The sitter has not been identified. He holds a palette and brushes, and is thus almost certainly a painter. This was once thought to be a self-portrait of the painter Benedetto Gennari (1633 - 1715) but there seems no reason for this attribution. It has subsequently been catalogued as Emilian School, but even this is tentative. A date of about 1650 seems likely.
The National Gallery, Trafalgar Square, London WC2N 5DN