If any projection occurs on a plain on which a shadow is thrown, the shadow takes the form of the projection, as it passes it; but, if it ends upon it, the shadow will be shaped by the object that flung it, still qualified by the section of the projection. The rough surfaces of many things would describe the same in a lesser degree.
Light objects, as they retire, become darker; and dark ones, lighter; but light ones are seen at a greater distance than dark.
The darkest opposing object brought up against the most retiring, should not extend itself to the edges of the picture, but let the half tints creep in, to bring the light down with more effect—diffusing it more extensively.
The shadow on the ground on which it is thrown, should be darker than the object projecting it; and, if the object be round, a reflected light will be found on the edge where it joins the shadow, as in a column.
I placed a chair in the shade, and the sun's reflection threw a shadow from it!
The light of every body is qualified by the ground that surrounds it.
Breadth is acquired by blending the light parts of the figures with the light of the ground; and the same rule will apply to the shadows.
When the ground of the picture is mostly dark, the lights, in my opinion, should take some one or other good decided form in composition, in their developement, as their meaning is only to be explained by themselves. ([Plate 4.])
If a single light or luminous mass be surrounded on all sides by a dark ground, one or more of its edges should be strong and cutting; and if a dark centre be placed on a light ground, if the same management be not observed, it will look like a hole.
Leonardo says 'The ground which surrounds the figures in any painting, ought to be darker than the light part of those figures, and lighter than the shadowed part.'