This illustrates the pitiable weakness of pigments alone as representative media. Will not light _transmitted_ through media some day be utilized to overcome this inherent handicap of reflecting media? To what extent is the success of stained glass windows due to a lessening of this handicap? The range of brightness in this case may be represented by a black (non-transmitting) portion to the brightness of the background (artificial or sky) as seen through an area of clear glass. Transparencies have an inherent advantage over ordinary paintings in this respect and many effective results may be obtained with them even in photography. It is interesting to study the effect of greatly increasing the range of values or brightnesses in paintings by utilizing non-uniform distributions of light. Let us take a given landscape painting. If a light-source be so placed that it is close to the brighter areas (perhaps clouds and sky near the sun) it will illuminate this brighter portion several times more intensely than the more distant darker portions of the picture (foreground of trees, underbrush, deep shadows, etc.). The addition to the effectiveness of the illusion is quite perceptible. This effect of non-uniform lighting may be carried to the extreme for a painting by making a positive lantern-slide (rather contrasty) of the painting and projecting this slide upon the painting in accurate superposition. Now if the painting is illuminated solely by the "lantern-slide" the range of contrast or brightness will be enormously increased. The lightest portions of the picture will now be illuminated by light passing through the almost totally transparent portions of the slide and the darkest portions by light greatly reduced by passing through the nearly opaque portions of the slide. The original range of contrast in the painting, perhaps twenty to one, is now increased perhaps to more than a thousand to one. This demonstration will be surprising to anyone and will emphasize a very important point to the painter. The painter has at his disposal all the scientific facts of light, color, and vision. Many of these have been presented elsewhere,[9] and those pertaining to illusions have been discussed in preceding chapters. These need not be repeated here excepting a few for the purpose of reminding the reader of the wealth of material available to the painter and decorator. Many tricks may be interjected into the foreground for their effect upon the background and vice versa. For example, a branch of a tree drooping in the foreground apparently close to the observer, if done well, will give a remarkable depth to a painting. Modeling of form may be effected to some extent by a judicious use of the "retiring" and "advancing" colors. This is one way to obtain the illusion of depth.