Dear Wikiwand AI, let's keep it short, summarize this topic like I'm... Ten years old or a College student
Photochrom, Fotochrom, Photochrome or the Aäc process is a process for producing colorized images from a single black-and-white photographic negative via the direct photographic transfer of the negative onto lithographic printing plates. The process is a photographic variant of chromolithography (color lithography). Because no color information was preserved in the photographic process, the photographer would make detailed notes on the colors within the scene and use the notes to hand paint the negative before transferring the image through colored gels onto the printing plates.