One of the first things you learn about how movies are put together is that everything is on screen for a reason. Even if a cat wandered into the background, it's there because someone decided to keep it. Usually it's there because of a cinematographer.

"The cinematographer's job is to tell people where to look," says Michael Chapman ("Raging Bull") in "Visions of Light," a gorgeous documentary available for free on YouTube. Consider it an entertaining "Intro to Cinematography," because along with stunning clips of their work, "Visions" includes interviews with dozens of cinematographers (aka directors of photography). They're picture guys but they're great with words, too.

"I found out that I was really responding to light," says Ernest Dickerson, a movie-mad child who became Spike Lee's main cinematographer. He describes his job as "heightening the reality to get the audience to feel a certain way."

The early, silent days of the movies gloried in stylized images, but sound created problems such as immobile cameras, as well as new duties for DPs. The 1930s golden age of movies was not so golden for the cinematographer, whose main job was to make actors look attractive.

"Visions" elaborates on many fun movie tricks: how Bill Butler kept the camera at water level in "Jaws" to create terror, William A. Fraker built tension by keeping an actor just out of view in "Rosemary's Baby," and Conrad Hall noticed that a fake rainstorm made it look like Robert Blake was crying in "In Cold Blood."

Those are all from the late 1960s and early '70s, my favorite era of cinematography. I'm partial to the bars of black and white in '40s noir movies, but I like the naturalism of the '60s and '70s, not only for the look but for how it made performances more natural as actors responded to the greater freedom a lightweight camera and available light gave them. (An exception, unfortunately, is actors of color. As recently as two decades ago, it was common to see them look worse than their white peers because cinematographers, nearly all of whom have been white, didn't take the time to learn how to light other skin tones.)

You won't see classically "beautiful" titles such as "The Wizard of Oz" or "Lawrence of Arabia" on my list of the best-photographed movies. You also won't see comedies, where the cinematographers' job is to keep them bright and sunny. What you see, instead, is a lot of darkness, illuminated by visions of light.

Citizen Kane (1941)

Duh, right? "Citizen Kane" is at the top of every classic movie list. DP Gregg Toland was a full collaborator with writer/director Orson Welles, and his use of deep focus and crazy camera moves practically invented film noir. Few movies stand up to repeat viewing as well as "Kane." Once you get the story down, it's even more rewarding to watch how it comes together.

The Conformist (1970)

It's in color, but Bernardo Bertolucci's classic is all about the play of shadow and light, especially in an odd dancing scene where venetian blinds and a black-and-white dress combine to fool the eye. The drama about the rise of fascism blends tricks from the entire history of movies, and just about all of Vittorio Storaro's images are suitable for framing (he would win Oscars for "Apocalypse Now," "Reds" and "The Last Emperor").

The Godfather (1972) & The Godfather: Part II (1974)

The greatest cinematographer never to win a competitive Oscar? Easy. It's Gordon Willis, whose interest in natural light, even if it made his characters hard to see, freaked out Hollywood execs. Directors loved him, though, which is why he shot not just the "Godfather" trilogy but also "All the President's Men," "Annie Hall" and "The Parallax View." It's difficult to imagine '70s movies without Willis' gritty style. As he says in "Visions," he "pictured things a different way and in some cases it caused a ruckus."

Children of Men (2006)

Emmanuel Lubezki is the only cinematographer to win three Oscars in a row (2014-16 for "Gravity," "Birdman" and "The Revenant"). He should have won one for the single-take car sequence in "Children of Men" alone. Lubezki's work sometimes draws attention to itself, but as in that scene, the showiness is a way of directing us to a pivotal moment where Lubezki's wizardry matches the wonder of what the characters are doing.

Blade Runner (1982)

The downside of the old boys' network that has existed since the beginning of the movies is that it's all boys (the first female cinematographer to earn an Oscar nomination was Rachel Morrison, just two years ago), but one upside is you can trace top talents' careers through their apprenticeships. Jordan Cronenweth, whose noirish, eerily industrial "Blade Runner" is one of our most distinctive-looking movies, assisted Conrad Hall on "In Cold Blood," as did William Fraker.

The Night of the Hunter (1955)

Weirder than anything else hitting theaters in the 1950s, it's no wonder it flopped. It's a stark tale of good and evil (black-and-white was ideal for that), but the presence of silent movie legend Lillian Gish is a dog whistle that "Night" cinematographer Stanley Cortez will draw on bizarre, early-cinema visual techniques to tell the story of an elderly woman who confronts a psycho.

The Man Who Wasn't There (2001)

Frequent Joel and Ethan Coen collaborator Roger Deakins has shot tons of distinctive movies (his "Blade Runner 2049" won him the Oscar that eluded Cronenweth), but working in black-and-white let him try bold things most present-day cinematographers don't get to do. Deakins calls it his most "perfect" film.

Chris Hewitt • 612-673-4367