system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can black and white footage be colourised?

I’m probably a brainless jacket potato asking this question but it has always intrigued me. Recently there was some footage posted with an old lady making thread or something and I’ve seen the footage get upscaled and colourised etc and I’m wondering how, if the footage is black and white, it can be transformed.

Side note:

Thank you all so much for your answers and comments! Also a massive thank you for my first ever award! Very much appreciated honestly 🙂 This really lends perspective on how much work people put in to colourising old videos!

Side note 2.0:

Thank you for the second award! Never thought that my curiosity would net me all this information or awards! You guys are all champs 💪🏻
gpt
If you're assuming its computerized you should know its main done by human artists. The artist makes reasonable assumptions about what color a particular object is and then uses the brightness information that the photo has.

In some cases you might find works where a machine learning models was been trained to make a best effort.