For under the freest painting, if it be good, there will be found a bed-rock structure of well-constructed masses and lines. They may never be insisted on, but their steadying influence will always be felt. So err in your student work on the side of hardness rather than looseness, if you would discipline yourself to design your work well. Occasionally only let yourself go at a looser handling.
Variety of Gradiation.
Variety of gradation will naturally be governed largely by the form and light and shade of the objects in your composition. But while studying the gradations of tone that express form and give the modelling, you should never neglect to keep the mind fixed upon the relation the part you are painting bears to the whole picture. And nothing should be done that is out of harmony with this large conception. It is one of the most difficult things to decide the amount of variety and emphasis allowable for the smaller parts of a picture, so as to bring all in harmony with that oneness of impression that should dominate the whole; how much of your scale of values it is permissible to use for the modelling of each individual part. In the best work the greatest economy is exercised in this respect, so that as much power may be kept in reserve as possible. You have only the one scale from black to white to work with, only one octave within the limits of which to compose your tone symphonies. There are no higher and lower octaves as in music to extend your effect. So be very sparing with your tone values when modelling the different parts.
XIV
UNITY OF MASS
What has been said about unity of line applies obviously to the outlines bounding the masses, so that we need not say anything further on that subject. The particular quality of which something should be said, is the unity that is given to a picture by means of a well-arranged and rhythmically considered scheme of tone values.
The modifications in the relative tone values of objects seen under different aspects of light and atmosphere are infinite and ever varying; and this is quite a special study in itself. Nature is the great teacher here, her tone arrangements always possessing unity. How kind to the eye is her attempt to cover the ugliness of our great towns in an envelope of atmosphere, giving the most wonderful tone symphonies; thus using man's desecration of her air by smoke to cover up his other desecration of her country-side, a manufacturing town. This study of values is a distinguishing feature of modern art.
But schemes taken from nature are not the only harmonious ones. The older masters were content with one or two well-tried arrangements of tone in their pictures, which were often not at all true to natural appearances but nevertheless harmonious. The chief instance of this is the low-toned sky. The painting of flesh higher in tone than the sky was almost universal at many periods of art, and in portraits is still often seen. Yet it is only in strong sunlight that this is ever so in nature, as you can easily see by holding your hand up against a sky background. The possible exception to this rule is a dark storm-cloud, in which case your hand would have to be strongly lit by some bright light in another part of the sky to appear light against it.