Until now, the case of Mr. Wangchen, 35, has received little attention abroad. Uneducated and plainspoken, he was an itinerant businessman until October 2007, when he bought a small video camera and began traveling the Tibetan plateau interviewing monks, yak herders and students about their lives.

Tsetring Gyaljong, a cousin who helped him make the documentary, said that Mr. Wangchen’s political awareness was sharpened nearly a decade ago, when he witnessed a demonstration in Lhasa, the Tibetan capital, that was quickly broken up by public security officers.

Image Dhondup Wangchen, who interviewed Tibetans for his film, “Leaving Fear Behind,” has been detained since March 2008. Credit... Still from “Leaving Fear Behind”

“He saw how it was dissolved in two or three minutes and how everyone was taken away,” said Mr. Gyaljong, speaking from Switzerland, where he has lived in exile since escaping from Tibet. “There were no pictures, no testimonies, and he felt like the world should know that Tibetans, despite the Chinese portrayals, are not a happy people.”

Out of 40 hours of footage and 108 interviews came “Leaving Fear Behind,” a 25-minute documentary that is an unadorned indictment of the Chinese government. Although given the choice to conceal their identities, most of his subjects spoke uncloaked and freely expressed their disdain for the Han Chinese migrants who are flooding the region and their love for the Dalai Lama, who has lived in exile since 1959.

In his own comments at the start of the film, Mr. Wangchen said the approach of the 2008 Olympics had compelled him to record the feelings of Tibetans, many of whom were less than enthusiastic about the decision to hold the Games in Beijing.

“We have no independence or freedom, so Tibetans have no reason to celebrate,” said one young woman standing by a road. “The Chinese have independence and freedom, so this is something they can celebrate.”