Eli5: How do photo restoration artists know the supposed colors of greyscale images?

Question

Are the colors based purely on their assumptions/imagination, or do the greyscale images retain some sort of data that tells what color on what part?

In: 641

Answer 1

>do the greyscale images retain some sort of data that tells what color on what part?

Normal pictures don’t, but there’s one important case where it does contain some info.

Early color TV shows sometimes only survived as 16mm b/w film, because the tapes were reused. There’s some interference called “dot crawl”, an artifact of how analog color was transmitted, that also made it onto the b/w copies. From that you can restore the original color.

This restoration method was used on some Dr. Who episodes, and on some other BBC shows that only survived as 16mm b/w prints