This is a few years late, but may help the next reader. . . In the book, "Adventures with Pinhole and homemade cameras," they have the very image of Justin's you posted and they give the specifications as: Exposure in ambient room lighting was 15 minutes at f/186 on 4 x 5in iso 100 black and white film. He filled the beer can with water so it sank to the bottom of his bathtub (and filled the duck with sand). hope this helps!