149

Gradations of strength in the shadows.

The light which falls on a shaded body at the acutest angle receives the highest light, and the darkest portion is that which receives it at an obtuse angle and both the light and the shadow form pyramids. The angle c receives the highest grade of light because it is directly in front of the window a b and the whole horizon of the sky m x. The angle a differs but little from c because the angles which divide it are not so unequal as those below, and only that portion of the horizon is intercepted which lies between y and x. Although it gains as much on the other side its line is nevertheless not very strong because one angle is smaller than its fellow. The angles e i will have less light because they do not see much of the light m s and the light v x and their angles are very unequal. Yhe angle k and the angle f are each placed between very unequal angles and therefore have but little light, because at k it has only the light p t, and at f only t q; o g is the lowest grade of light because this part has no light at all from the sky; and thence come the lines which will reconstruct a pyramid that is the counterpart of the pyramid c; and this pyramid l is in the first grade of shadow; for this too is placed between equal angles directly opposite to each other on either side of a straight line which passes through the centre of the body and goes to the centre of the light. The several luminous images cast within the frame of the window at the points a and b make a light which surrounds the derived shadow cast by the solid body at the points 4 and 6. The shaded images increase from o g and end at 7 and 8.

[Footnote: The diagram belonging to this chapter is No. 2 on Plate III. In the original it is placed between lines 3 and 4, and in the reproduction these are shown in part. The semi circle above is marked orizonte (horizon). The number 6 at the left hand side, outside the facsimile, is in the place of a figure which has become indistinct in the original.]

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

II * IV
Notebooks of Leonoardo da Vinci
III: Six books on Light and Shade.
. . .
129
On the nature of light.
130,
131
The difference between light and lustre.
132,
133,
134,
135
The relations of luminous to illuminated bodies.
136
Experiments on the relation of light and shadow within a room.
137,
138,
139,
140
Light and shadow with regard to the position of the eye.
141,
142,
143,
144,
145
The law of the incidence of light.
146,
147
Gradations of strength in the shadows.
148,
149
light.
150,
151,
152
On the proportion of light and shade.
153,
154,
155,
156,
157
Definition of derived shadow.
158,
159
Different sorts of derived shadows.
160,
161,
162
On the relation of derived and primary shadow.
163,
164,
165
On the shape of derived shadows.
166,
167,
168,
169
. . .