Zaccolini's treatise has four parts that discuss different theories of painting. The treatise is most noted for Zaccolini's theories on optics and vision and there how they relate to painting.
Raphael uses color, light and shadow in a way that shows he had a clear understanding of optical theories. The fresco shows a shift toward naturalism within art as more artists were beginning to understand optics and the role they play within art.
Leonardo da Vinci had many notes on painting which were turned into a treatise after he passed away. The treatise discusses da Vinci's theories relating to optics, color, perspective and other elements of painting.