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Changing Slides

By Henry Petroski

Six or seven years ago, few students in my classes used PowerPoint for their term project presentations. I certainly did not use it for my lectures.

The pioneers who brought their own laptop usually had to look for a proper cable to hook into the projection system, whose operation was not obvious. Those who brought their presentation on floppy disk often had to load several onto the classroom computer, which took a while. A lot of class time was consumed watching students struggle with technology.

On more than one occasion, a student and the class hacker huddled over a computer while four or five other presentations proceeded using more conventional media, such as overhead transparencies. The student whose files were not loading properly was a nervous wreck by the time all was ready.

Today, virtually all students use PowerPoint effortlessly and their CDs load almost instantaneously. The presentations go like clockwork, many of the students having used the software's Rehearse Timings tool. Though some of the canned slide designs and transitions employed are not to my taste, and bullets often seem overused and misused, overall the presentations are quite effective.

My experience using PowerPoint for my own presentations is limited. Since I have thousands of undigitized 35-mm slides, I still use them when I want to project images of bridges or other structures in class. Most students today are unfamiliar with the once-ubiquitous technology, as is evident when I ask one sitting next to the projector to turn it on or focus it.

These now-quaint projectors were long the butt of running jokes. It seemed that an extension cord was never at hand, and the remote control did not reach to the podium. The audience snickered when slides were upside down or backwards, and groaned when the bulb blew in the middle of a presentation.

Extension cords still seem not to be where they are needed, but PowerPoint is well on its way to making the 35-mm slide projector obsolete. The transition will likely be complete when my generation retires from the classroom and the lecture circuit. However, that is not to say that all aspects of presentations will be uniformly better, as I have learned in creating some new lectures using PowerPoint.

One advantage of the old technology was the ability to intermix horizontal and vertical slide formats. I especially welcomed this, since bridges are essentially horizontal structures, but their towers are vertical. In PowerPoint, every slide must fit the horizontal format of the computer screen. Sure, vertical images can be included, but they necessarily must be reduced in size.

Increasingly, projection screens come in computer-screen proportions, which is perfect for PowerPoint presentations. When one classroom I use was modernized, its old square projection screen was replaced by one in the new format. Now, when I show 35-mm slides I have to reduce the image area to accommodate the verticals, meaning that all of my slides must be projected about 50 percent smaller than they used to be. Students in the back of the lecture room cannot easily see the details to which I refer.

New technologies do have both advantages and disadvantages compared with the old, but on balance the former outweigh the latter. It is certainly more convenient to carry to class or on a lecture tour only a single slim CD containing several PowerPoint presentations rather than bulky carousels or dozens, if not hundreds, of slides that have to be loaded and unloaded before and after each presentation. And the likelihood of slides getting stuck, jumbled, or misorientated is essentially nil when using PowerPoint files.

I doubt that I will add any significant number of new 35-mm slides to my aging collection, though I will likely continue to use those I have, as long as projectors remain available. The thought of digitizing my slide collection is not one I relish, but any new presentations I prepare from scratch will be in PowerPoint. Once again, students have taught their teacher a better way.


Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University.
His latest book is
Small Things Considered: Why There Is No Perfect Design.

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