147.
OF PAINTING.
That part of a body which receives the luminous rays at equal angles will be in a higher light than any other part of it.
And the part which the luminous rays strike between less equal angles will be less strongly illuminated.
SECOND BOOK ON LIGHT AND SHADE.
Gradations of strength in the shadows (148. 149).
148.
THAT PORTION OF A BODY IN LIGHT AND SHADE WILL BE LEAST LUMINOUS WHICH IS SEEN UNDER THE LEAST AMOUNT OF LIGHT.
That part of the object which is marked m is in the highest light because it faces the window a d by the line a f; n is in the second grade because the light b d strikes it by the line b e; o is in the third grade, as the light falls on it from c d by the line c h; p is the lowest light but one as c d falls on it by the line d v; q is the deepest shadow for no light falls on it from any part of the window.
In proportion as c d goes into a d so will n r s be darker than m, and all the rest is space without shadow.