The new James D. McDonnell Hall at Princeton University

If you've ever wondered about the feasibility of using rear-screen projection in a large lecture room, here's a good example. The system allows lots more light on the student desks during video viewing, while still giving true blacks in the images.

The Da-Lite screen company furnished the screen, their largest ever. The picture above is contained in an article by consultant Gary Kayye on the Da-Lite website.

One caution. As the article points out, the ability to crate and ship a seamless sheet of rigid plastic somewhat limits the dimensions of the screen. That means that because the screen can only be of a certain height, the room can't be so deep that a student in the back row can't read the projected text of, say, 80-character-width webpages.

Here are some guidelines for legibility.
If the smallest lower-case text characters, as they appear on the projection screen, are one inch tall, the furthest student with "normal" vision can only be about 30 ft away from the screen.

Now... one-inch-tall lower-case characters use about 2.2 vertical inches per line. Thus an 8ft tall screen (96in.) will only hold about 43 lines of text. If you are a long-time multimedia producer, you probably wouldn't put up that many lines at once. But if you're a casual user who sometimes puts a Time magazine or journal article under the document camera, you'll need to adjust the amount of material viewed to keep the projected character size at one-inch . Remember, one-inch tall characters still only allow the furthest student to be 30 feet away from the screen.

If the text characters are 2 inches tall on the screen, the furthest student can be about 60 feet from the screen, but the number of lines that can be presented drops to 22.

Have a question about classroom design, or a good idea? E-mail: is listed by the National Clearing House for Educational Facilities (NCEF)