A Venice view by J.M.W. Turner is expected to earn more than $20 million at Christie’s sale of Old Master Paintings this morning. If it reaches the auction house’s hopes, it will easily rewrite the Turner record at auction – currently at $9 million, for a picture sold in 1984 – and it could even exceed the record for any British picture, currently held by John Constable’s “The Lock,” which sold for $21.1 million in 1990. If so, the painting would account for nearly half the $50 million Christie’s anticipates its Old Masters sale will bring.

Turner painted “Giudecca, La Donna della Salute and San Giorgio” (1841) in London, having executed hundreds of watercolors in Venice. In this oil painting, the lagoon retains the light transparency of a watercolor, while the buildings behind it are built up with white impasto. The painting is light and airy, relative to Turner’s radically dark, deconstructed London scenes.

“I think this is the single greatest work of art I’ve ever personally handled,” Christie’s co-head of Old Master Paintings, Nicholas Hall, said. “It is superbly preserved, by the greatest of all British painters, and is incredibly rare.”

The picture is being sold by the St. Francis of Assisi Foundation, which received it as a donation from a collector. The foundation, incorporated in New York State in 2000, is not to be confused, according to Christie’s, with a similarly named foundation that appeared in news reports in 1999 in connection with a scam perpetrated by disgraced financier Martin Frankel.

The painting is generating substantial interest among British collectors and dealers, as well as among European dealers and American private buyers. “The Turner is fantastic,” Robert Noortman, a Maastricht-based Old Master dealer, said. “It’s more rare than a Rembrandt today.” If a museum bids, Mr. Hall said, it will likely not be a British one: The price tag is too steep, and there are plenty of Turners at the Tate.

Doubling Turner’s previous public price might seem a hardy feat. But the artist’s stature has been growing in recent years, as recent exhibitions have placed him at the forefront of Impressionism. “Turner Whistler Monet” at the Tate Britain last year made clear the impact of Turner’s interpretation of London fog and Venice light on Monet, who painted similar scenes 60 years after the British painter. Indeed, Turner is a transitional figure between Old Masters and Impressionists, and his work lures buyers from both fields. “Turner is a profoundly modern artist,” Mr. Hall said. “There is no reason why this shouldn’t be in a collection with Impressionist or modern works.”

In addition, views of Venice are wildly popular. “At the moment, vedutes, or Italian views, seem to be quite desirable,” the co-director of London’s Simon Dickinson Gallery, David Ker, said. Last year’s highest price at auction was for Canaletto’s “Venice, the Grand Canal,” which sold for $32.5 million at Sotheby’s London in July. Monet’s “Le Grand Canal” (1908) sold for $12.9 million last November at Sotheby’s Impressionist and Modern evening sale in New York. The domed Santa Maria della Salute in Monet’s picture looks like an enlarged, duskier version of the white domes and spires in Turner’s painting.

Though Turner traveled to Venice three times and painted it obsessively over his career, completing hundreds of watercolors and 24 oils, only four other paintings of Venice exist in private hands. “They are among his most beloved paintings,” Mr. Hall said. Critics at the time embraced them, after roundly assailing darker visions such as “The Slave Ship” (1840), now at the Boston Museum of Fine Arts.

Christie’s is breaking with tradition this year by holding its sale of Old Masters paintings in April. Auctionhouse officials say they moved it to better space the auction calendar between the London sales that occur in December and July. But European dealers are not uniformly pleased with their new travel schedule. “It’s a nuisance, having to come twice for the same thing,” Mr. Ker said. “They are taking a bit of a risk.”

Almost anything new is risky within the more courtly tempo of the Old Masters field. In January, Sotheby’s introduced a sale titled “The Dealer’s Eye,” featuring works from dealers’ storerooms. It performed below expectations, with its total of $5 million hitting below the low estimate. Nonetheless, Old Master paintings increasingly look like a good deal as contemporary works take in ever higher sums.

“Savvy people today are realizing you can buy a beautiful little Tuscan School picture for the same price as an ordinary piece of contemporary art,” Mr. Ker said. It remains to be seen how many crossover buyers are actually participating in the sales, but the market is flourishing all around. The $74.8 million Sotheby’s achieved in January for its back-to-back sales of Old Master paintings and drawings was the highest ever for the combined sales in New York.

Christie’s Important Old Master Paintings sale today at 10 a.m. (20 Rockefeller Plaza).

Old Master Highlights

Stefano di Giovanni, called Sassetta, “Saint Augustine, a Pinnacle of the Borgo Sansepolcro Altarpiece” (1444). Estimate: $1.2 million to $1.8 million. Coming from the estate of Edwin Wiesl Jr., a noted collector of “gold-grounds,” this altarpiece of the scholarly saint appeals to the connoisseur as well as to the gilt-obsessed.

Fede Galizia, “A Glass Compote With Peaches, Jasmine Flowers, Quinces, and a Grasshopper” (1590-1630). Estimate: $500,000 to $700,000. Notable for its shimmering fruit and life-size grasshopper, this still life comes from the Silvano Lodi collection, which is being sold over four auctions at Christie’s. Galizia was not only the foremost still-life painter in Milan at the turn of the 17th century, she is one of several female Old Masters in the sale.

Luca Carlevarijs, “A Capriccio of a Mediterranean Seaport” (c. 1705). Estimate: $3.5 million to $4.5 million. This image of a bustling port is complemented by a companion picture of a sea battle, also for sale. Carlevarijs is among the first 18th-century vedutisti, or Venetian painters of topographical views, and his work influenced Canaletto.