This CyberKenBlog post tells how to maintain the crispness of your projected images when you zoom in on them in a slideshow or photofilm.
If you pan and zoom your photos when you project them, particularly if you project them very large, as on the wall of a room, you will need high resolution image files. Panning does not adversely affect the quality of an image, but zooming sometimes does.
Here are several ways to ensure that your photos have a high enough resolution to retain their crispness when zoomed:
Set your camera to take large image files.
RAW images fit this bill, or fine JPEG images (those least compressed). When you save your images after editing them, do not downsize them. Keep their original dimensions.
Use your best lenses.
Some lenses have a higher resolving power than others. Keep a record of which images you take with which lenses, then examine the quality of your shots by viewing them in a pan-and-zoom slideshow. (The new Flickr.com site shows your photos in super high resolution and full screen.) This will help you identify your best lenses. In general, macro lenses are ground with greater precision, and therefore are optically superior; and many can be used for purposes other than closeup photography.
Use ISO 50 films for projecting.
These have very fine grain, so when you zoom in there is little change in the crispness of your images. For color images I find Fujifilm’s Velvia 50 very suitable, and for black and white shots, Ilford Pan-F 50. If you need a faster black and white film with very fine grain try Ilford XP2. It is rated at 400, but you can expose frames at 800 on the same roll because of its wide exposure latitude. XP2 is processed like color print film, so even some drugstores can develop your negatives, another great advantage!
To see that a set of my street photography in full screen, pan and zoom mode, go to: http://www.flickr.com/photos/tcd123/sets/72157624060796786/ and click on the slideshow button at the top left of the page.