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In the imposing mountains of Tibet, nomadic yak herdsmen still make an annual 45-day trek to gather salt, to satisfy dietary and ritual needs. Ethnographer and filmmaker Ulrike Koch’s The Saltmen of Tibet examines this ancient tradition, emphasizing the salt-gatherers’ spirituality and the remote landscape’s grandeur. Koch also contrasts the threatened tradition with the techniques of the newly arrived Chinese, who built roads into the region so they could truck the salt away. Saltmen screens at 8 p.m. tonight and Friday at the Hirshhorn Museum & Sculpture Garden’s Ring Auditorium, 7th & Independence Ave. SW. Free. (202) 357-2700. (Mark Jenkins)