In the past, lecturers used flip charts. You may remember the easels with pads of very large sheets of blank paper. Lecturers drew on the pages as they spoke, and the pages were more of a distraction than an aid.

Later presentations benefited from slide projectors. They had carousels filled with small slides with text. In the past these were used for family pictures from a simcha. The familiar clickCLICK sound meant that the speaker was moving to the next slide (unless it got jammed in the projector).

Transparencies and overhead projectors were a major advance. Speakers were able to place a slide on a lighted table and project it on a screen. The image was not always sharp, and the best entertainment of the evening was watching the speaker fumble with the slides. Nobody ever seemed to know which direction to place them on the lighted table. The best part came when some of the slippery slides fell on the floor and got shuffled.

However, when the transparencies worked well, the speaker would be able to place more than one slide on the screen. The initial slide had the first part of a concept, and he would then build forther parts of the concept by adding slides on top of that one. Light would shine through all of the slides on the table, and the final build included all of the features of that set. It was rather good for developing a concept.

Today's slide shows do the same thing, but with a computer (and sometimes a computer projector). The build has been improved, with fades for preceding slides, and sound and animation were added. However, the basic concept remains the same. It's like using transparencies without the fumble.

However, those projectors are expensive. That leads to a basic question:

Which is better?