LONDON (REUTERS).- A major exhibition in London brings together works by Italian painter Giovanni Antonio Canal, best known as Canaletto, and some of his biggest rivals who fought for artistic and commercial supremacy.

Painting Venetian views was big business in the 18th century, as wealthy English aristocrats on their Grand Tour sought to take back with them a memento of the canal city.

Canaletto adopted a more commercial approach to his art in the 1730s, largely thanks to his association with British patron and agent Joseph Smith who would promote the painter to patrons coming from abroad.

One way the artist sought to earn more money was to paint smaller pictures which were more easily transported home.

It was also in the 1730s that a significant rival to Canaletto emerged. Michele Marieschi focused on painting quickly and often brought in other artists to paint human elements of grand Venetian landscapes which he was less comfortable with.

"Marieschi could work very quickly and thereby undercut Canaletto's prices," said Dawson Carr, curator at the National Gallery where "Venice: Canaletto and His Rivals" runs from October 13 to January 16, 2011, before moving to the National Gallery of Art, Washington.

"Therefore more tourists came to Marieschi because they could get the paintings more quickly."

ACCURACY SACRIFICED
The show, sponsored by Credit Suisse and uniting some 50 loans from collections around the world, opens with a work by the founding father of Italian view painting, Gaspare Vanvitelli dated 1697, the year of Canaletto's birth.

By the 1720s, Canaletto was already beginning to eclipse another of his forerunners, Luca Carlevarijs, and his detailed, animated works which capture the effects of sunlight soon made Canaletto Venice's go-to scene painter.

The fact that most pictures in the genre were destined for the export market gave artists license to distort the truth, meaning perspectives were changed and buildings both shortened and rotated to show off their most impressive aspect.

"By and large Venetians didn't buy this sort of thing -- they could walk out of their doors and see it," Carr said. "Back in England, probably no one would notice such details."

Included in the exhibition is one Canaletto which was lucky to survive.

"The Bacino di San Marco", dated 1738-39, originally went to Castle Howard in England, but was sold on in 1939, a year before a fire swept through the country house and destroyed many works by the same artist.

The final two rooms of the show focus on the rise of Francesco Guardi, who ensured what the gallery called a "glorious final chapter in the history of Venetian view painting."

His brushwork was more sketchy than Canaletto's and sometimes buildings were rendered in semi-abstract form.

But he also stressed the natural over man-made, meaning his paintings looked forward to trends in painting in the 19th century.

(Editing by Steve Addison)