The Italian painter Francesco Guardi (1712-1793) is famed for his oil sketches of Venice and its lagoons, loosely painted with open, clearly visible brushstrokes and a sense of the sparkle of light.

The records of his parish in Venice show that Francesco Guardi was baptized on Oct. 5, 1712. His father, Domenico, who died when Francesco was 4, had a workshop. Francesco and his elder brother, Gian Antonio, worked in a small studio, carrying out such orders as they could get for almost anything the client wanted: mythological pictures, genre, flower pieces, battle scenes, altarpieces, and even, on rare occasions, frescoes. They did not hesitate to copy compositions by other artists, but what they borrowed they always transformed into something more capricious, less stable, more fragmentary in the refraction of light.

Francesco did not emerge as an independent personality until 1760, when his brother died. Then, 48 years old, he married, established his...