Over the course of my years as a graduate student and postdoc in Biology, I've had to give numerous research seminars using Powerpoint. The bulk of these presentations consist of light and electron micrographs. The former comprise both 8-bit color .jpg and .tif files ranging in size from roughly 1200 x 1600 to 1800 x 2400 or so. The electron micrographs are all 8-bit grayscale .tif images ranging in size from 1024 x 1184 (Hey, what do you want for only $800,000!?) to 1920 x 2560.
After a few encounters with some horrible quality digital projectors, I gave up on spending much time tweaking my images. There really is no point spending hours in Photoshop on your images, if you're going to get stuck with some piece of crap video projector that is going to give you horrible results. Even in some recent presentations, I will admit to using Powerpoint's native tools for adjusting contrast, brightness, and even resampling. Really, given the variability in projectors, there really is not much point in even using Photoshop for these basic adjustments. Even using these crude techniques, some of my recent presentations have looked really good, as I've been lucky enough to be able to reserve a projector that I like...
But aside from making basic image adjustments such as these, I've always wondered about how the images should be sized for on-screen shows. I know about printing at 300 dpi, or close, but what should I be doing for an on-screen show? I usually convert tiffs to .jpgs to cut down on filesize; I don't think the difference is really noticeable on screen provided one uses high quality .jpg settings. But what should my target size be in pixel dimensions? Should I leave resolution at 72 dpi? Do these settings differ between Powerpoint and just showing photos using Windows Picture and Fax viewer? I would guess the size of the screen matters, but often I don't know how large my venue is until I get there!
Any help would be greatly appreciated.
Thanks,
Kevin