Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing

by Laura J. Snyder

  And Drebbel was, let us remember, the foremost inventor of the day. He was probably the first to invent the microscope. He devised numerous clever and original instruments—even a working underwater ship or diving bell. Once lenses of a good enough quality were available, all the theoretical knowledge and practical requirements were ready for putting the camera obscura setup inside a box. In a sense, the only thing new was the wooden structure; conceptually, this was not a far leap from Risner’s hut, or even from the description of the camera obscura in Della Porta’s widely read Magia naturalis. The optics of the box-type camera obscura were the same as those of the room-type camera; it would be a simple matter of shrinking the room down to a small chamber and constructing it in wood.

  Lenses of the correct size and quality for such a use certainly existed by the 1620s. The lens for a camera obscura does not need to be as high in quality as a telescope lens, though it must be higher in quality than a spectacle lens. In the case of spectacles, the eye makes use of only a small part of the surface of the lens, and the eye’s power of accommodation (or adjusting) ensures that the object being viewed stays in focus even when the eye is seeing it from another direction, through a part of the lens with relative asphericity. With the lens of a camera obscura, however, every part of the lens is used to produce an image. So the quality of the glass and its polishing matters more than in spectacles: asphericity, inhomogeneity, bubbles, and other flaws will all reduce the quality of the projected images. However, since the camera obscura was not intended to greatly magnify the image, lenses as fine as those used in telescopes were not necessary. What was needed, basically, was a lens that would project the image of a relatively close object on a projection surface—either a wall, a canvas, or a plate inside a box-type camera—and to make the projection as large and bright as possible. The lens must have a fairly large diameter and a large aperture ratio to generate a large, bright projection. For a life-size projection the lens should have a diameter of about a foot. By 1604 Kepler had reported seeing a room-type camera obscura with a lens a foot in diameter in Dresden, but it is unknown how clear the image was; it is thought that lenses so large at the time had many irregularities, and would not have cast an exceptional image. Box-type camera obscuras, which projected a smaller image, would require smaller lenses, even as small as an inch or two in diameter, and these existed, at a high enough quality, by the early 1600s. There is no reason, then, to doubt that box-type camera obscuras existed by 1622.

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  By the mid-seventeenth century, the concept of the camera obscura, and room-type camera obscuras, had been known for centuries, tent-like camera obscuras were being used already for artistic purposes, especially in surveying and mapmaking, and box-type camera obscuras were available. Various authors were recommending the use of the camera obscura to artists. Writers on the camera obscura from Barbaro to Huygens, and later Van Hoogstraten, all expressed the view that the camera obscura displayed more than what could be seen with the naked eye; the camera also revealed something about nature and how it operated. In particular, it revealed optical laws, the way light works. As Huygens would declare, the camera was “one of the best optical experiments.” The camera obscura allowed the viewer to perceive truths of nature that were otherwise unseen.

  This ability of the camera obscura to observe more than what appeared to the naked eye was of special interest at the time. It was an empirical age, in which there was a nearly universal interest in making careful and numerous observations of natural phenomena in order to learn something about the underlying laws organizing them. Science had seen an increasing emphasis on observing phenomena carefully and using that data to infer laws of nature, as opposed to drawing conclusions about laws from what was written in ancient texts. Laws of nature, being universal, are inherently unobservable—we cannot observe all instances of a universal—and often involve unobservable causes. The new astronomers, like Galileo and Kepler, made and employed careful observations of heavenly bodies to conclude that the cosmos was not at all like Aristotle’s depiction of it. Francis Bacon was urging all natural philosophers to conduct experiments before drawing their conclusions. “Dig a pit upon the sea-shore,” he exhorted in the first line of his Sylva sylvarum, in order to study the percolation of water through sand. That book contained 1,000 suggested experiments, divided into 10 “centuries,” or groupings of 100, giving the natural philosopher much to do.

  But it wasn’t only the astronomers and other scientific men who were taking an empirical outlook—this philosophy permeated Dutch society. Wealthy traders and ordinary citizens created enormous cabinets of curiosity filled with specimens from all over the globe, testifying to their belief in the power of observing instances. Shells, stones, insects, antiquities, skeletons, even human body parts—collections like these graced the homes of many middle-class Dutch families. Swammerdam, who would later make groundbreaking observations with a microscope, was reputed to have the most splendid cabinet in all the land; the duke of Tuscany offered him 12,000 guilders (about $97,500 today)—a king’s ransom—but the offer stipulated that Swammerdam accompany the collection to Tuscany and remain to oversee it, so even though he was in desperate need of money, Swammerdam had to refuse. His father also had an enormous cabinet; it filled an entire floor of his home in Amsterdam and contained more than three thousand specimens, including the eggs of unusual species, aborted fetuses in jars, fossils, the skin of a seventeen-foot snake, as well as artifacts like Chinese porcelain and ancient Roman coins. Leeuwenhoek, too, would eventually compile a cabinet of curiosity of sorts, comprising samples taken from his own body, as well as specimens of canal water and rainwater, parts of animals and plants, and the bodily fluids and discarded hair and nails of his family members, friends, and neighbors. (Each sample was preserved with a particular microscope, the one most suited to observing it.) Medical doctors began performing public dissections in huge anatomical theaters, discovering—and demonstrating to crowds of citizens—the inner workings of the human and animal body. Mapmakers used the observations of men exploring the globe to produce ever-improved charts of the sea and land. Surveyors measured and mapped the land, often with the help of camera obscuras, just as astronomers were mapping the skies with the use of telescopes. Alchemists were using known principles of chemistry and trial and error to try to discover substances that could turn base metals into gold and silver.

  Artists also believed that their endeavors were founded on empirical processes. Especially starting in the 1650s, younger artists in the Dutch Republic held that painting must begin with direct observation of the world. This was a shift from earlier views of art, in which even landscapes were painted with more imagination than visual evidence. Landscape and seascape painters in the Dutch Republic began to go outside to paint directly from nature or from sketches made of observed aspects of a landscape. Still-life painters examined flowers, fruits, even insects carefully with magnifying lenses. Painters of genre scenes and portraits, too, were observing their models and their settings more closely.

  One of the main motivations for Dutch painting in the seventeenth century was a curiosity about the natural world, as it was accessible through the sense of sight. Indeed, one can say the subject of painting became sight itself. Whether a seascape, a landscape, a still life or a genre scene, a painting proclaimed, “This is what is seen.” That declaration had an associated value judgment: “And that is good, and it is enough.” No longer did a picture need to tell a story, as it had in the Italian narrative tradition. It was enough to describe what was observed.

  As Van Hoogstraten, writing in the 1660s, would remind painters, their object was to create “a truly natural painting.” Nature as it appeared to them—not an idealized or sentimental conception of nature—was to be the guide. Galileo had noted earlier that he preferred painting to sculpture, on the grounds that sculptors “imitate things as they are, and painters as they appear.” Such thinking led to the seventeenth-century expressive naturalism
seen in Fabritius’s The Sentry, where the viewer seems to be standing right over the corner of space inhabited by the sleeping guard, and in De Hooch’s views of courtyards in Delft. The viewer of De Hooch’s courtyards feels as if he or she had just left Emanuel de Witte’s church on the way home, and turned into a little street off the Market Square. Van Hoogstraten cautioned that to create a natural painting, it was not enough to observe casually: the artist must be an investigator of the visible world. Like the natural philosophers—who turned to telescopes and microscopes—painters, especially in Delft, were eager to avail themselves of optical aids to help them understand and represent nature as it appears.

  And yet, as Van Hoogstraten explained further, “a painter, whose work is to fool the sense of sight, also must have so much understanding of the nature of things that he thoroughly understands the means by which the eye is deceived.” Nature as it appears was understood to be different from nature as it really exists. Dutch Golden Age painting is often associated with a heightened realism, but in some ways it was a kind of illusionism, in which the painter’s knowledge of how nature looks to us was deployed to fool the eye in various ways. In 1604 Karel van Mander praised Hans Holbein’s portrait of Henry VIII as being so thoroughly alive (“soo gheheel levendigh”) that its head and body appeared to move, frightening those who saw it. A century later Arnold Houbraken remarked of a Rembrandt portrait that the head seemed to come out of the frame to speak to you. Art is a mirror of nature, Van Hoogstraten would say, a mirror for “making things that are not appear to be, and deceiving in a permissible, diverting and commendable way.”

  A picture shows us something that is not, in fact, before us; in that sense it intrinsically makes things that are not there appear to be there. In his own pictures Van Hoogstraten had used the pictorial device of the feigned frame in order to bring the viewer’s attention to the illusionism inherent in realist painting, the way that the painter simultaneously simulates and dissimulates. Some of the Delft church painters incorporated into their pictures a curtain on a rod, pulled over to one side, to draw attention to the fact that these were pictures—because paintings sometimes were hung on walls behind a curtain, to protect them from dust and sunlight. (Vermeer would use this device as well, for instance, in his The Reader [The Letter Reader].) The artist was encouraged to create deceptions of the eye (bedriegertjes) to fool the viewer into thinking that he is looking at visible nature, when he is really viewing a flat canvas. Like the drops of “dew” on the Verelst painting owned by Pepys, or the shadows of nails in the wall placed in the upper left corner of Vermeer’s Milkmaid, or the missing chip of paint on the wall behind the bird in Fabritius’s Goldfinch, the Dutch painter fooled the eye into thinking that what was made of paint on a flat surface was really a natural, three-dimensional thing. Dutch theorists and artists used the term houding as a blanket term for the many strategies that could be combined to create a compelling mimetic or imitative picture. The use of such strategies could “transform a painter’s imagination into a make-believe space” that looked, in the words of one of Van Hoogstraten’s fellow Dutch art theorists, “as if it were accessible with one’s feet.” Van Hoogstraten had seen a camera obscura at the Jesuit College in Vienna, where he viewed “countless people strolling and turning about on a piece of paper in a small room,” and one of his clients was Emperor Ferdinand III, who was known to take a special interest in the optical device. Van Hoogstraten had also observed a camera obscura in London, where he “saw hundreds of little barges with passengers and the whole river, landscape, and sky on a wall, and everything that was capable of moving was moving!” He most likely used the instrument in painting at least one of his works, View of the Hofburg in Vienna (1652). By the time he wrote the Inleyding, he had come to believe that the camera obscura could help the young artist more closely observe nature, and to learn more fully how it appears to us. “I am certain,” Van Hoogstraten confidently wrote, “that vision from these reflections in the dark can give no small light to the sight of the young artists; because besides gaining knowledge of nature, so one sees here what main or general [characteristics] should belong to a truly natural painting.”

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  At this moment the time was ripe for the use by Dutch artists not only of mirrors and lenses but also of camera obscuras. However, there was a long tradition of disparaging the painter’s use of optical and mechanical devices. In the early sixteenth century Leonardo da Vinci had scoffed at the pervasiveness of Alberti’s veils. “There are some who look at the things produced by nature through glass, or other surfaces or transparent veils,” he said. “They trace outlines on the surface of the transparent medium.… But such an invention is to be condemned in those who do not know how to portray things without it, nor how to reason about nature with their minds.” Although Leonardo had devised his own method similar to the Alberti veil to help students learn to draw the poses of models, he believed that after such training painters should be able to produce their pictures without them.

  The Paduan humanist Pomponius Gauricus, in his 1504 treatise on sculpture, told a “well-known story,” illustrating the same point, about a young acolyte who wished to see the “abacus” of Donatello—the device by which the sculptor was able to control the mathematical proportions of his works. Donatello is said to have replied, “I have no other calculator than that which I always carry without fail amongst my belongings.” He urged the young man to bring him a piece of paper, promising to demonstrate this calculator to him. When the student supplied the paper, Donatello simply sketched nude and clothed figures. As Michelangelo would say later in the sixteenth century, the painter should have compasses in his eyes, not in his hands. The science of art, he believed, should be so incorporated into the painter’s very being that he or she can deploy it without explicit thought.

  In the seventeenth century, however, especially in the Dutch Republic, the idea of what it meant to have instruments in the eye had changed. Empirical studies of the structure of the eye had overturned the old theories of vision. First, it was shown that the organ of vision was not, as it had previously been assumed to be, a lenticular organ filled with viscous fluid in the center of the eye, known as the “crystalline” or “glacial humor.” It was, rather, a lens located in the front part of the eye, one that would, like all lenses, invert the image it projected onto the retina at the back of the eye. To better understand the eye, Kepler had used the camera obscura as a model, arguing that the eye functioned like the optical device: with a lens receiving light rays from outside, focusing and projecting these rays onto the retina, which functioned as a “screen” for an inverted image. The eye, then, was a picture-making optical instrument. It is no accident that, discussing the way that all rays from one point formed an image on the retina, Kepler used the term pencilli, which referred to the artist’s brushes. To Kepler, the image on the retina was painted by a brush, just as was the artist’s picture. As he put it, “the retina is painted with the colored rays of visible things.”

  Earlier, Leonardo had been fascinated by the notion of the eye as an instrument and was the first to propose the camera obscura—not the version with a lens, but the one with a pinhole—as its model. Galileo’s friend Cigoli had compared the eye to a camera obscura with a lens in his Prospettiva pratica. Indeed, the eye had been compared to an optical device as early as the eleventh century, when the Persian polymath Avicenna compared it to a mirror: “The eye is like a mirror, and the visible object is like the thing reflected in the mirror.” The comparison of the eye to a camera obscura, which soon became widespread, was in step with the mechanistic anatomy of the day: William Harvey was using hydraulic machines as models of blood circulation, and Descartes modeled muscle contraction on pneumatic systems. Why not model the eye on yet another device?

  Knowing that people would be skeptical about the idea of an inverted image on the retina—after all, we do not see things upside down—Kepler and, later, Descartes described an experiment with a dis
sected eye that would show the retinal image to be inverted. By peeling off the outer membranes of the eye and replacing them with an artificial screen, the retinal images formed at the back of the eye could be observed. Descartes rather gruesomely suggested that the experimenter “take the eye of a newly deceased man or, failing that, an ox or some other large animal; carefully cut away the three enveloping membranes at the back, so as to expose a large part of the humour without shedding any; then cover the hole with some white body, thin enough to let daylight through, for example a piece of paper or eggshell.” This deconstructed eye should be put in the opening of a window so that the front of it faced objects outside lit by the sun, and the back (with the eggshell or paper) faced the dark room. The only light entering the room would be through the eye. “If you now look at the white [paper or eggshell],” Descartes instructed, “you will see, I dare say with surprise and pleasure, a picture representing in natural perspective all the objects outside.”

  In 1625 the astronomer Christoph Scheiner described how, in Rome, he had carefully removed the backs of the eyes of freshly dead oxen in order to observe the image formation on the retina. By 1663 Robert Boyle could gleefully report having demonstrated the inverted retinal image in human eyes: “Something of this kind we have also shown our friends with eyes of dead Men, carefully sever’d from their heads.”

  Leeuwenhoek would later perform a similar experiment on the tiny eye of the dragonfly. He separated the cornea and found that it was made up of six-sided parts, each forming a segment of a sphere. He viewed a lit candle through the cornea and was able to see through it the steeple of the Nieuwe Kerk, multiplied by the number of parts of the cornea, each tiny image inverted. Performing the same experiment with the eye of a “small fish,” he was able to see the inverted image of the street, and could even distinguish the colors of the clothing worn by passersby. Such experiments showed that the eye was indeed like a camera obscura.