As police tear gas rained down on student protesters, Chan Tsz-woon grabbed his Canon 50D camera and raced to the frontline.

It was the night of 28 September 2014 and, as the umbrella movement protests erupted on the streets of Hong Kong, the young filmmaker decided it was his mission to make a visual record of the historic political convulsion.

“I believe that sometimes words cannot explain everything,” the 29-year-old director says. “Images are needed to convey what civil disobedience really means.”

Over the next 79 days, Chan returned repeatedly to the movement’s two main camps. He followed ordinary protesters, including a teacher and a high school student, and captured frenzied clashes between police and demonstrators.

At one point, recorded in the documentary, the filmmaker himself was embroiled in the violence, when he was hit in the face by a police officer.

The result is Yellowing, a 133-minute documentary which premiered earlier this year at the Hong Kong Independent Film Festival and has also been screened at festivals in Vancouver and Taiwan.

The trailer for Yellowing.

The film takes its name from the colour which came to symbolise Hong Kong’s struggle for democracy. Its Chinese name is Memo of the Troubled Times.

Chan says his film is “an important record” that gives an insider’s view of a watershed moment in the former British colony’s quest for universal suffrage.

The director claims some local media self-censored when covering the movement, failing to report from the perspective of ordinary demonstrators.

“Mainstream media mostly focused on the leadership of the movement and exaggerated violent scenes of protesters,” Chan says. “I think independent film producers have the responsibility to document what mainstream media failed to report on.”

Chan says of the film: ‘I think independent film producers have the responsibility to document what mainstream media failed to report on.’ Photograph: Chan Tsz Woon

But on the eve of the protests’ second anniversary, Chan claims all of Hong Kong’s major cinemas are refusing to show his film, the result, he suspects, of creeping self-censorship as businesses shy away from offending Beijing.

At first Chan says he wondered whether the film had been rejected because it “lacked quality or was it because of its political nature?”

“But after it did well in many film festivals, I think it proved that the film itself is OK.”

Vincent Chui, the artistic director of an independent film organisation that is distributing Yellowing, claims the documentary’s positive reviews would normally have guaranteed it a theatrical release.

But Chui says locals cinemas had repeatedly rebuffed his approaches, without explaining why. “Nobody would tell you the exact reason.”

The producer also suspects Hong Kong’s big-screens are shunning the film because of its political nature but admitted: “There is no way for us to know whether [the cinemas] practiced self-censorship or received direct orders.”

Chan says one explanation for his film’s predicament could be the success of Ten Years, a dystopian feature film which envisaged a bleak future for Hong Kong under greater Chinese control.

In April, Ten Years incurred the wrath of China’s Communist party controlled media after it won the best film prize at the prestigious Hong Kong Film Awards.

Chinese state mouthpiece Global Times blasted the film as a “virus of the mind”. Soon after, it began disappearing from Hong Kong screens.

“It might have become harder [for other politically sensitive films] because the film was so successful that it brought about criticisms from the Chinese state media. As a result, cinemas tend to be more conservative towards this kind of film,” Chan says.

Taking their lead from the makers of Ten Years, Yellowing’s producers are fighting back against the marginalisation of their film by staging “guerrilla screenings” in smaller venues such as school lecture halls and a local museum. But Chui said a large-scale cinema release remained their ultimate goal.

“I don’t want [self-censorship] to become a norm like it is in mainland China. It is not a good phenomenon that viewers have started distinguishing independent movies from the so-called commercial films.”

In an email to The Guardian, one of Hong Kong’s biggest cinema chains, UA Cinemas, said it had not been approached about screening Yellowing and said it would not “perform any political censorship at all”.

Two years after the umbrella movement, Yellowing will appear at the Jihlava International Documentary Film Festival in the Czech Republic next month and has been submitted for the prestigious Taiwan Golden Horse film awards.

Chan says he hopes his work will serve as a monument to the city’s political struggle.

“Hong Kong has changed a lot [since the protests]. Some viewers might have participated in the movement wholeheartedly, but they have not revisited those memories because of the negative emotions related to the movement’s failure,” he says.

“My film might provide them with an opportunity to look back at what happened during the protests so that they can tidy up their thoughts and emotions.”