Giorgione and Titian or Cariani ?
This drama reminds me of a long forgotton TV show, What's my Line? Whatever, Tyler Green has a nice series of posts on Modern Art Notes about the latest round in the attribution of this painting. Personally I think the attribution to Cariani is wrong, but what do I know? I'm no expert on the period. To satisfy my curiosity I ran it through the gridmaker.
Giorgione and Titian
Portrait of a Venetian Gentleman, c. 1510
oil on canvas
Overall: 76.2 x 63.5 cm (30 x 25 in.)
National Gallery of Art, Washington, DC
The yellow divisions are the Golden Ratio's of the height and width (.382 and .618). The reddish lines are 1/4 and 1/2 divisions and the 1/2 diagonals. The green and cyan are 1/3, 1/6, 1/9 divisions and the 1/3 diagonals. The National Gallery link has photographs and more information