'Starlet' helmer Sean Baker delivers another compassionate portrait of life on the L.A. margins with this big-hearted, low-budget tale of two transgender prostitutes.

Even those who don’t count themselves among the transgender-prostitute-movie-shot-on-an-iPhone demographic will want to try “Tangerine,” an exuberantly raw and up-close portrait of one of Los Angeles’ more distinctive sex-trade subcultures. Centered around two sharply drawn transgender women who find the resilience of their friendship tested and affirmed over the course of one busy Christmas Eve, writer-director Sean Baker’s sun-scorched, street-level snapshot is a work of rueful, matter-of-fact insight and unapologetically wild humor that draws a motley collection of funny, sad and desperate individuals into its protagonists’ orbit. The result is a big-hearted, stripped-down yet technically innovative feature obviously destined for a limited audience (even in the age of Amazon’s very different “Transparent”), but it should be enthusiastically embraced on and beyond the LGBT fest circuit.

Following “Starlet,” his 2012 drama about the unlikely friendship between a 21-year-old aspiring porn actress and an octogenarian woman who missed her own shot at Hollywood celebrity, Baker has once more delivered a tender yet tough-minded look at little-remarked-upon lives in the margins of L.A.’s sprawling sex industry. In terms of style and energy, however, the director has gone in a viscerally exciting new direction. Working again with d.p. Radium Cheung, Baker opted to shoot the entire film on Apple iPhone 5s cameras equipped with brand-new anamorphic adapters, allowing for not only a more intimate, caught-on-the-fly feel, but also a bracingly cinematic widescreen look that takes on an almost radioactive glow in the harsh glare of an L.A. winter. The title, the meaning of which is never explicitly spelled out, could just as well refer to the sizzling orange of the sky that stretches over the characters’ heads.

The action spills out across several seedy, crime-riddled blocks near the intersection of Highland Avenue and Santa Monica Boulevard, an area where johns can get their fix from transitioning male-to-female prostitutes like Alexandra (Mya Taylor) and her best friend, Sin-Dee Rella (Kiki Kitana Rodriguez), whom we first meet hanging out at a doughnut shop that will serve as one of the movie’s key locations.

It’s Christmas Eve, and Sin-Dee has happily just emerged from a 28-day prison stint, but she flies into a rage upon learning that her boyfriend/pimp, Chester (a fine James Ransone, not seen until later), has been two-timing her with a “fish,” vulgar slang for a biological female. Alexandra urges her to forget about it, but Sin-Dee, not for nothing named after a downtrodden fairy-tale heroine, sets out on a quest to track down the other woman, Dinah, and let her and Chester both have it.

And so off they go, with those smartphone cameras in rapid pursuit, tracking their separate paths as they diverge and converge over the course of several hours. Early on, Alexandra decides to abandon Sin-Dee to her own highly impulsive devices, not least because she has a few errands of her own to run — and a few transactions to complete — before her scheduled nightclub performance later that evening. But while she’s ostensibly the mellower, more composed of the two, Alexandra is hardly one to be trifled with: One of “Tangerine’s” funnier sequences shows she’s not afraid to get rough when it comes to dealing with a john who tries to renege on payment. (“You forget I got a d—, too,” she mutters before going in for the kill.) Meanwhile, Sin-Dee eventually lays hands on Dinah (Mickey O’Hagan), yanking her out of a filthy, overcrowded motel-room brothel and then dragging her by the hair across what seems like half of Hollywood, the two of them apparently hellbent on setting a new record for uses of the word “bitch” in a motion picture.

Interspersed with these two threads is the tale of a third character, a middle-aged Armenian-American cab driver named Razmik (Baker regular Karren Karagulian, also an associate producerhere) who spends most of the same afternoon wearily picking up his own series of fares. Razmik’s path will eventually cross with those of Alexandra and Sin-Dee, although exactly how is not immediately apparent. For much of the early going, he seems to be there mainly to break up the narrative monotony, though this also results in a messier, choppier feel to Baker’s editing.

Still, even when it seems to be going nowhere in particular, “Tangerine” teems with the sort of wry, deceptively offhand details that convey an authentically fascinating sense of place — whether it’s the blase attitude of two police officers toward the prostitutes in their midst, with whom they’re practically on a first-name basis, or a man’s irritated realization that the girl he’s picked up doesn’t have the precise equipment he was expecting. (He ejects her from his vehicle with the disgust of someone who can’t believe people don’t know their L.A. street corners.)

Taylor and Rodriguez, real-life friends who were familiar with the area in question, provided significant input on Baker and Chris Bergoch’s screenplay, which drew upon the experiences of several transgender prostitutes whom the four befriended during their collaboration. Yet all that research would amount to little were the first-time thesps not so naturally compelling onscreen, and Baker’s adoration for his two lead characters — their attitude, their saucy colloquialisms, the brassy self-assurance with which they carry themselves — could scarcely be plainer from the way his camera races to keep up with them, while high-energy trap music erupts on the soundtrack in loud, propulsive bursts. (The women’s generally unflashy attire is the work of costume designer, production designer and producer Shih-ching Tsou, who also has a small, pitch-perfect onscreen role.)

Rodriguez is fierce, alert and seemingly always on the move; Sin-Dee’s revenge quest is more than a little exasperating, but you can see why this wild, irrepressible figure would be so irresistible to so many in her midst, even as she stubbornly demands that she and others like her be treated and addressed with respect. Yet it’s Taylor who earns the film’s most affecting moments, particularly a scene where she softly croons to a virtually empty nightclub — in its own way, an apt metaphor for a life of defiant self-expression. And of all the outlandish sex scenes that have flooded Sundance screens so far this year, few are more poignant than a perfectly timed sequence of Alexandra and a regular client going through a car wash, their activity obscured from view by soap, water and automated brushes.

Not to be left out of the filmmakers’ sympathies are Dinah and Razmik (well played by O’Hagan and especially Karagulian), who may not have to deal with the specific stigmas and abuses that plague Alexandra and Sin-Dee on a regular basis, but who turn out to be, if anything, leading even more frustratingly constricted lives. Even when the film’s multiple lines of action converge at an insanely melodramatic climax — voices are raised, insults are thrown, and barriers of every kind are erected and torn down — Baker manages to suggest that all this clashing noise might be a necessary hurdle to a greater level of understanding. It’s this bigger-picture compassion, born of an impulse to place the unique struggles of sexual and ethnic minorities in conversation with each other, that elevates “Tangerine” from a raggedy little group portrait to a generous and surprisingly hopeful vision of humanity.

tangerine001.jpg