57

How to measure the pyramid of vision.

[figure]

As regards the point in the eye; it is made more intelligible by this: If you look into the eye of another person you will see your own image. Now imagine 2 lines starting from your ears and going to the ears of that image which you see in the other man’s eye; you will understand that these lines converge in such a way that they would meet in a point a little way beyond your own image mirrored in the eye. And if you want to measure the diminution of the pyramid in the air which occupies the space between the object seen and the eye, you must do it according to the diagram figured below. Let m n be a tower, and e f a, rod, which you must move backwards and forwards till its ends correspond with those of the tower [Footnote 9: I sua stremi .. della storre (its ends ... of the tower) this is the case at e f.]; then bring it nearer to the eye, at c d and you will see that the image of the tower seems smaller, as at r o. Then [again] bring it closer to the eye and you will see the rod project far beyond the image of the tower from a to b and from t to b, and so you will discern that, a little farther within, the lines must converge in a point.

Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.

56 * 58
I * III
Notebooks of Leonoardo da Vinci
II: Linear Perspective.
. . .
General remarks on perspective.
40,
41
The elements of perspective--Of the Point.
42,
43,
44,
45,
46
Of the line.
47,
48,
49
The nature of the outline.
50
Definition of Perspective.
51
Experimental proof of the existence of the pyramid of sight.
52,
53,
54
The relations of the distance points to the vanishing point.
55,
56
How to measure the pyramid of vision.
57
The Production of pyramid of Vision.
58,
59,
60,
61,
62,
63,
64
Proof by experiment.
65,
66
General conclusions.
67
That the contrary is impossible.
68
A parallel case.
69
The function of the eye as explained by the camera obscura.
70,
71
The practice of perspective.
72,
73
Refraction of the rays falling upon the eye.
74,
75
The inversion of the images.
76
The intersection of the rays.
77
. . .