The Eye, Shadow Proportions, and a Man Moving Weights
A marginal eye diagram (d, n, a, b, c) on distinct edges, plus notes on shadow and the mechanics of lifting a load
The page gathers three of Leonardo's late themes under separate headings. Under 'Of the eye' he argues, with a small marginal diagram lettered d, n, a, b, c, that the edges of a body are least distinct when nearest the pupil, because images from the space beyond the edge mingle with those of the edge itself. A 'Painting' note states that the shadows of bodies keep the same proportion as their natural darknesses, and a 'Of human motion' note treats a man as the mover of a weight, tracing the different lines of motion and the role of the centre of gravity outside the base of support.
On this page
Why an edge is least distinct when nearest the pupil
The edges of a body set opposite the pupil grow less distinct the closer they lie to it. Testing edge n against pupil d, the pupil also takes in the whole space a c lying beyond that edge, and the images from that space blend with those of the edge, so one image confounds the other and robs the pupil of clear knowledge of the edge.
Shadows in proportion to a body's natural darkness
Among bodies of different darkness that share one and the same light, the proportion between their shadows equals the proportion between their natural darknesses. The same reasoning is to be understood of their lights.
A man as the mover of a weight
When a man is to move a weight, the motion follows different lines: lifting from low to high by stooping and straightening, dragging behind, pushing forward, or hauling down through a pulley. The man's weight pulls in proportion as his centre of gravity falls outside the centre of his support, aided by the force of the legs and the bent back straightening.