I know it's now an old saw but it's amazing how bad google and youtube can be. I just learned the term translight and I wanted a short video example yet I couldn't find one that didn't involve marketing. There must be some such results at youtube but if google's search algos are shit - google and youtube will never give show them to me.
A Translight or Translite is a large illuminated film backing typically used as a backdrop in the film and TV industry. The name of Translite originally came from the black-and-white display film made by the Eastman Kodak Company. Pacific Studios in Los Angeles was the sole producer of Translites from about 1950 until about 1979. Technicians there projected images in a darkroom onto the film in strips, which were then removed and processed by hand in tanks by the darkroom crew.
The strips were seamed with tape; then oil paint was applied to the assembled picture for a tinted color effect. The name gradually was applied to any transparency lit from behind and used as a background picture for feature films or television production. Full-color printing of a Translight was first used on the motion picture One from the Heart.
I found a YouTube link in your post. Here are links to the same video on alternative frontends that protect your privacy: