Kepler, Galileo and Guidobaldo were the leading optical theorists of their generation. Galileo studied with Guidobaldo while he was composing this treatise. Galileo’s mastery of perspective was acknowledged by his student, Vincenzo Viviani, who wrote: “The famous Cigoli, regarded by Galileo as the foremost painter of his time... particularly prided himself on being able to say that in perspective Galileo alone had been his master.”