Beyond the basic explanation of "blue screen", have you ever wondered how they used removed the blue from a background. These days compositing software makes it simple to select a colour and make it transparent, but before After Effects and similar compositing software existed, the entire process was done optically with physical film strips, lights and cameras.
Join me in a deep dive as I share with you what I've discovered about the labour intensive process involved. By the end of the video, I hope you'll be as awed as I am over the lengths companies like Industrial Light & Magic (ILM) went to in order to make cinema magic.
(I also feel that I should point out, the optical printers ILM used were "computer controlled" so that all the frames and timings lined up correctly. Everything was still composited optically.)