Setting
Argentum Antipodes is a historical fantasy setting, in which vampires existed alongside humans secretly until something like the 1930's or 40's, when color film photography became popular. The universe is based on an inversion of the semi-popular idea that vampires don't show up in mirrors because mirrors used to contain silver. So in the Argentum Antipodes universe, vampires can instead only be seen in things containing silver, like silver mirrors and black and white camera film. So once color film was invented and popularized, the masquerade was broken, and vampires were revealed to the public. Tensions between vampires and humans are understandably not great, being seen as monstrous bloodthirsty killers for hundreds of years (and notably having actual bloodthirsty killers among your ranks) does a lot to damage an image. So many vampires are quite invested in keeping their vampirism a secret, and many humans are quite invested in revealing those secrets (after all, it's kind of impossible to know if a vampire is a bloodthirsty killer without first knowing that they're a vampire). So vampire hunters frequently utilize photography in order to reveal vampires, since they won't show up in color photos, but will appear just fine in black and white. And vampires often break into darkrooms to destroy film negatives before they can be developed and reveal their identities as vampires. Most (reasonable) vampire hunters are more akin to detectives, simply discovering who is and isn't a vampire and attempting to determine the perpetrators of vampire-related crimes. Some vigilante vampire hunters do exist, though, but killing off anyone that's a vampire generally causes significantly more problems than it solves, since most vampires are not bad people.