Light, shadow and the visual pyramids of a sphere
How the size of a ball's shadow on a wall varies with the size and distance of the light
On a grey prepared sheet Leonardo works through how a spherical body casts shadow onto a facing wall, drawing several small figures of a ball between a light source and a screen. He argues that the larger and more distant the light, the more of the ball it illuminates and the smaller the shadow it throws on the wall (walls lettered p q, m o, b c). A further diagram sets a ball within paired visual pyramids drawn from an eye and reasons that from a single point no more than half a sphere can ever be seen, the pyramidal lines finding their bases at a b and d e. A schematic head laid out with construction lines appears at the foot of the sheet.
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Size of shadow governed by size and distance of the light
In a series of small figures a ball stands between a light and a wall. Leonardo states that the greater the light is compared with the object, the more of the object it reaches and the smaller the shadow on wall p q; likewise the more distant the light, the more of the ball is lit and the smaller the shadow on wall m o. Conversely, the less a luminous point sees of a spherical body, the larger the shadow it casts on wall b c.
A ball within two visual pyramids: only half can be seen
A ball is set within two visual pyramids drawn from an eye, lettered c a d e b f. Leonardo argues that a sphere can never be seen from a single point except by half or less, and by less the nearer one stands. As much of the mirror as point c sees, that much of the mirror sees it, the pyramidal lines from c ending at bases a b and those from f at bases d e, each pyramid centred on the centre of the mirror.
Schematic head laid out with construction lines
At the bottom centre of the sheet a frontal human head is sketched within a framework of construction lines. It is drawn separately from the optical diagrams and is not covered by the transcribed notes. It reads as a proportional or perspectival study of the face.