J.M.W. Turner exhibit at J. Paul Getty Museum tosses convention

There’s a moment in “Mr. Turner,” the captivating Mike Leigh movie about the last years in the life of audacious British painter J.M.W. Turner, when the artist is having a heated discussion at the same time that he’s busily painting a picture. Concentration ricochets back and forth between canvas and conversation, like a furious ping-pong game.

Turner (Timothy Spall), agitated and sputtering, suddenly turns and spits on the canvas, rubbing the saliva into fresh, wet paint with his thumb. Without skipping a beat, he resumes with brush and palette knife.

“Mr. Turner” is the most convincing cinematic portrayal of an artist since “Basquiat” nearly 20 years ago. Leigh, like the earlier film’s director, artist Julian Schnabel, understands that when it comes to making worthwhile art, the only workable attitude is: Do whatever it takes.

In Victorian England, the likes of an Edwin Henry Landseer or John Frederick Lewis were not about to go spitting on their paintings. Regardless of the charms of their animal and landscape pictures, they were hemmed in by allegiance to the academic conventions of their day. At the J. Paul Getty Museum, the smartly titled exhibition “J.M.W. Turner: Painting Set Free” reveals why he, not Landseer or Lewis or the rest of the Royal Academy, matters most.

Not unlike the artist, it does so by chucking settled academic convention. The usual take on Turner, which is that he’s great because he anticipated later triumphs in Modern art, is pitched overboard.

The Getty show, opening Tuesday, features 35 oil paintings and 27 watercolors made between 1835, when the artist turned 60, and his death 16 years later. (He was in poor health for much of the time, although he traveled widely.) Jointly organized with London’s Tate Britain museum, where it was seen last fall, and San Francisco’s de Young Museum, where it travels in June, the exhibition is — remarkably enough — a first: According to the fine catalog by curators Sam Smiles, David Blayney Brown and Amy Concannon, there has never before been a museum show focused specifically on Turner’s late career.

Those are the years when he became the artist we know and most admire today.

Interest in Turner has come in waves over the past 150 years. The late work’s atmospheric, luminescent veils of color — often bordering on a mid-19th century eruption of total abstraction — have driven much of the curiosity.

The most recent wave arose from the near-universal acclaim now afforded to perceptually grounded Light and Space art, which emerged in 1960s Los Angeles with such artists as Doug Wheeler and Robert Irwin. Today it extends to artists as diverse as British sculptor Anish Kapoor, whose recent work is currently at Regen Projects gallery in Los Angeles, and Danish Icelandic installation artist Olafur Eliasson.

Indeed, photographs of the blazing artificial sun Eliasson made for his famous “Weather Project,” which packed the crowds into London’s Tate Modern museum in 2003, could almost be pictures of “Regulus,” one of the Getty show’s final works. Turner’s painting refers to the story of a failed Roman general whose punishment was to have his eyelids sliced off, condemning him to a life possible only in darkness.

The picture is like a rendering of a nuclear reactor’s core. It radiates blinding sunlight, which blares between imposing classical buildings and dissolves the heavy masonry into shimmering, evanescent illumination.

Yet it isn’t merely the anticipation of “Weather Project” that makes “Regulus” so remarkable. Instead, it’s a brilliant example of how Turner transformed contemporary history painting. That’s the kind of art the Royal Academy held in highest esteem, partly because approved stories of past grandeur offered narrative explanations for the legitimacy of its own present-day power.

Turner did something different. Rather than tell the ancient story as other history painters might, complete with ponderous hierarchies of appropriate compositional gravity and approved techniques for skillful drawing, he chose radical technique.

Thinly glazed and thickly clotted layers of paint — including pigments suspended in light-diffusing wax, then glazed again — create a turbulent and uneasy visual experience. Turner doesn’t describe Regulus’ fate; instead, he imagines being in Regulus’ shoes: You stare directly into an engulfing blast of opalescent white-gold light, which seems to swallow up the world.

Turner’s genius for using color as a tool for dramatic perspective was, indeed, greatly admired by a subsequent generation of Impressionist painters. It was also seen as a profound precedent for the colorist wing of New York School painters in the 1950s, most notably Mark Rothko.

Yet, the legacy of Impressionism, Abstract Expressionism and Light and Space art has obscured just how much Turner was a creature of his own Victorian era, wrestling with its demands and untapped possibilities. Britain was exploding, the population nearly doubling during Turner’s lifetime, and tumult was the order of the day. He plugged into the adventure in a way no other British artist did.

The Getty exhibition is organized thematically rather than chronologically. Mostly the effort is successful. It shows Turner working through current subjects and pressing ideas, rather than looking toward some imagined future in Paris, New York and L.A.

Take his wild whaling pictures. Yes, they engage the time-honored subject of humanity’s struggle with the elements. But it’s no coincidence that a steady supply of whale oil was essential to the new street lamps illuminating — and, therefore, suddenly modernizing — London. Turner sought the same for art.

Just how committed he was to cementing his project into public consciousness is represented by the famous bequest of nearly 300 paintings and more than 19,000 works on paper he made to England. (By then he was hugely rich, as successful as any Young British Artist today.) All but 13 of the show’s 62 works come from that gift, now housed in Tate Britain.

Disappointingly, though, perhaps the greatest of these did not travel with the show. The textbook picture “Rain, Steam and Speed — The Great Western Railway” (1844) shows a brawny train crashing through a storm. Almost totally abstract, the powerful visual essay on the unnerving clash between England’s rowdy new industrialization and its established pastoral identity is greatly missed.

Among the works not from Tate are the Getty’s own terrific Turners, both now given magnificent context. One is a churning sailing picture. It embodies the artist’s deep affection for Dutch marine paintings.

The other is “Modern Rome — Campo Vaccino” (1839), a masterpiece the Getty acquired four years ago and that had been on loan for decades to the National Galleries of Scotland. Turner’s often experimental use of materials, including his fondness for wax, made his paintings fragile, and many are veined with cracks. Not “Modern Rome,” which is pristine.

Reunited with its pendant, an imagined scene of ancient Rome, the modern view shows the city as layered time — pagan and Imperial antiquity, the Christian Baroque era and daily life as he remembered it from his most recent visit to Italy a decade earlier. All co-exist.

Rome, for artists of Turner’s day, represented the wellspring of small-R republican virtue: Civic standards for the present should arise from an informed discourse with history. That’s a concept long since plowed under in our relentlessly forward-charging world.

But civitas melts into Turner’s layered atmosphere of colored light. The strata of human experience are held within the brilliance of a work of art.

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“J.M.W. Turner: Painting Set Free”

Where: J. Paul Getty Museum, 1200 Getty Center Drive, Brentwood

When: Through May 24; closed Monday

Info: (310) 440-7300, www.getty.ed