How the species of things fill every point of the air
Visual pyramids on a single base, and the whole object seen from any point of the circle
A large fan of finely ruled rays sweeps out a half-circle converging on a single point, illustrating Leonardo's claim that the 'species' of visible things are present at every point of the air without any interval, so the eye sees the whole object from wherever it stands within the circle. The text argues that among pyramids of rays drawn from one base, the one with more unequal angles is thinner and a more deceptive indicator of the base's true width, while the widest angle derives from the least foreshortened viewpoint. A smaller lower diagram compares four pyramids on one base, the most powerful being the thickest, whose base-angles are most alike. A brief opening note observes that a reflection is most evident where it ends against greater darkness.
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The species of things fill every point of the air
All the points forming the tips of the pyramidal species of things are joined throughout the whole air without interval. Nature has ordained that in every point of the air the species of all facing objects concur by a pyramidal meeting of rays; otherwise the eye could not, from any point between itself and the object, see the object's form and quality.
The whole object seen from any point of the circle
Let a c be the thing seen and the eye its beholder. Wherever the eye moves within the circle a d e f c, it always finds itself at an intersection from which the whole thing a c can be seen. The great fan of rays converging at d demonstrates this concourse.
Which pyramid lies about the width of its base
A pyramid that departs from its base with more unequal angles is thinner and a more deceptive indicator of the base's true breadth. A thinner pyramid must derive from a more foreshortened place, a wider one from a less foreshortened place. Point m marks the most foreshortened part of base b c, n the least, where the angle appears wider.
The strongest of many pyramids on one base
Among the many pyramids raised upon a single base, the most powerful is the thickest, and the thickest is the one whose base-angles are most alike to one another.
A reflection is clearest against greater darkness
That part of the reflection is the more evident which ends in a place of greater darkness.