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Already by 1623 Huygens could assume that all painters—indeed, most educated people—had heard about the camera obscura. Nevertheless, today the history of the camera obscura is not as clear and sharp as the images it can project. In part that is because the optical concept of a “camera obscura” existed even before there were any actual physical camera obscuras, and because actual camera obscuras existed even before they were called camera obscuras.
The concept of the camera obscura was useful in the early days of optical science because it illustrates a basic principle of optics, namely that rays of light, which move in straight lines, will, when passing through a small aperture, cross and reemerge on the other side in a divergent configuration; if a flat screen is placed in such a way as to intercept the path of the light rays after passing through the aperture, an image of what is on the other side of the hole will be formed on the screen. This image, though, will be reversed (as in a mirror) and inverted (upside down). In order for the image to be adequately visible, the screen must be placed in a room or box in which the level of light is lower than the light around the object.
As far back as the fifth century BCE, the Chinese writer Mo Ti recorded the creation of an inverted image when light passed through a pinhole in a screen. He referred to the place the inverted image occurred as a “collecting place” or a “locked treasure room.” Later, sometime after the third century BCE, Greek writers observed a natural occurrence of the camera obscura effect. During a solar eclipse, they noted, if the light falls through small holes in leaves, the image of the sun’s crescent is visible on the ground. This passage identified the basic theoretical concept of the camera obscura: the formation of an image through an aperture, in this case small holes found in nature. The ninth-century Chinese writer Tuan Cheng-shih discussed an inverted image of a pagoda being formed through a small hole he had made in a screen, but incorrectly explained the inversion, attributing it to reflections from the nearby sea. Another writer, Shen Kua, correctly explained the inversion by comparing the light rays to an oar in its oarlock: when the handle is up, the blade of the oar is down, and vice versa. In the tenth century Yu Chao-Lung constructed models of pagodas and projected their inverted image through an aperture onto a screen.
The eleventh-century Arab writer on optics Alhazen described his experiments with image formation through pinhole apertures in his book Perpectiva, using the term locum obscurum (dark place). He arranged three candles in a row and set up a screen with a small hole between them and the wall. He observed that the candle to the right of the hole made an image on the left of the wall, and vice versa. He did not mention that the images were inverted. He noted that images were formed only when there was a very small hole in the screen; when he tried larger holes, all that was produced on the wall was a round patch of light. In a discussion on “the shape of the eclipse,” Alhazen argued that a partially eclipsed sun will project a crescent-shaped image on a screen if its light passes through a round aperture.
New uses for the camera obscura were devised in the thirteenth century. Arnaud de Villeneuve arranged for players to enact a violent scene in an area of bright sunshine outside a darkened room. A small hole was made in the shutter facing the scene, which was projected onto a white sheet hanging opposite the hole. He hired other actors to stand just outside the window loudly imitating the sounds of men fighting and dying. A later writer described such spectacles, noting with satisfaction, “The spectators that see not the sheet, will see the image hanging in the middle of the air, very clear, not without fear and terror.” This was the medieval version of a movie theater.
Also in the thirteenth century, Roger Bacon followed up on Alhazen’s discussion by explicitly recommending the use of the camera obscura for making astronomical observations of the sun. This was an important development in astronomy, because natural philosophers could become blind temporarily—sometimes even permanently—after staring directly at the sun to observe solar eclipses or sunspots. John Greaves, professor of astronomy at Oxford in the sixteenth century, made a common complaint after measuring the sun’s diameter: “For some days after, to that eye with which I had observed, there appeared, as it were, a company of crows flying together in the air at a good distance.” For safer observations of the sun, one could make a small hole in a closed shutter, through which light from the sun outside would pass. On the wall opposite the hole, an inverted image of the eclipsing sun would be projected and could be watched safely. In 1292 Guillaume de Saint-Cloud described how he had used a setup like this one to observe the solar eclipse of 1285. But it is not until the sixteenth century that we find a published illustration of a room-type camera obscura being used for observing a solar eclipse. This was also the first published illustration of an actual camera obscura setup, as opposed to a merely theoretical drawing of the camera obscura principle showing rays intersecting after passing through a hole and then ending up on a flat surface.
The solar eclipse of January 1544 was observed by the Dutch mathematician and physician Reinerus Gemma Frisius (also known simply as Gemma Frisius), whose book De radio astronomico et geometrico (1545) contains the image of a solar eclipse projected onto the wall of a room by a pinhole in the shutter. The drawing shows the inverted and reversed image of the sun projected on the wall opposite the small hole in a window shutter. Later Copernicus, Tycho Brahe, Johannes Kepler, and others used this kind of room-type camera obscura. To observe sunspots, Galileo used a telescope as a compound lens to project the image of the sun on the wall of a darkened room.
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In order for the camera obscura to be useful to artists, however, another innovation was required: the use of a lens in place of the small aperture. The first to suggest this in print was the sixteenth-century Venetian architect Daniele Barbaro. In his La pratica della perspettiva (The practice of perspective, 1569), a book written specifically for artists, Barbaro published a detailed description of the camera obscura, calling it “a most beautiful experiment concerning perspective.” He instructed his readers to “make a hole of the size of a spectacle lens in the window shutter of a window of a room from which you wish to observe. Then take a lens from spectacles used by old men [i.e., a convex lens] and fix this lens in the hole you made.” Next, he advised, close up all the windows and doors of the room so that the only light entering the chamber comes through the lens. Then “take a sheet of paper and hold it behind the lens.… By moving the sheet of paper towards or away from the lens you will find the most suitable position.”
Given his suggestion of moving a sheet of paper closer to and farther from the lens in order to find the optimal focus, it is likely that Barbaro was not just imagining a new way to construct a camera obscura but had actually built one like this. He also proposed the addition of a diaphragm, a small aperture placed behind the lens to decrease the light passing through it, and in this way increase the brightness of the image. Actually, it was sharper, not brighter—the diaphragm prevented spherical aberration by blocking all the light except that passing through the center of the lens. But this would make the image seem brighter. The fact that Barbaro takes no credit for these two innovations, the lens and the diaphragm—introducing them in the book as if everyone knew about them—may mean that they were already known when he wrote. Convex lenses, as we saw, had been being used in spectacles since the end of the thirteenth century, so in some ways it is surprising that it took over two centuries before anyone thought of adding a lens to the camera obscura. But it was probably not until around Barbaro’s time that the lenses being produced were capable of projecting an image.
Once a lens and a diaphragm were introduced into the camera obscura, the image became clearer and brighter, and numerous writers began to mention the usefulness of the device to artists. Barbaro himself suggested that the camera obscura could be employed for making exact copies of maps by projecting and tracing the images. (The discussion of the camera obscura appears in a section of his book on mechanical
drawing devices.) Others had proposed the artistic use of a camera obscura before this—for instance, in 1521 Cesare Cesariano had noted that the camera obscura would be excellent for “painters, astronomers, and opticians [those who study optics].” And astronomers were already tracing the solar image projected by a camera obscura, so it was not a stretch for this use to be taken up by artists as well. Reinerus Gemma Frisius mentioned marking with a pencil the diameter of the sun as projected by the camera obscura. Christoph Scheiner claimed to have observed, and sketched, sunspots in 1612 by projecting the image through a telescope onto a tablet below. He included drawings made with the device in his Rosa ursina, published in 1630.*2
Soon another improvement in the design of the camera obscura was introduced: the use of a mirror to correct the reversal and inversion of the image. If a mirror was placed at a 45-degree angle to the light before it was projected onto the wall, it would correct the inversion and reversion of the image. The use of a mirror was suggested in a manuscript by the Venetian Ettore Ausonio (1520–70), and later in a book by Giovanni Battista Benedetti published in 1585. Around this time English mathematicians were also talking about the combination of a lens and a mirror for projecting images in a camera obscura; John Dee, Thomas Diggs, and William Bourne all mention this setup and its application for making the drawings used to create maps.
Although the additions of a lens and a mirror to the camera obscura setup had been mentioned earlier, they were widely publicized by the discussion of camera obscuras in the twenty-volume second edition of Della Porta’s Magia naturalis (1589). Della Porta was a showman, natural philosopher, and wizard, whose dabbling in magic led to his investigation by the Inquisition. He founded a secret society in his hometown in Naples, called I Segreti, whose members were instructed to “discover a secret unknown to the rest of mankind.” These secrets, collected in his book, included methods for removing warts, curing baldness, and countering armpit odor. Della Porta, who wrote sixteen other books, became so renowned that it was said the two greatest tourist attractions in the Naples of his day were the baths of Pozzuoli and Giovanbattista Della Porta.
Like earlier writers, Della Porta highlighted the value of the camera obscura to painters, especially when a lens was added to the device to make the image clearer. He exhorted, “One that is skilled in painting, must lay on color where they [the colors] are on the table, and shall describe the manner of the countenance, so the image being removed, the picture will remain on the table.” He believed that the camera obscura, besides being useful for painters, was a model for studying optics and a way of exploiting natural phenomena to astonish and entertain, like Villaneuve’s theaters. Della Porta’s book was published in a Dutch edition (as well as Latin, Italian, and French editions) in the sixteenth century, so with the publication of his book knowledge of the camera obscura using a lens and a mirror became widespread.
The first to propose a smaller, portable camera obscura seems to have been the German mathematician Friedrich Risner, who held the first chair of mathematics at the Collège Royale de France. In his edition of the works of Alhazen and Witelo, published in 1572, Risner proposed a lightweight wooden hut that could be carried on two rails—like a litter used to transport royalty—to any desired location for the purpose of creating topographical drawings. This large box would be fitted with lenses on each of the four sides, with a cube of paper placed in the middle. A man would go inside the box and trace the images being projected through each of the four lenses onto the sides of the cube.
Johannes Kepler would soon invent another version of this portable hut: a tentlike camera obscura, which could be set up anywhere one wished outdoors and which projected an image of the outside scene onto a sheet of paper inside the tent. Kepler himself had coined the term “camera obscura,” employing it for the first time in his 1611 book Dioptrice. Kepler used the term while describing the solution to the problem of “paint[ing] visible objects on a white wall with a convex lens.”
Kepler had learned how to use the camera obscura for astronomical purposes from Michael Mastlin at the University of Tübingen. In July of 1590, Mastlin had taken his students—including Kepler—onto the roof of the town’s cathedral to teach them how to observe and record a solar eclipse. Through a small aperture in the roof, the image of the sun fell onto a white tablet below; Mastlin had his students safely observe the progress of the eclipse and calculate the diameters of the sun and the moon. Kepler remembered this experience and later used it to invent a camera obscura that could be used out “in the field” for making drawings for maps or topological studies.
The English diplomat Sir Henry Wotton, who met Kepler in Linz in 1620, excitedly wrote to Francis Bacon, the natural philosopher and politician, to tell him about this new invention. Wotton had learned about it after complimenting Kepler on a drawing in Kepler’s house. Kepler admitted that he had done it himself, adding with a sly smile, “non tanquam pictor, sed tanquam mathematicus” (not as a painter, but as a mathematician). This answer, Wotton said, “set me on fire,” and he pressed Kepler until he told him his secret. As Wotton revealed to Bacon, Kepler had devised a small black tent that was completely closed off except for a small hole, to which he attached a telescope. The image of the landscape outside the tent was projected onto a piece of paper inside the tent. To sketch a 360-degree panorama, Kepler rotated the tent on its stand by degrees, till he had painted the whole aspect of the field—a “true portrait” of an entire territory, as Wotton put it. Wotton told Bacon that in his opinion, the device would be most useful for “chorography” (mapping and surveying). While he acknowledged that it could be used by artists, he felt that their reliance on the device would be “illiberal,” though he admitted that no artist drawing without the device could do so as “precisely.” Wotton, who had lived in The Hague when he was the English ambassador, would surely have shared the news of this innovation with his friend and former neighbor Constantijn Huygens.
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At this point in the history of the camera obscura, things get hazy. By 1572 the room-type camera obscura had already been shrunk down to a small, portable room, which can be thought of, after all, as a very large box. However, when pinpointing the first appearance of box-type camera obscuras—devices in which the lens, the mirror, and the screen on which the image was projected were put inside a small wooden box—most writers date it to around the mid-seventeenth century, nearly a hundred years later. Gaspar Schott described a small, portable camera obscura in his Magia universalis in 1657, and in 1669 the British natural philosopher Robert Boyle depicted a box-type camera he claimed to have constructed “severall years ago.” Boyle wrote to the Royal Society of London,
I need not perhaps tell you, that if a pretty large Box be contrived, that there may be towards the one end of it a fine sheet of Paper stretch’d like the Leather of a Drum-head at a convenient distance from the remoter end; where there is to be left an hole covered with a Lenticular Glasse fitted for the purpose, you may at a little hole, left at the upper part of the Box, see upon the Paper such a lively representation; not only of the Motions but shapes and Colours of outward Objects, as did not a little delight me, when I first caused this portable darkened Roome, if I may so call it, to be made.
Johann Zahn illustrated several types of small box-type camera obscuras in a book published in 1685, and Hooke is thought to have devised a portable one around the same time.
I believe, however, that the type of camera obscura Huygens purchased from Drebbel in London and brought back with him to The Hague was a box-type device, which means that the existence of box-type camera obscuras dates back at least to 1622. Huygens had mentioned to his parents in a letter from England, “I have at home Drebbel’s other instrument, which certainly makes admirable effects in painting.” In his autobiography, written in the late 1620s (only a few years after the events he related there), Huygens tells us that he brought back a camera obscura from Drebbel, that it was a “constructed instrument” with
the ability to focus the image by “the placing of the movement, the pushing of it forwards and backwards and the easy turning to all sides,” that he had been using it to paint, and that he demonstrated it to his guests at his father’s house. So there must have been something physical that he brought back with him, not just, say, the technique for putting a hole in his window shutter to form a room-type camera obscura. In his report of the demonstration, Huygens described the device as something that has a bright plate or panel in an enclosed space, which the Latin makes clear is the enclosed space “of the plate,” which means a box surrounding the plate, not an enclosed space of a room. The “pushing” forward and backward sounds very much like the focusing of the tube holding the lens, as in the microscopes that Drebbel was constructing around the same time. Huygens also noted that Drebbel had a way to correct the inversion of the image in the camera obscura, so he presumably had invented a box-type reflex camera obscura, one with a mirror placed to revert the image.
Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing Page 15