system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can there be any HD videos of WW2, when there wasn't any HD cameras back then?

The other day I noticed a program on t.v called "WW2 in HD" or something along those lines. Now my question is, how can they make HD videos from way back then, if they didn't have HD cameras? Has editing really come that far nowadays?
gpt
"HD", today refers to a digital image that is 1920 pixel wide x 1080 pixels high - this is about a 2MP image. Video from WWII is shot on real analog film - silver halide crystals on film. Analog film does have a "theoretical max resolution" that it can be scanned at, and compared to today's HD picture it's very high. 35mm film is estimated to contain about the equivalent of 25MP of information - or about 6000x4000 pixels. So, a 1080 HD scan of a good 35mm analog film print is still losing about 12x the resolution of the original image (converting a 25MP image to a 2MP image).