When Emmett Till was brutally beaten and murdered in Mississippi in 1955 for flirting with a white woman, his mother had an open-casket funeral so people could see what had been done to him. When Bull Connor turned dogs and firehoses on African Americans in Alabama in 1963, the footage on the evening news shocked a country that had no idea the extent of the violence that was roiling the South.

Filmmaker Ava DuVernay knows the power of images too. The police assault against black marchers on the Edmund Pettus Bridge helped galvanize support for the Voting Rights Act of 1965, thanks in no small part to photographs of the march that appeared in newspapers and weeklies. DuVernay recreated that march in her 2014 film Selma with visceral, violent images of officers on horseback and smoke bombs and blood. It’s both repulsive and solemn, and it’s supposed to be.

In The 13th, DuVernay’s new documentary about the growth of the U.S. prison population over the last half-century, we see disturbing archival photos and video—lynched black men hanging from ropes, Klansmen in white robes, white bullies shoving a black businessman in the street—rather than images of noble speeches and orderly marches that we more comfortably associate with the civil rights movement of the 1950s and ’60s. Racism and oppression are actions as well as concepts, and film is a powerful medium for demonstrating that.

The 13th takes its name from the 13th Amendment to the Constitution, which abolished slavery and involuntary servitude “except as punishment for a crime whereof the party shall have been duly convicted.” The primary argument, made through academics and political figures, is that the growth of the U.S. prison population from 300,000 in 1972 to 2.3 million today is the result of a series of political, policy and business decisions that took advantage—sometimes intentionally, sometimes in the outcome—of African Americans.

The bulk of the film is a chronology of significant events from the 1960s to today, and a recurring motion graphic charts the steady rise of the prison population through the elections. You see the growth line pitch sharply upward in the 1980s, when mandatory minimum sentences, lifetime sentences for third-strike offenses and drug convictions—all of which disproportionately affected black men—spike the prison population from 1.2 million in 1980 to 2 million by 1990. Like the charts showing the rise in temperatures and carbon levels in the climate-change documentary An Inconvenient Truth, the line showing the prison population in The 13th is a constant reminder of a situation getting worse over time.

There is a book’s worth of information packed into the film. With roughly two dozen talking heads in constant rotation, it documents the rise of the Ku Klux Klan in first half of the 20th century, the civil rights movement, the crime wave of the 1960s, Richard Nixon’s Southern Strategy, Ronald Reagan’s drug policies, George H.W. Bush’s Willie Horton ad, Bill Clinton’s 1994 crime bill, Trayvon Martin, #BlackLivesMatter, Barack Obama, Hillary Clinton and Donald Trump. The ushering of evidence is methodical, convincing and at times totally overwhelming.

Like the charts in An Inconvenient Truth, the line showing the prison population in The 13th depicts a situation getting worse over time.

The 13th’s premiere Friday on Netflix is timed for maximum impact. After two years of not a single black actor or filmmaker getting a major-category Oscar nomination, The 13th will be a high-profile contender for Best Documentary. (Duvernay was snubbed two years ago for a Best Director nomination for Selma, which was nominated for Best Picture.) And it is a political film that that will highlight mass incarceration of African Americans a month before a presidential election that has already been one of the most racially polarizing in history.

Near the end of the film, you hear Donald Trump at several rallies this summer making comments about “roughing up” protesters over scenes of a white man at one of those rallies repeatedly shoving a black woman through the crowd and a similar black-and-white archival scene of a mob shoving a black man through the streets. The scenes are uncomfortably similar.

Will The 13th matter? In a fractured media and social-media landscape where cat videos and Netflix and the nightly news are talking over and through and past each other, where there’s no Walter Cronkite to tell us to pay attention, can a film—can anything—rise above the noise?

Judging by this film’s raw materials, yes. Video, perhaps now more than ever, is perhaps the most powerful medium we have to motivate the best (and worst) angels of our nature. The proliferation of smartphones and bodycams and surveillance has dragged many abuses into the light that would otherwise go unnoticed.

And then there’s the platform: The word-of-mouth success of Netflix’s Stranger Things series this summer would suggest that Netflix has the scale and credibility to lift an important film if anyone does.

The 13th’s surveillance footage of prison violence and smartphone videos of the police killings of Eric Garner, Philando Castille and others are hard to watch even if you’ve seen them before. Those scenes remove the distance between you and imminent tragedy, and they evoke something like the empathic response that you would have if you had witnessed those things in person.

That’s reason enough to watch.