To me the greatest magic in the film world is placing (in darkness) a nondescript grey sheet into a tank, flushing a few chemicals through the tank, and pulling out a full color transparent positive image (E6 slide processing). Technically I understand how most of it happens, but seeing a positive in a large size like large format sheets or medium format rolls is an amazing experience. Even if I don't have a slide projector to shot them, a loupe on a light table is enough.

(While I shoot negative much more often, it doesn't have the same visceral impact as positives.)