Clarification: Actual footage meaning something that was filmed and not just black backgrounds.
In: Technology
Didn’t they sometimes use glass panes with the credits painted on?
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To add on to what /u/FullMetalDove said, there’s also the process of [optical printing](https://en.m.wikipedia.org/wiki/Optical_printer?wprov=sfla1), which is setup that takes footage of film. You matte out where the credits will go, which leaves the credits area unexposed, rewind the film and shoot the credits again, with the negative space matted out this time.
Many techniques have been used over the years, but one of the oldest is to paint the credits on a clear sheet of plastic, then just put that on top of the existing footage.
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