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.