Originally Posted by Greg Boston
Which takes us to our next piece of trivia, the slide projector. I remember corporate presentations in the late 70's early 80's that used racks of slide projectors all aimed at the same place. By turning one on while the previous one was shutting off, you got a nice cross dissolve.
I still have a dissolve unit. My current configuration only controls two projectors but this particular unit has (had?) add-ons allowing it to go up to 9 projectors at a time. This one is programmable but the previous versions I had were programmed LIVE. You mess up, you start over! You could get anywhere from a cut to a dissolve of several seconds. Interestingly, you could also have one projector hold while the other projector changed several times allowing a constant background over several slides. Then you hit the reset button and all projectors return to the starting position.