Not the wooden toy on a string, although people are much more familiar with the toy than a yo-yo in theatre. A theatrical yo-yo is a device that moves a Gobo to give the effect of movement on stage that is part of the set design.
Okay, this was another one of those huh? moments, as I had no idea what either term meant until I looked it up on Theatrecrafts - Entertainment Technology Resources. There I found out that a Gobo is a metal plate that has a design etched into it that is then projected by a spotlight. Perhaps the bat that is always projected into the sky by Batman is a Gobo. Anyone know?
This kind of projection is used in theatre to create scenes instead of painting backdrops. This can range from trees and plants, windows, an buildings. Often these images are muted somewhat, giving them a slightly out-of-focus effect, so what is in front of them stands out. It would be great to have that ability to create scenes with lighting in our little theatre, but first we'd have to actually have a space big enough to even build a set. Sigh.... How I dream.
When I was reading about the Gobo, it was interesting to see how some people thought the word originated. One possibility has it that in the early days of Hollywood, when the director of photography wanted to block out daylight he'd tell the crew to "Go Black Out". The crew would then hurry to put up black curtains to block the sun.
In filming for feature film or television, a Gobo has a slightly different role. It is a piece of material used to mask or block light that is placed in front of a lantern. Sometimes it is referred to as a Shadow Mask. When lighting an indoor scene for filming there are lights placed in many areas around the setting and sometimes when the camera angle changes, one of the lights can be in the shot, or too strong for the shot. The director may tell the crew to "Gobo that light" to fix the problem.
This will be the last of my A to Z posts dealing with theatre. I hope you have enjoyed learning more about playwrights and how their work translates to stage as much as I have.