Simultaneous Contrast

Included in Aristotle's book On Sense and the Sensible is a description of the three primary ways of mixing colors. One approach is to mix a quantity of one color of paint with a quantity of another color, producing a third, distinctive color of paint, ready to be applied to the painting surface. A second is to place a transparency of one color over an area of another color. In most cases, the transparency is accomplished by adding binder or diluent to the paint to disperse the particles of pigment. Light is then allowed to pass through the transparent layer to interact with the area of color beneath. Color signals from both the transparency and the underlying color mix as they are reflected to the eye, producing a third color sensation (see Section 5.5). The third way to mix colors is to intersperse many small areas (dots or small brushstrokes) of two different hues. Viewed from a distance, the small areas of color appear to blend together to form a third color. The mixing in this case is known as optical mixing. Signals from each color are transmitted simultaneously to the eye. The amount of optical mixing is dependent on the size of the individual areas of color (the small dots used in commercial color printing cannot be sensed as individual dots without magnification, for example).

Throughout the centuries, artists have benefited from their close association with the scientific community, incorporating for their own purposes developments in optics, chemistry, and physics. In the mid-nineteenth century scientific investigations into the fundamental properties of light and matter had a direct influence on the work of some of the most innovative artists of the period.

In 1839, the French chemist Michel-Eugène Chevreul published a book titled The Principles of Harmony and Contrast of Colors. Chevreul worked at the tapestry workshop Les Gobelins in the dyeing department. Here he carried out experiments with various dyes in an attempt to increase or alter the intensity of colors. Tapestries are made by weaving colored yarns together to form images. Masses of color, areas of modulation of color, gradations of value, are all made up of thousands of tiny loops of colored wool (Color Plate 14). They are essentially small single-color dots that, when carefully organized, mix at a distance to create the desired modulation. Because of the relatively small scale of the color dots, our eyes cannot perceive individual color sensations. The separate color signals merge, or optically mix, into larger areas of color, shape, and image.

Chevreul realized that optical mixing was not the only dynamic at work when colors were placed adjacent to one other. He found that by utilizing the phenomenon of simultaneous contrast, he could alter the perception of a color by the choice of adjacent colors. He could even increase the perceived saturation of a color. More could be done, in fact, through juxtaposition than through the development of new dye colors. One of the remarkable things about his discoveries was that the effects were predictable.

The Principles of Harmony and Contrast of Colors was directed as much to painters as it was to scientists and dyers of wool. Chevreul gave the advice to painters that they be observant of the effects of various kinds of light or shade on local color (the inherent color of an object) in the world around them. Although he seems to have been oriented toward a realist view of painting, that is, that the painter should faithfully replicate what is perceived in nature, he does suggest that some liberties be taken at times to accommodate an aesthetic ideal. It was the particular combination of his views on painting and observations on the perception of color that struck a chord with painters of his time.

Chevreul's work suggested to painters that color could be thought of as independent of the objects and elements of nature. One could see that by understanding the dynamics of simultaneous contrast, many of the perceptual functions within a painting that were performed by pictorial description (drawing), could be performed by color, or at least the use of color could reinforce other means of description. The illusion of space, for example, could be created simply by placing one color against another. One color could make an adjacent color appear more intense and therefore advance spatially toward the viewer. Because the principle of simultaneous contrast effects differences in value as well as hue, darks could be made to seem darker, and lights, lighter. These perceptual characteristics have offered the painter a much expanded visual vocabulary with which to construct paintings.

Perhaps the most dramatic manifestation of the laws of simultaneous contrast as described by Chevreul can be found in the work of the French painter Georges Seurat (Color Plate 15). Seurat applied dots of color in a nearly uniform distribution over the entire surface of the painting (sometimes even including the frame). Small brushstrokes of color (often fully saturated primary and secondary hues) were applied to the painting in combinations that served a number of functions. The combinations of

Fig. 4.6. Judith with the Head of Holophernes, Artemisia Gen-tileschi, c. 1625. Oil on canvas, Detroit Institute of Arts.

One of the more conventional ways to suggest luminosity in a painting is to offer clues to the viewer through images of light and their effects on the spaces and objects around them.

Fig. 4.6. Judith with the Head of Holophernes, Artemisia Gen-tileschi, c. 1625. Oil on canvas, Detroit Institute of Arts.

One of the more conventional ways to suggest luminosity in a painting is to offer clues to the viewer through images of light and their effects on the spaces and objects around them.

separate dots of color mix optically to produce in the eye the sensation of masses or gradations of more complex color. He mixed purple, for example, by distributing dots of red and blue evenly over the surface, sometimes layering the colors as well (Color Plate 16). Fully saturated as well as more complex and modulated colors were combined to produce in the eye a very full range of sensory response, from intense fields of dense, uniform color, to grayed, neutralized fields of color. The resulting color fields can be as simple as a fully saturated purple made of red and blue components, or as complex as a purplish-gray containing blue, pink, sienna, green, and yellow (Color Plate 17). Warm and cool colors could be combined in this way along with complementary colors to produce neutral or grayed tones. In the case of grayed optically mixed color, there is an undertone of intensity due to the presence of relatively saturated color. We see and understand the area as neutral, but we sense the intensity within it.

Another function of Seurat's technique was to produce the sensation of luminosity. Afterimages generated by the small dots of color produce the sensation of many small colored light sources distributed across the painting surface. The more traditional (and often as effective) approach is to suggest luminosity through depiction: The viewer senses the light conceptually as the mind accepts the image as a real experience as in Artemisia Gentileschi's Judith with the Head of Holophernes (Figure 4.6). A light source is given within the pictorial space of the painting, and its effect is clearly shown on the surfaces adjacent to it.

Not all painters place so much importance on the implication or representation of light in their work. However, the light that surrounds the work is of critical concern to all painters. It is the medium by which the color, image, message (in fact, nearly all that the painting has to offer) is transmitted to the eye of the viewer.

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Freehand Sketching An Introduction

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