system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how movies made in the 1970's, 60's, etc. can be re-released into HD format nowadays? (Like the Star Wars blu-ray super pack)
gpt
Film is analog, so you can't directly compare it to digital resolutions, but the quality that you get on physical film is much much higher than standard definition (SD) and still more than enough for a high definition (HD) picture.

When they put Star Wars onto VHS they reduced the quality of the picture a lot in order to fit it onto the VHS format. When the released it onto DVD they still had to reduce the quality quite a bit, but less than on VHS. Now they're releasing it for Blu-Ray they're still reducing the quality, but a lot less than for DVD.

If you watched it on a film projector, or at the cinema with a modern industrial digital projector (not like at home) the quality would still be higher than Blu-Ray.

Just looked it up. HD is about 2 mega pixels (2 million pixels in each image). Wikipedia says that 35mm film equates to about 20 mega pixels (20 million pixels in each image).