Page:Popular Science Monthly Volume 47.djvu/480

466 imperfect focusing. To understand this, let us for a second time observe the artist before his easel. If he is painting a bunch of flowers, with a white rose near the center, and if he wishes this rose to stand out in strong relief, he focuses his eyes naturally and normally upon it, and reproduces on the canvas the same clearly denned, well-focused flower which he sees. To the other flowers of the cluster he does not care to give the same prominence, and sketches them with less distinctness, or else focuses his eyes purposely for a point in front of the bouquet or behind it, thus blurring the colored flowers and purposely transferring to the canvas an ill-defined image of them. For example, teachers often find fault with their pupils, saying, "The trouble is, you see too much; you should not paint so exactly." An artist, holding an important public position as a teacher of painting in Boston, recently showed me lenses which were.used by the students when learning thus to focus the objects imperfectly. Given, then, this fact of imperfect vision on the part of the artist, either in the form of astigmatism or in the form of undue contraction of the focusing muscle, let us consider its effect in relation to three factors—namely, drawing, values, and color.

As to the first, imperfect vision is unquestionably a disadvantage, as we have seen. The draughtsman owes his power to two things—accuracy of eye, which enables him clearly to perceive forms; and dexterity of hand, which enables him to reproduce them. Truth in one is as indispensable as in the other.

Next, as to the question of values. This term, as we know, is used in a certain sense to express perspective, or, more exactly, the relative distance of an object in the foreground as compared with another more or less in the background. In the case of the bouquet, just cited, the white flower in the center, having the highest relative value, is painted exactly in focus. A certain amount of artificial adjustment of focus by the artist is an undoubted advantage for the rest of the bouquet, however, and the habit of focusing the eye for some point in front of the picture or beyond it is, therefore, practically universal among artists, though in most instances they are not conscious of the act. In a similar way the effects called technically "distance" and "atmosphere" are also best secured in this way. The two factors thus far considered relate to representations in black and white as well as to those in color.

We come now to consider the third factor, that of the mixing of colors. We shall find that this involves the blurring or overlapping of images on the retina, which can be caused by astigmatism, if it exists in sufficient degree, or by improper focusing. It is usually produced by both of these together and by another function dependent on the combination and