The portrait photographer and also the por trait painter deal with the same modelling characteristics of light and shade. Large sky lights, especially on dark days, cannot be sufficiently reduced in area to render satis factory modelling in most cases without re ducing the intensity of illumination to a low value which is often unsatisfactory. Artificial light-sources are much more adaptable to the needs of both the photographer and the portrait painter because they are more readily con trolled as to solid-angular extent, position and general distribution of light. Such units are available and are being adopted for this work. One of the chief principles of obtaining light and shade effects in the studio is shown in Fig. 5. If ab represents a vertical skylight the same light and shade effects will be obtained at o by a light-source of the size of cd or cf if the other dimension is reduced a corresponding amount in each case. Thus the same effect may be obtained with a smaller source placed closer to the subject and it is evident that a smaller room may be used.
The architect depends finally upon light, shade and color to realize his desired effect. By means of modelled ornament, pigments, lighting effects and relative brightnesses of the various important areas, the architectural pic ture is completed. Numberless architectural in teriors testify to the lack of a common goal for all those who contribute toward the light and shade effects. The distribution of light and shade largely influences the mood or spirit of the interior and the simple laws which govern light and shade effects should be applied with the final aim definitely in mind. The im portance of lighting in architecture may be seen in any interior and it may be illustrated by photographing an interior under different lightings or by means of a detail. In Fig. 6 are shown the various expressions of the same molding under five different lightings. Lighting is often responsible for certain illu sions as well as for the expression or mood of the interior as a whole. For example, if a row of columns or pilasters be of high brightness as contrasted with a dark background they will appear more massive than when they are in deep shadow against a bright background. Innumerable effects of light and shade are visible on every hand. Notwithstanding this fact the author is perhaps the first to attempt to formulate the science of light and shade and to relate it to the art.
The decorator arranges his values in an in terior just as a painter would in a landscape or other scene, but these values do not depend alone upon his pigments for they must borrow light and reflect it in order to be effective. Therefore the relative values of the different areas in an interior depend also upon the inten sities of illumination. But usually the decorator and the lighting specialist work independently and the final effect is not that which either had contemplated. It is a compromise depend ing upon the relative effectiveness of the illumi nation intensities and of the pigments. The decorator usually decides upon his values in the daytime and the distribution of light is playing a part in the values which he chooses for the various areas. The lighting specialist who installs the artificial lighting provides a radically different distribution of light with the result that it is not always harmonious.
The stage presents a picture in light, shade and color. Here more than in any other activity is lighting used for its expressive value. But bound by tradition and prejudice and handi capped by lack of familiarity with the simple laws of light and shade, the stage picture is full of incongruities and even grotesque effects. The footlights, common to the theatre, produce unnatural expressions of the human face as well as of the entire scenes. Throughout the ages during which the prejudices and artistic tastes of mankind have been formulated, dominant light from below the horizontal has never been a factor. The effects which it produces are un natural and have no logical place in the stage picture excepting for unusual purposes. The
footlights are of value in contributing, along with the borders and sidelights, a dim of light for illuminating the shadows but there is an opportunity for someone to come forth with a combination of architecture and lighting in the theatre which will produce artistic light and shade effects. The possiblities in such ef fects range from a concentration of light to a flood of it and from a picture in silhouette against a bright background to the reversed ef fect of a bright picture against a dark back ground. The modernists in the theatre are striving to eliminate such incongruities as the grotesque effect of footlights, the conflict of painted and real shadows and perspective. Not long ago a stage-setting often consisted of mea gre furnishings and all kinds of objects and shadows were painted upon the enclosing scenery. The painted shadows were usually in congruous with the real shadows and the perspective could not be correct from all view poinfs. Later some producers introduced fur nishings in great detail which have the advan tage of real shadows but may be criticized from many viewpoints, the chief one perhaps being the distraction from the drama itself. In the modern theatre the aim is to produce harmony of action, lighting and setting with the drama and this appears best brought about by sim plicity in lighting and in setting. This is accomplished by proper light and shade (also color) effects and by real shadows; in fact by utilizing the language of light, shade and color, The skeleton of any picture is its values or distribution of light and shade. Painting is an imitative art which depends upon pigments but the limitations of these are a great handicap to the artist. The greatest range of contrast on an artist's palette is represented by white and but the latter is never a total absorber of light, and white is merely a relative term. The amount of light reflected by the best white pigment is about 90 per cent and the purest black pigment ordinarily found among commer cial pigments reflects several per cent of the incident light. Therefore the ordinary range of contrast in brightness which the artist is able to command is about 30 to 1; that is, his white is only 30 times brighter than his black under equal intensities of illumination. With these he must represent the extreme range of values in a landscape in which the sky is com monly hundreds and even thousands of times brighter than the deepest shadow. This is one of the reasons why the artist must resort to illusions in imitating nature. In photography' the same difficulties are met and when the sci entific facts are realized it is quite wonderful that the painter and photographer are able to satisfy us with their products. 'Phis approaches the psychological aspect of light and shade and we must conclude that the imagination of the observer supplies much that is missing in the painting or in the photograph. In fact it is perhaps true that nearly all that we experience in viewing such a work of art we must supply. The work of art is merely an object which taps the imagination of the observer and by associa tions, memories and imagination he is capable of putting into the picture that which he de sires. Of course this does not apply to the aesthetic value of the picture which arises from its own harmony of parts, its rhythm and its grace of line. A simple example of interest from the psychological aspect is the appearance of a white hemispherical cup lighted by a source of fairly large solid angle. If the sur roundings are such that no inkling of the posi tion of the light-source is possible, this object will invariably be taken for a hemispherical solid lighted from a source exactly opposite to the actual position of the source. It is called a hemispherical solid or even a sphere because the light and shade distribution is similar but reversed and because these objects are more commonly encountered than the hemispherical cup.