Shadows are of utmost importance from many standpoints. The cast shadow is the shadow of an object upon another surface and the shadow is that on the object itself. Al though these two classes of shadows are sub ject to different minor influences thcv are in general subject to the same major influences. In this brief discussion they will be considered together. There are three dominant factors which influence the appearance of shadows: (1) The position of the dominant light-source de termines their general direction; (2) the solid angle subtended by the light-source determines the character of the shadow-edges; (3) the amount of light scattered or diffused by the surroundings determine the brightnesses of the shadows. By controlling these three factors the sculptor, the photographer, the lighting specialist, the architect, the museum director and others are able to produce the desired modelling of the subject.
The sculptor does not actually strive to re produce an object in true relative dimensions. He paints in light and shade with his chisel by leading lines and areas of light and shade in order to fix an expression of light. The appearance of a model depends upon the light ing and in a similar manner the final product should receive a proper lighting resulting from thoughtful consideration of these factors. But these factors appear not to be considered in many museums because we often find sculpture displayed collectively in large rooms in which these factors differ widely. A large skylight flattens the objects especially if the surround ing walls and floors are highly reflecting. In general, sculpture should be exhibited amid brighter surroundings than paintings because the shadows should not be too dark. Dark, sharp shadows produce a harshness and severity appropriate to a relatively few subjects but in. general the.light-source should be extended to a moderate solid-angle and the shadows should receive an appreciable amount of light from the surroundings.
The effects are usually more satisfactory if the object is so placed with respect to the dominant light-source that the shadows fall aslant. In large rooms sculptured objects are usually displayed to the best advantage when near the walls and properly oriented. Such rooms when illuminated by windows are usu ally less satisfactory owing to the multiple shadows due to two or more light-sources (windows) and to the nearly horizontal direc tion of the dominant light. The effects of the position of a small light-source are shown in the upper four illustrations in Fig. 3. The lower four illustrations show various lighting effects as noted in each case. The head is a plaster cast of the head of Laocoem and it is evident that some of the lights fail to suggest the tragic expression of this wonderfully ex pressive antique sculpture. In the lightings
shown in Fig. 3 an attempt has been made to illustrate the influence of the three factors already noted so that they do not represent com plete lightings which would ordinarily be en countered. However in Fig. 4 are shown three lightings which were just as found in practice. The head wasplaced on the wall at a height of five or six feet in a room having windows on two sides and equipped with direct and in direct lighting fixtures hung from the centre of the ceiling. The harsh effect of the direct light ing is evident. This is due to the small solid angular extent of the light-source measured at the object and to the relatively less light which falls upon the shadows. The indirect lighting, in which the ceiling is the dominant source of light, produces softer shadows, because their edges are less defined and brighter. The un satisfactory direction of daylight and the effect of multiple shadows from the three windows— two on one side and one on an adjacent side — is evident in the third illustration in Fig. 4. The best lighting of this subject as is usually the case is from a source at an angle between the horizontal and the vertical. The ideal method of exhibiting three-dimensional objects is to provide an environment and lighting suit able to the object. This ideal is seldom pos sible of attainment in practice but it may be approached in various ways. Objects may be placed. near the walls and properly oriented if the light-source is a ceiling skylight, an in directly lighted ceiling or a central fixture. They may be placed in alcoves and thus obtain an approximation to an individual environment or they may be grouped in small rooms which are properly lighted. If windows are used should be located high as a general rule. It is interesting in this connection to study various museums for there are many unsatisfactory con ditions to be found and some which indicate distinct steps toward the ideal in respect to lighting and other environments.
Low relief is not so susceptible to careless lighting although highly diffused light or such a condition as approximately equal intensities of light from several directions has a greater tendency to flatten it and it should be lighted in general with more directed light than sculpture of true dimensions. Incidentally it is of inter est in this connection to note that low relief approaches the principles of drawing usually more closely than the principles of sculpture in true dimensions.