Posted by John W. Wall on January 31, 2008 at 12:56 PM
I'm wondering what your best practices are for doing a Powerpoint slide show that is going to be projected, not just watched on a monitor.
The basic size of a blank slide page seems to be 7.5 x 10 inches, which leaves a little room for a caption below the picture. The only recommendation I've read about says to make your slide 72 dpi, but I'm wondering to what extent, if any, it would help to make it 300 dpi.
Obviously, if 72 works, that's great because it keeps the overall filesize lower and makes it less desirable to make an unauthorized print from. But I also figure the projector is more important to a good-looking slide show than the dpi of the slide.
The 72 dpi recommendation in PowerPoint is so that text will format properly for printing because text size is based on 'points'.(a 'point is 1/72 inch). Your images can be any dpi you want, since the projector will display them at it's native resolution. Just be sure that your images are sized (in inches) so that they fit on the PowerPoint 'page'.
The two downsides for using high image density and leaving it to Powerpoint to settle the differences are speed and total document size. Lots of big images can really slow down Powerpoint, while it whizzes right along using 72 dpi images. If you have a whole bunch of 300 dpi images, your total presentation can quickly grow beyond a size that can be emailed on slower connections, much less burned to a disc on worst cases.
Hank, what you say is true. Thanks for the additional info. Most of my PowerPoint presentations are instruction related, and thus rely more on text than on images. For a show consisting of many images, a lower resolution will be the best way to go.
-PB
Posted by David Bostedo on January 31, 2008 at 2:57 PM
First, there really isn't much difference between using Powerpoint on a monitor or projector, except that the resolution is probably different (and each pixel when projected is a lot larger of course). Other than that, the quality you get in Powerpoint is always going to depend on how Powerpoint renders your image. Powerpoint is going to resample your images to display what it thinks is the right number of inches, regardless of what the dpi is.
For instance, say that Powerpoint thinks a slide is 8x10 inches, and you've inserted a 4x5 image on the slide. Now assume that the monitor/projector resolution is 1280x1024. Powerpoint (along with the operating system and video card) is going to use an area of 640 pixels wide and 512 pixels high to display the image, regardless of your DPI setting. For various DPI settings it will just do different interpolating/resampling, always using the same screen real estate to display your image.
I would guess (and this is definitely just a guess) that you should probably keep the file dpi high enough to meet or exceed the actual resolution of the projector. So if Powerpoint thinks your slide is 8x10, and the projector resolution is, say, 1024x1280, that would be about 128 dpi. So I'd try to keep your resolution at or above that to avoid too much interpolation by Powerpoint, and too much upsampling by the projector. That's just intuition though - it might not make too much difference. Any chance you could prepare a few slides with, say, 72 dpi, 128 dpi, and 200 dpi, and actually look at the resulting projection?
I've never tried the experiment you suggest David. I've just gone with the advice (perhaps Old Saw?) I received to match your image size to screen resolution with a resolution of 72dpi. Let us know what you find out.
Good advice above. It is also worth mentioning that PowerPoint is not the ideal tool for a photography slide show since it cannot be configured to keep the image's native resolution. For a very small fee you can get something like PicturesToExe that allows you to prepare your slides in Photoshop and will not resize them.
Discussion
6 repliesThe basic size of a blank slide page seems to be 7.5 x 10 inches, which leaves a little room for a caption below the picture. The only recommendation I've read about says to make your slide 72 dpi, but I'm wondering to what extent, if any, it would help to make it 300 dpi.
Obviously, if 72 works, that's great because it keeps the overall filesize lower and makes it less desirable to make an unauthorized print from. But I also figure the projector is more important to a good-looking slide show than the dpi of the slide.
Any tips, ideas, suggestions are welcome.
The 72 dpi recommendation in PowerPoint is so that text will format properly for printing because text size is based on 'points'.(a 'point is 1/72 inch). Your images can be any dpi you want, since the projector will display them at it's native resolution. Just be sure that your images are sized (in inches) so that they fit on the PowerPoint 'page'.
-Preston
-PB
For instance, say that Powerpoint thinks a slide is 8x10 inches, and you've inserted a 4x5 image on the slide. Now assume that the monitor/projector resolution is 1280x1024. Powerpoint (along with the operating system and video card) is going to use an area of 640 pixels wide and 512 pixels high to display the image, regardless of your DPI setting. For various DPI settings it will just do different interpolating/resampling, always using the same screen real estate to display your image.
I would guess (and this is definitely just a guess) that you should probably keep the file dpi high enough to meet or exceed the actual resolution of the projector. So if Powerpoint thinks your slide is 8x10, and the projector resolution is, say, 1024x1280, that would be about 128 dpi. So I'd try to keep your resolution at or above that to avoid too much interpolation by Powerpoint, and too much upsampling by the projector. That's just intuition though - it might not make too much difference. Any chance you could prepare a few slides with, say, 72 dpi, 128 dpi, and 200 dpi, and actually look at the resulting projection?
Guy