On perspective: apparent size and the proportion of light and shade
Equal things equally distant appear equal; light and shade keep their objects' proportion
Pen notes gathered under the heading 'On perspective.' Leonardo states that things of equal size, equally distant from the eye, are judged of equal size by that eye, and that the shaded and lighted parts of opaque bodies keep the same proportion of brightness and darkness as their objects. Geometric figures — a square with crossed, extended diagonals and a square inscribed in a circle — accompany the text.
On this page
Equal things equally distant appear equal
Things of equal size, standing equally far from the eye, are judged by that eye to be of equal size. This is the perspective principle governing how measured distance and apparent magnitude relate.
On perspective (diagram of crossed diagonals)
The proposition sits under the rubric 'On perspective,' accompanied by a square whose two diagonals are drawn crossing and then prolonged beyond it — a construction for how converging lines carry apparent size.
Light and shade keep the proportion of their objects
The shaded and lighted parts of opaque bodies stand in the same proportion of brightness and darkness as the corresponding parts of their objects. Tone is thus transferred proportionally from object to depicted body.