There are various ways of obtaining contrasts and two of the most common are illustrated by Figure 19. A white spot against a black background always shows so plainly that the eye goes to it very quickly. Likewise a black spot against white attracts immediate attention. Now, many objects in nature are similar to these spots. For instance, a white house in strong sunlight against a background of dark trees is similar to the white spot mentioned above and the eye sees it quickly because of the contrast. A dark building silhouetted against the sky illustrates the idea of the dark spot against the light background. Now, a white spot against a dark tone appears even whiter if the dark tone grades gradually to white so as to have no sharp edges to lead the eye from the spot itself, and in the same way a dark spot against a white background will appear even blacker if the white background grades out gradually to gray or black, for this will cause the white background to appear even whiter by contrast. The spots "A" and "B" at the top of Figure 19 illustrate this point as do also the small sketches of houses "C" and "D."
Figure 18. The Same Subject Drawn with BroadLines and with Fine Lines. A Type of Sketch to he Submitted by the Architect to His Client to Show Proposed Alterations.
Figure 19. Illustrating Method of Focusing Attention by Means of Strong Contrasts of Light and Dark.
Figure 20. Illustrating the Focusing of Attention at the Center of Interest by Means of Strong Contrasts of Light and Dark.
It must be remembered, too, that the light conditions in nature vary constantly, so it is possible for an object to appear light against dark during certain times of the day and dark against light at others. For example an office building in bright sunlight might appear light against a deep blue sky until evening when it might change to a dark silhouette against a brilliant sunset sky. The drawings of the lighthouse, "E" and "F" at the bottom of Figure 19 still further illustrate this point. This example is rather extreme but serves to make clear that two sketches of a building made at different hours might vary greatly from each other. Therefore, when working from nature it is necessary to draw very quickly as the light is constantly changing.
In order to prevent a sketch being broken up into too many equal areas of light and shade, thus causing confusion, it is often well to look for some one leading light area and some one leading dark area in the objects to be drawn. If a sketch is to be made of a dark stone building, that perhaps becomes the leading dark area and the light area may be found in the foreground or sky or both. On the other hand, if a building is light in tone it becomes in itself the leading light area and the background of trees or sky or the foreground masses become the dark area. Having decided on these leading light and dark areas, look for subordinate areas, such as doors, roofs or similar details and give each just its proper amount of accent to make a satisfactory composition of the whole. It is usually true that we find in the same subject many contrasts of light against dark and dark against light, but in making a sketch remember that the eye would see the strongest contrasts near the fecal point, or center of interest. Look for the sharpest accents here and in the drawing subordinate all others, for unless this is done the eye will jump from one point to another, which will cause the picture to lack unity and repose. It is easy to hold the eye at the center of interest as has been shown above if strong contrasts of light against dark or dark against light are shown there. The two sketches on Figure 20 still further illustrate this principle of contrast. The center of interest in the first is around the arched entrance and here the contrasts have been kept sharp and strong. First there is the light spot of the opening to the street. Then in sharp contrast to this is the dark tone of the archway itself. This in turn is strong in its contrast with the lighter tones of adjacent walls, and these light tones on walls and street are emphasized further by the fact that they are graded to dark at the edges of the sketch. In the second sketch, showing one of the earliest forms of timber construction, there are similar contrasts to hold the eye to the center of interest. First the dark doorway becomes the focal point. This is strong in its contrast with the surrounding light walls of the building and with the street, while these light tones are in turn surrounded by the large dark area of roof tones, verge board shadows and the like, which are graded outward to the edges of the sketch.
In starting a pencil drawing the student is urged to make a preliminary study of the values of light and dark as soon as the outline has been completed. This study can be made to good advantage on tracing paper directly over the outline drawing, and when completed will serve as a guide for the actual rendering. Once the values have been determined in this way, the student is free to give his attention to the technique. At this point it might be well to offer a few suggestions. First of all we must work for variety of line, for it is impossible to express all materials, and surfaces with one type of line. Smooth, straight strokes suggest smooth surfaces, while irregular strokes are best for representing rough, uneven surfaces. As a rule it is well for the strokes to follow the structural lines of the objects to be represented. This means that the strokes used on vertical walls will usually be vertical or perspectively horizontal. The roof lines will follow the slope of the roof or vanish towards a point with the other parallel lines. Curved surfaces can as a rule be best represented by the use of curved lines.
It is suggested that the student try a few practice sketches to further fix in his mind some of the ideas suggested in this text. Do not be discouraged if the first results are not entirely satisfactory; it is only by making mistakes and profiting by them that one can learn to draw.