Painting's Principles: Plane Surface, Shadow, Perspective
A geometric proof of images on opposing plane surfaces, the shadow principle, and the three parts of perspective.
Continuing the first part of the Treatise on Painting, this leaf states that painting extends no further than the surface by which a visible body is feigned. A chapter titled 'Principle of the science of painting' proves, with a small diagram, that a flat surface r s casts its whole image into an opposing flat surface o q, being wholly present at angles o, q and p. Further chapters name the second principle of painting as the shadow of the body, and declare the science of painting the mother of perspective, dividing perspective into three parts: outlines, the diminution of colors, and the loss of union of bodies at distance. The running header reads 'PRIMA' with the folio number at upper right.
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A plane surface casts its whole image on the opposing surface
Let r s be the first flat surface and o q the second, set facing it. The surface r s is wholly present in o q, and wholly in o, in q and in p, because r s is the base of the angle o and of the angle p, and so of infinite angles made in o q.
The second principle of painting is shadow
The second principle of painting is the shadow of the body that painting feigns. Its principles will be given, and with them one proceeds to 'sculpt' the aforesaid surface.
The science of painting is the mother of perspective
Painting extends to all the colors of surfaces and the figures of bodies clothed by them, with the due degrees of diminution according to distance. This science is the mother of perspective, which divides into three parts: the outlines of bodies, the diminution of colors at various distances, and the loss of their union.