Before the advent of cameras, movies, magazines and modern painting techniques the only way people could see pictures of things, especially in color were by viewing oil paintings. From the renaissance on large studios were established throughout Europe where artists, often under the direction of a master turned out innumerable paintings.

In the capitals of Europe art studios were legitimate businesses and thrived on commissions from the church, state and wealthy patrons Many paintings of rigorous and allegorical subjects were designed and executed by great masters like Titian or Rubans. The originals were displayed with the hope of garnering commissions for copies. For instance Titiau who worked in the 16 century Venice had a very active workshop and made many copies of his originals. These copies, some executed by Titian himself, others by painters in his employ were sold to cardinals, aristocrats and nobles.

Ruains did the same as did many others. Even individual artists who never established a working studio like Cauuavaggio made many copies of their originals. Today we call those copies "contemporaneous copies" meaning they were executed at the time the original was made. It is up to today's present experts to determine weather a contemporauious copy was executed by the hand of the master, by the master and a student or by a student only.

My criteria for making a copy is that the original was in fact copied in the period by the master or his workshop. The other criteria being that if copies of a specific period painting are not known to exist, then the painting must be of a type one could reasonably expect to have been copied in the period.