Molanus argues that artists should follow the pictorial tradition set by other artists or study the written sources regarding the subject.
“It is, therefore, a source of joy to see the features and lines of the portrait respected in the paintings of Christ, the Mother of God and the princes of the Apostles, as they were fifteen hundred years ago, the painters have followed in this matter the tradition of our ancestors which they learned from the paintings. And if from the paintings, they do not have the possibility of apprehending it easily enough, they will be able to grasp it in a slightly more satisfactory way thanks to the writings of certain people who refer to it.”
“Itaque iucundum est videre quod in pictura Christi, Deiparae et Principum Apostolorum, ea forma et effigiatio observetur, quae observata fuit annis mille quingentis, sequentibus hac in re pictoribus maiorum quam ex picturis didicerunt traditionem. Quod si quae ex picturis non satis comode percipi possint, poterunt eadem paulo plenisu comprehendi adhibitis quorundam scriptis.”
Lentulus Nicephorus Callistus
Molanus 1996, 286.