Tierney Gearon’s stunning photographs of her children—often in masks or naked—at a London gallery in 2001 led one TV blowhard to deride her work as “exactly the sort of pervy pics that get downloaded from the Internet.” The controversy made Gearon “doubt myself as a mother.” Then—as if moving from Sally Mann to Diane Arbus territory—she started photographing her own mother, a manic-depressive, schizophrenic woman living in upstate New York. In advance of a show here this fall at Yossi Milo gallery, a new documentary at the Tribeca Film Festival, Tierney Gearon: The Mother Project, attempts to answer the questions her photographs raise, beginning with: What does her mother make of this? Mom’s reactions are as varied as her moods, from the victimized (“You’re making me look like I’m crazy!”) to the proud (“Tierney has never taken a picture that wasn’t beautiful”). Gearon continues to worry over her own motivations. “I am not fucking exploiting her—she exploited me her whole life!” she yells in the film. Later, she bursts into tears as she recalls how she left her baby crying alone in the hot sun—just to get the perfect shot.