John Constable's Big Ideas

Case in point: The full-size sketch for "Hadleigh Castle" (1828-29) was in 1935 acquired by Britain's National Gallery under the mistaken impression that it was the final version. Similarly, a 1935-37 canvas historians now believe to be merely a full-size sketch for a never-completed painting, "Stoke-by-Nayland," was once thought to be a finished picture.

It's always useful to compare two related objects, as this show invites us to do, if for no other reason than that it creates a kind of tension. Or, in this case, tensions. One is between the romanticism of Constable's bucolic vistas, which idealize the labors of those toiling in his picturesque mill towns, and the clinical observation -- the cold, hard science-- behind the picture's making.

Another is the tension between classicism and modernism. Derided by such rivals as landscape painter J.M.W. Turner for looking like "whitewash" had dripped on them from a nearby ceiling, Constable's artworks can, in passages, look surprisingly contemporary, even more so when we examine his more freely painted sketches, yet its roots are firmly in the 17th-century tradition of large landscape.

Yes, this is a tightly focused show, but in that tight focus, as curator Kelly notes, lies not just some intriguing tension, but one painter's greatest work.

CONSTABLE'S GREAT LANDSCAPES: THE SIX-FOOT PAINTINGS Through Dec. 31 at the National Gallery of Art, East Building, Fourth Street and Constitution Avenue NW (Metro: Archives/Navy Memorial). 202-737-4215 (TDD: 202-842-6176). http://www.nga.gov. Open Monday-Saturday 10 to 5; Sundays from 11 to 6. Free.

Public programs associated with the exhibition include:

Wednesday at noon Gallery talk: "Constable's Great Landscapes: The Six-Foot Paintings." (Repeated Oct. 13-15, 17 and 19 at noon; Dec. 14 and 22 at noon; Dec. 15, 16 and 20 at 1.) Meet at the East Building Art Information Desk.

Oct. 22 from 1 to 4:30 Symposium: "An Expanding Vision: Constable and the Transformation of Landscape." Scholars of landscape painting present illustrated lectures, followed by a panel discussion. East Building Auditorium.

Nov. 4 from 10 to 5; Nov. 5 from 11 to 6 "Weekend in the English Countryside." Films, music performances and hands-on art-making activities for children accompanied by adults. East Building Mezzanine.

Nov. 5 at 6:30 Concert of music by Vaughan Williams and other English composers. West Building Lecture Hall.

Nov. 23 and 28 at 1; Nov. 30 and Dec. 6 at 11 Gallery talk: "Eighteenth-Century British Portraits and Landscapes." Meet at the East Building Art Information Desk.