on which they'll be shown, plus a "safety margin" to give PowerPoint a little extra data to work with.
For example, assume your computer is set to a display size of 1024 x 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, then it should be 1024/2 or 512 pixels wide and 768/2 or 384 pixels high. (Plus a safety margin).
Tip: Quick Calculation of image sizes
If you know roughly the size you want an image to be on the PowerPoint slide, here's how you can calculate the optimum image size:
- Draw a rectangle of that size.
- Double-click it to display the Formatting dialog box.
- Click the Size tab of the Formatting dialog box.
- Note the height and width of the rectangle in inches (if your system displays dimensions in cm, divide them by 2.5 to get inches).
- Multiply these dimensions by 110 to get the size in pixels to make your image.
But what if I'm projecting onto a really really big screen?
If the show will be projected with a video projector (data projector, beamer), it doesn't matter how large or small the screen is. You're optically magnifying the same image to various sizes, but the number of dots/pixels is the same, so you don't need to change the image sizes, no matter how large or small the screen.
You'll want to set the computer's display resolution to the projector's maximum (usually 1024x768) so base your image size calculations on that.
But what about DPI?
In case somebody tells you things about DPI, ignore them. They're misguided.
In this particular situation, DPI s irrelevant, confusing, meaningless, misleading and assuredly useless information.
All that matters is pixels.
What's the best image format?
Stick with PNG or JPG images.
If the PowerPoint presentation's file size isn't a big issue, use PNG.
If you need to minimize file size (if the presentation will be emailed, for example), use JPG (and do a little testing to see how much compression you can use without harming your images).