Why did St Veronica become a patron saint of photographers?

Veronica became the patron saint of photographers because when she purportedly wiped the face of Jesus, his face was imprinted onto her veil.

The story begins with Luke 23:27-31, which tells us that certain women lamented as Jesus carried his cross to Golgotha. At this stage, there is no mention of Veronica or of her wiping Jesus' face. An early medieval story expanded on Luke's brief passage, saying that one of these women used her veil to wipe the face of Jesus which then resulted in a portrait on the cloth (a reproduction of which is now kept as a relic in Saint Peter's basilica in Rome). Her name was given as Veronica (vera + ikon = "true image")

It seems unlikely that the medieval authors, well known for their pious creativity, could have known something that the author of Luke did not know. It is even more unlikely that the woman's name happened to coincide with what she was famous for in this story - wiping Jesus' face and receiving a true image of his face. We can say with some certainty that St. Veronica never lived, but she remains important in Catholic liturgy and her feast day is celebrated on July 12.