Filmed entirely on an iPhone 5s, Sean Baker’s “Tangerine” is an exuberantly raw and up-close portrait of Los Angeles’ underground subculture, centered on two sharply-drawn transgender women who find the resilience of their friendship tested and affirmed over the course of one madcap Christmas Eve. Sin-Dee is back working the streets with her bestie Alexandra after a month-long stint in prison. When Alexandra drops the news that Sin-Dee’s boyfriend/pimp has been cheating on her with a cisgender woman, the two set off on a wild ride through LA, filled with sassy repartee, nightclub debuts, richly detailed characters, and capital D-RAMA. Refreshingly hilarious and full of surprises, “Tangerine” is one of the most buzzed about films of the summer.