system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How can films shot in the 80s look amazing in hi-def today?

In honor of the passing of Roddy Piper, I re-watched They Live in HD and the picture was amazing. It looked even better than I remember watching it in the theater, and most definitely better than the many times I watched it on VHS/on cable. How is this possible?
gpt
Movies were historically shot on film; film doesn't really have a "resolution" in the sense of "high definition" what have you. Film is an analog medium, and it holds a LOT of detail. When you watched it on VHS or on TV historically, you were watching a low resolution digital scan of the analog film; when HD technology came around, they rescanned the film at high resolution.

What we now call HD doesn't even capture like a tenth of the actual detail on 35mm film, however. 4K, which is about four times the resolution of HD, only captures about one fourth of the resolution that 35mm can really capture. To get a scan of ALL the detail of 35mm film, you have to go all the way up to about 8K. You can keep scanning past that, but without much additional returned for it.