Final answer:
A cross-fade is a transition technique often used in film and theater to smoothly transition between two scenes or lighting effects.
Step-by-step explanation:
When one set of lights comes down at the same time that another set of lights come up, this is known as a cross-fade. A cross-fade is a transition technique often used in film and theater to smoothly transition between two scenes or lighting effects. It involves gradually fading out one set of lights while simultaneously fading in another set of lights, creating a seamless transition.