When the artist leaves the study of line and seeks to combine light and shadow, Construction and contour, ho steps into :i new world. IT is drawings begin to take on a quality of existence, for through light and shadow we delineate form, and all the visible world is only light on form.
lkit nature, until her ways and laws arc understood, can seem so complex as to be almost overpowering. Usually her forms arc surfaced with endless variations of texture, and the relationship of her forms, as well as of man-made forms, to basic form is not always evident So some simple plan must be devised to help us understand the complexities before us.
As an approach, we must simplify both light and form. The basic forms start us on the way, since they do not have confusing surface irregu-larties or changes of color or texture. They are a simple white, with a smooth surface, thus allowing us to look at the effect of light uninfluenced by other factor's.
There is no better place to start than with the sphere, which seems to be the basic form of the universe* With the sun lighting our universe, the spheres of all the planets are always half in light and half in shadow, but because the planets are rotating on their ases, any single spot on these spheres moves from light, into shadow, and back into the light Jn the course of a single ievolution. Since the light on a sphere merges into the shadow through gradually darkening halftone, the rotation of the sphere of Otir earth produces the gradual darkening of the daylight which we know as twilight and evening. At night we have reached the shadow side where the parallel rays of the sun can no longer reach us. At noon we are in the middle of the lighted area, and at midnight wc arc in the middle of the shadow area.
These facts arc the basis of all the light and shadow that We shall ever draw, On a lighted sphere there is a highest point of light, where the surface is nearly flat or at right angles to the source of light. That part collects more light rays than any other. This we call the highlight. It is always at the shortest distance from the surface of tile form to the light source. As the surface luriis a way from the source, it collects fewer rays and lilis causes halftone. The edge of the shadow then begins where the light rays are at a tangent to the surface of the sphere. Therefore, if wc have an established direction of the source of light, we can approximate where the shadow begins on any rounded or spherical for ml It is always at the halfway mark around the form.
The first basic law of light thou is: The light from tfrtj/ Ungle source must. Irütel in a straight fine. íi tul therefore cannot reach more than half-tcdij around arty routul form.
The next law follows from the first: Any sw-face is lighted according to the angle of its surface ú¡ relation to the direction of the light source. The brightest planes then are either flat or at right angles to the light. With every increase iii the curve away from the perpendicular to the light source, the value of the plane darkens until it leaches the maximum darkness, which is at and just beyond the edge of the shadow.
The next law follows in orderly sequence: Only a fait plane can b& evenly lighted in the same talttc. .since curving and rounded planes always produce the effect of graduated tones of halftone. Here then lies the seeict of rendering light on form. The flat areas are flat in tone or value, The rounded areas ate modeled in graduated tones. The way wc treat the area shows the observer roundness or flatness, and thus establishes the identity of the form,
The sphere or egg is the only form without flatness. The cuhc or block is without roundness. Therefore the sphere or like forms can be rendered only in graduated tones, and the cube or block only in flat tones. All forms are composed either of fat planes or rounded surfaces, or a combination of the two.
Now let us think of shadow. When a surface dips so that a ruler laid on the plane cannot point at the light source, that area must bo indicated as in shadow. That ls why there can be shadows between lighted areas, as in the folds of drapery. In fact, any depression or indentation identifies itself with halftone or shadow. Any protuberance on the surface has lighter value on the sides facing the light and halftone on the other sides, and, if it is high enough, casts a shadow on the surface.
Getting back to the sphere, let us look carefully at the shadow side. We find that the darkest part of the shadow occurs near the edge of the light. The shadow can be a flat tone only if there is no reflected Hght, This is the way we see the half-moon. There is nothing to light up the shadow. However, since everything in the light also reflects it, the shadows we see have usually taken on some of tlio reflected light of lighted planes nearby, and therefore the tones within the shallow are somewhat lighter than its edges. This darker edge of a shadow on a rounded form is what illustrators call "the hump." Being darker, it tends to accentuate the brilliancy of the lighted areas next to it, and also to give airiness and luminosity to the shadow areas. This "hump1 occurs only when the initial light has been rcflectcd back on the objcct. Unless the reflected fight is thrown directly back at the light sourcc, this darker edge disappears, since it is caused by the fact that neither the light nor the reflected light can fall on the angle of the plane or surface at that point. To get this beautiful effect photographically, the fill-in light should be pointed directly at the main light sourcc, and be of not more than half its intensity. This is the sccrct of preparing good photographic copy from which to draw.
Since any object may be moved about in relation to the light source, and we may look at the object from any viewpoint, we can see light and shadow in any proportion on the object. If we arc looking at the light sourcc, we see any objcct between us and the source in full shadow, for we are on the shadow side. If the light source is directly behind us or between us and the object, we see the objcct in full light without shadow. This is the effect we get in photographs with a fla?;h bulb at the camera, A drawing under those conditions would Ixn composed only of light and halftone, with the darkest darks at the edges or contours. If the object is placed at right angles to our position and to the light sourcc, it is seen as h;dl- in light and half in shadow. If placed in one of the quarter positions it is either three-quarters in light and one-quarter in shadow, or the reverse.
Understanding these facts, we can draw a sphere as if it were lighted from any direction we choose. By turning the drawing on end we can get the effect of the light source being above or below the spheres. Incidentally, the quarter lightings are usually more satisfactory pictorial ly than half light and half shadow. Having either light or shadow dominate is more effective than an equal division between them. The full-front lighting is very good for simple or postery effects. It is used a great deal by Norman Rockwell, among others.
The use of two light sources tends to break down the solidity of the form. Crisscross light-ing— light sources at both the right and the left of the artist — is especially bad because it breaks up everything into small lights and shadows. Outdoor sunlight or daylight is the perfect light for drawing or painting.
The sphere iu light and its cast shadow on the ground plane arc shown on page Si. The central rav of light is a line passing through the ccntcr of the sphere from the light source. The point at which this line hits the ground plane is the center of the cast shadow, which is always seen as an ellipse.
Spheres A and B on page 82 show the very important difference between the effects of direct light with its cast shadow and of diffused light with its diffused shadow. In sphere A, the
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SHADOW FROM A SPHERE IN PERSPECTIVE
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