Why Painting Cannot Match the Relief of Nature
Treatise on Painting: the two eyes see behind an object, with a diagram of binocular vision
A text page headed 'PARTE' carrying a geometric diagram of two eyes viewing an object. The text concludes that undiminished particles at equal distance do not shrink the object, so painting does not diminish as sculpture does, then argues that no painting, however perfect in outline, shade, light and colour, can show the same relief as nature unless nature is viewed at a distance with a single eye. A ray diagram labels the two eyes a and b, the object c, and the space e-d-g-f seen behind it.
On this page
Painting does not diminish like sculpture
The passage closes the earlier demonstration: lines terminating at one same distance are without diminution, so the undiminished particles do not reduce the sum of the object, and therefore painting does not diminish as sculpture does. This is Leonardo's resolution of why the flat painted image reads larger than a carved relief.
Two eyes see behind an object; the single eye and relief
It is declared impossible for painting, however perfectly imitated, to show the same relief as the natural object, unless that object is seen from far off with a single eye. The proof takes eyes a and b whose central lines meet at object c, while the lateral lines let eye a see the space f-d and eye b the space g-e, so both together see the ground behind c.
Diagram of binocular vision
A pen diagram in the lower half of the page shows two eyes at the top joined by lines converging on a small circle (the object) and spreading to a horizontal base line marked with letters. A second grouping of upright forms appears to its right. The drawing illustrates the geometry of the surrounding text.