You see at once that this covers a pretty wide field. But it is to be again noted that the use of chiaroscuro by the old painters meant not only the expression of the light and shade of nature, but the so arranging of the objects and the way that the light was permitted to fall on them, that certain parts of the picture became shadow, while the light was concentrated in some other part or parts. In this way the arrangement of the light and shade of a picture became a distinct element of composition, and a very important one. The quality of "light" was something to be emphasized by contrast. It is stated (whether truly or not) that the proportion of light to dark was according to a definite rule or principle with certain painters, some permitting more, and some less, space of canvas to be proportioned to light and to dark. The gradations of light and dark were studied of course; but the quantity of light spread over the canvas was calculated upon, so that the less space of light and the greater the space of dark, the more brilliant would be the main spot of light in the picture. They wrought with the quality of light and shade as an element, just as they would with the quality of line or of color, considered apart from objects or facts they might represent.
Arbitrary Lighting.—This is the arbitrary light and shade spoken of in the chapter on "Values"; and although the older painters included what we now call values in their word chiaroscuro, it is this fact of arbitrary lighting as opposed to accepting the light as it does fall, or selecting those places or times where it does naturally fall as we would like it to, that makes the difference between modern painting generally and the older method, and has made chiaroscuro as a word and as a quality of painting so much a thing of the past.
Light and Shade.—But we may use the old word with a more restricted meaning. If we use it to mean literally light and shade, the way light falls on objects and the relief due to the light side and the shadow side of them, we get a use which implies a very important and practical matter for present study.
Eggs. White against White.
Objects Visible by Light and Shadow.—If you will put a white egg on a piece of white paper, with another white paper back of it, you will see that it is only because the egg obstructs the light, the side of it towards the light preventing the light rays from touching the other side, and so casting a shadow on itself and on the paper, that the egg is visible. You will also see, if you manipulate the egg, that according as the light is concentrated or diffused, or according to the sharpness of the shadow and light, is the egg more or less distinct.
Contrast.—Apply these facts to other objects, and you will see how important the principle of contrast is to the representation of nature. Not only contrast of light and shade, but contrast of color. And you should make a study, both by setting up groups of objects in different lights, and by studying effects of lights wherever you are, of the possibilities and combinations of light and shadow.
Constant Observation.—The painter is constantly studying with his eyes. It is not necessary always to have the brush in your hand in order to be always studying. Keep your brain active in making observations and considering the relations in nature around you. The amount of material you can store up in this way is immense, to say nothing of the training it gives you in the use of your eyes, and in the practice of selection of motives for work. Schemes of color or composition are not usually deliberately invented within the painter's brain. They are in most cases the result of some suggestion from a chance effect noticed and remembered or jotted down, and afterwards worked out. Nature is the great suggester. It is the artist's business to catch the suggestion and make it his own. For nature seldom works out her own suggestions. The effect as nature gives it is either not complete, or is so evanescent as to be uncopyable. But the habit of constant receptivity on the part of the artist makes nature an infinite mine of possibilities to him.