CANNES - If any critics were about to ding Mike Leigh for wading into the warm waters of the period prestige picture for his latest, long-contemplated feature, let it be known that the veteran writer-director has come prepared. "What is wrong with being a portrait painter?" asks a slighted practitioner of the form at an ego-crammed artists' gathering midway through "Mr. Turner," Leigh's expansive, exquisitely realized biography of Britain's foremost Romantic painter. The retort from a colleague is airy and sneery and entirely predictable: "What does it do to elevate the art?" he smugs. 

You might ask the same question, and receive the same answer, about the biopic genre -- routinely dismissed by highbrow critics as an easy-access route to bland, Oscar-gilded gravitas, subverted only by a few filmmakers resourceful enough to bend the form's rigid structure and insert something of themselves between the factual lines. Leigh earned his stripes as an exception with 1999's jubilant "Topsy-Turvy," which used a brief stage in the lives of musical theater giants Gilbert & Sullivan as a jumping-off point for a playful rumination on the trials and errors of creative collaboration.

In taking on the life of J.M.W. Turner, a very different, arguably more enduring contributor to the country's cultural fabric, Leigh is working on a grander canvas, seeing his subject through from his prime (professionally, if not personally) to his decayed deathbed. At 150 unhurried minutes, it's actually shorter than "Topsy-Turvy," but feels more muscular -- a sober affair, though often a mournfully funny one. And while the films cover some common thematic ground -- the artist's insecurity, the tension between pleasing oneself and an audience -- "Mr. Turner's" passions and neuroses feel more peculiar to Leigh and his own work. It's tempting, even, to view the film as biopic-as-self-portrait, revealing shades of one life through another. Leigh has a reputation for prickliness and resistance to self-explication; perhaps it's not surprising that he's long been fascinated by Turner's allegedly gruff, taciturn genius.

As played by Timothy Spall -- an erstwhile mainstay in Leigh's company now collaborating with the director for the first time in 12 years -- Turner could hardly be a more abstruse, less lovable figure. His weatherbeaten face fixed in a pout of sturgeon-like severity, Spall delivers his spare dialogue in a guttural, rumbling register that practically requires subtitles, whittling entire sentences' worth of information down to a single, pointed grunt. He weeps like a sea lion and shags like a rutting rhinoceros; when he coughs, which is often, his phlegm lands practically wet on the screen. It's a boldly animalistic performance, and one that will alienate any admirers who have previously imagined Turner as a figure rendered in his own rapturous brushstrokes. He is the beast to his art's beauty.

Guy Lodge is a South African-born critic and sometime screenwriter. In addition to his work at In Contention, he is a freelance contributor to Variety, Time Out, Empire and The Guardian. He lives well beyond his means in London.