New York doesn’t look the same as it used to. That’s either a rueful refrain or a relief, depending on your mood, but it’s true whether you’re talking about the shape of the street 50 years ago or last week.

Still, the city does have a few constants. One is the compulsion to put your name on it. Graffiti wasn’t invented in New York, but that is where it was perfected. In the 1970s, kids from the city’s outer boroughs figured out you could spray-paint subway cars and make your name live forever, tagging in unlit train tunnels and in the process inventing a totally new form of expressionism. Attempts to snuff it out have been constant and unsuccessful.

By now, style writing is an exuberant movement with global reach, its language co-opted by multi-national advertising, the work of its early practitioners as cozy in blue-chip galleries as on Louis Vuitton runways. This isn’t a bad thing, but graffiti’s early spirit, its nihilistic urgency, its bleating demand for recognition, is most at home at street level. It’s part of the texture of New York’s built environment, as familiar and correct as its gothic verticality and past-its-sell-by-date scaffolding. Rather than dereliction, it’s evidence of the city’s health—creative life propelling itself to the surface. When it finally dries up, then you know it’s time to really worry.

When it comes to style writing, the piece is the point. But it’s also the remnant of a performance, the trace of a willful act of self-determination, possibly at decent bodily risk. For obvious reasons, writers shy away from the camera. (Even JR, one of the most-well-known working artists in the world, still feels more comfortable behind dark shades and pseudonymous initials, a holdover from his tagging days.)

This is what makes Blake Kunin’s photography so thrilling. For the better part of the last decade, Kunin has photographed members of the loose but prolific BTM crew at work with startling intimacy. His pictures, collected in the new book Bark at the Moon, memorialize BTM’s conquests in unctuous black and white: a splashy fill-in above the old Essex Street Market visible from across Delancey Street; a massive run of fat declarative letters seen from the Williamsburg Bridge. Bark at the Moon functions as a kind of guidebook, illuminating a hidden part of New York street life, the illicit action that goes on overnight and remains largely unseen while the rest of us sleep.

Writing is largely a solitary activity, done in the pursuit of personal glory—more finesse, more nervy spots. Still, in the style writers’ eco-system, friends are important. In the 70s and 80s, crews such as the Fabulous 5ive and Incredible Bombing Masters worked as cooperative units to achieve masterful pieces that surged along entire trains. Contemporarily, there is the Bronx-based Tats Cru, who work in an ebullient color-field muralism, and IRAK, who tramped around downtown Manhattan in the late 90s and early 2000s with anarchic glee. (Their crew name alluded to their penchant for “racking,” or shoplifting.)

BTM stands for Big Time Mob, a kind of knowing wink at the graffitist’s benign-outlaw status. BTM is in fact big-time, at least in surface coverage—their associates pop up along the West Coast, down the Eastern Seaboard, and in Europe—and their contributions to the form are well known, furious and giddy in equal measure. If not exactly anti-Establishment, their ethos is possessed of a healthy disregard for it. (BTM’s most audacious achievement came in 2012, when Lewy BTM managed to mark an outer ledge of the Brooklyn Bridge—a holy grail for New York writers 119 feet over the East River.)

Kunin’s images of BTM’s affiliates are a devotional project, akin to Martha Cooper and Henry Chalfant’s foundational Subway Art (1984). But where Cooper and Chalfant were concerned with an anthropological taxonomy of the art, Kunin is interested in feeling. He shoots his subjects’ finished output along with affectionate attention to their effort—scaling walls, prowling through the inky city night. His pictures combine a documentarian’s zeal with the smash-and-grab panache of Garry Winogrand, who would have his shutter closed before you noticed the lens in your face. It helps that Kunin is himself a graffitist; that these pictures exist at all is evidence of an insider’s access. But he also knows how to make a throw-up shimmer, how to capture the loping curves of a tag so its elegance appears undeniable.

One image in his book stands out for its absence of these thrills. A picture of an N.Y.P.D. task force painting over a graffitied wall is a canny reminder of the city’s priorities. Every once in a while a mayor makes a show of this sort of thing. It’s an easy target. As the city buckles under crumbling infrastructure, a housing crisis, and berserk rents, clean walls are a frictionless way of reassuring a beleaguered populace.

Clean walls, of course, are also a lie. The city is all friction, messy and stimulating. Graffiti, then, is a public service. It reveals the foolishness of trying to impose order on something irrational, or thinking you can gloss the expression that irrationality provokes.

It’s also a lifeline, what Cay 161 described to Norman Mailer as the “faith of graffiti.” It resists the anonymizing effect of the city. Kunin, too, operates under the art’s directive—making what’s ignored visible. His images give the lie to the New Yorker’s lament that the city is a paler version of what it was. Its wilder self still exists, if you’re awake to it.

Bark at the Moon, by Blake Kunin, is out now

Max Lakin is a New York–based writer