Light in our lives Physics World  March 2015
(Abelardo Morell / Edwynn Houk Gallery, New York)

Rooms with a view

Sidney Perkowitz explains how the camera obscura (“dark room”) and camera lucida (“luminous room”) are still relevant today in science and art, despite the availability of much more modern cameras

When you tap your smartphone to take a selfie, you’re using a compact miracle of the latest optical and digital technology.

It is easy to forget that until relatively recently, images were recorded very differently, using devices that needed no batteries and captured images on film. Yet before even conventional photography was invented in the mid-19th century, there were two other devices that people used to capture images: the camera obscura and the camera lucida.

The camera obscura was originally just a hole in the wall of a dark chamber. This simple set-up is reflected in its Latin name, which translates to “dark chamber” or “dark room”. The camera lucida, also a fairly simple device, is basically a prism mounted on a stand, and its name translates to “bright chamber” or “luminous room”. Both produce an image of a scene that an artist can trace.

Although imaging technology has advanced far beyond these methods, there are examples in science, art and technology where these are still the best tools for the job

Although image-capturing technology has since advanced far beyond these basic methods, there are examples today in science – including physics – as well as in art and technology, where these devices are still the best tools for the job.

The obscura’s artful history

The camera obscura and camera lucida may sound similar, but their origins show vastly different approaches to turning the laws of light into a device. The lucida was patented in 1807 by the English scientist William Hyde Wollaston, who cleverly used known optical technology to capture scenes on paper. The effect behind the obscura, in contrast, was first discovered in nature, and much earlier.

One of the first scholars to write about the obscura was Aristotle, way back in the fourth century BC. During a solar eclipse, Aristotle observed multiple images of the crescent Sun beneath a leafy tree. Each tiny space between the leaves acted as a pinhole-like opening, through which light rays from the partly eclipsed Sun travelled in straight lines to form an inverted image on the ground below. What was special about that day was the low background light level; although images are projected through natural pinholes all the time, it was only in the gloom of the eclipse that the dim images became visible.

As far as we know, Aristotle did not, however, figure out the principles behind the phenomenon. That had to wait until the 11th century AD when the Arab physicist and mathematician Ibn al-Haytham greatly advanced optical science by describing those laws. Based on his understanding of those principles, he was able to project an entire outdoor scene onto a screen with an obscura. (For a fictional account based on the known details of al-Haytham’s life – including his writing the seven-volume Kitab al-Manazir, or “Book of Optics” – see “The Scholar and the Caliph” from January 2011 in our digital collection “Select: Light 2015”.)

A helping hand? The exceptional architectural details of Venice in Canaletto’s work are due to his having used a camera obscura, some have argued. (Canaletto, c. 1730)

The development of the camera obscura did not stop there however. By the 15th century, darkened rooms with a small hole in the wall were being used to observe the Sun, while in the 16th century, the hole was replaced with a convex lens, which gave a brighter image due to the bigger aperture. In the 17th century the obscura was first made in the form of a portable box.

Artists both unknown and celebrated learned about the obscura. Leonardo da Vinci described one in his writings, while some used the obscura to trace the images that it projected onto paper in aid of their art, as the 18th century painter Canaletto is said to have done in creating his detailed views of Venice.

Once modern photography was developed in the 19th century, you might think the days of the camera obscura were numbered, but it has recently gained a surprising new lease on life. In 2001 in his book Secret Knowledge, the prominent British artist David Hockney presented his thesis that not only had artists such as Canaletto used the obscura for architectural landscapes, but so too had even highly revered portrait artists such as the 17th century Dutch painter Johannes Vermeer – whose works include Girl with a Pearl Earring. Later, such artists used the lucida as well for making art, Hockney claimed. Many in the art world viewed these assertions with horror, thinking that, if true, they would diminish the talents of gifted artists. The controversy led to a lively symposium at New York University in 2001, at which Hockney and other artists, art historians and optical scientists (including myself), cited artistic, historical and optical evidence for or against Hockney’s idea.

Light bulb Abelardo Morell photographed an artistic version of the ray-tracing diagram seen in every optics textbook that defines how a camera obscura or a modern camera forms an image. (Courtesy of Abelardo Morell and the Edwynn Houk Gallery, New York)

Correct or not, Hockney’s thesis evoked interest in the obscura, which survives today in museums such as San Francisco’s Exploratorium and London’s Science Museum, as well as in pinhole cameras, which add film to an obscura to capture the image. Most notably, the obscura thrives in the work of the Cuban–American photographer Abelardo Morell, who since 1991 has found ways to take photographs inside the dim interiors of room-sized camera obscuras. (He also photographed an artistic version of the ray-tracing diagram seen in every optics textbook that defines how a camera obscura or a modern camera forms an image – see image left.)

In Morell’s initial set-up, he would select an ordinary room with a striking view – usually a hotel room for practical reasons – cover its windows with black plastic sheeting and then poke a centimetre-sized hole in the plastic. After aiming a modern camera at the wall where the projected image faintly appeared, he would open the shutter and leave the room. Typically he had time for a meal, a movie and more, for an exposure took 8–10 hours with the film camera he first used. But when he returned, he would have captured a remarkable image – an inverted view of the outside superimposed on the bedroom wall.

Morell eventually replaced the film camera with a digital device, which sharply reduced exposure times, making it possible to capture images in colour and to record dynamic effects such as the motion of clouds. He also added a lens to sharpen the image and a prism to turn it right-side-up. For his most recent camera-obscura project, Morell constructed a “tent camera” – a portable room enabling him to set up anywhere. Rather than using a hotel room wall, the image is projected onto the natural ground under the tent – a feature Morell has embraced in his tent photos by artistically marrying images of the nearby landscape with those of the terrain below. In pushing the simple camera obscura to these limits, Morell’s work has won international recognition.

Caught on camera Photographer Abelardo Morell makes clever use of hotel rooms and even a tent (bottom images) as giant camera obscuras. (Courtesy of Abelardo Morell and the Edwynn Houk Gallery, New York)

Fast as lightning

More than anything, the camera obscura today is a fantastic demonstration in physics education as it so clearly shows the laws of optics – light travelling in straight lines through a small hole to project an inverted image. But its simple yet powerful design is also still relevant in contemporary physics research. Joseph Dwyer and colleagues at the Florida Institute of Technology have built a version that can image lightning – not the visible part of lightning that anyone can see or record with a regular camera, but the X-ray part of the electromagnetic spectrum that is invisible to the naked eye.

It had long been conjectured that thunderstorms produce X-rays, but only in 2001 did a group at the New Mexico Institute of Mining and Technology use X-ray detectors to show that it is specifically the lightning that does so. Two years later Dwyer and his group showed that artificially triggered lightning creates X-rays too. They did this by launching a rocket, which trails a copper wire, into a thundercloud. The wire conducts current to the ground, vaporizing as it does so, to produce a relatively well-defined lightning stroke.

X-ray vision Joseph Dwyer and his team built a camera obscura to photograph X-rays from lightning that they created with this rig. (Dustin Hill / International Center for Lightning Research and Testing)

To explore these X-rays, Dwyer decided to design a device that would not just detect them but photograph them too during a triggered lightning strike. The apparatus needed to respond to X-rays with energies up to mega-electronvolts within times of less than 1 μs, and it would have to ignore the abundant extraneous radiation that would otherwise swamp the image. The solution was what Dwyer called “a very old technique for making images” – a camera obscura on a massive scale; or, more properly, a pinhole camera with the means to record the image.

Dwyer’s X-ray camera is a metre-sized steel and aluminium box, clad in 550 kg of lead sheeting that blocks out X-rays and all other radiation except what enters through a circular “pinhole” 7.62 cm wide. This diameter is shared with each of 30 X-ray detectors, in which a scintillator converts X-ray photons into visible-light photons that are sensed by a photomultiplier tube. These units, arranged in an image plane, effectively form an X-ray film with a 30 pixel resolution. In 2010 the camera was used to obtain the first photos and movies of X-rays emitted by lightning. These media, which show the X-rays’ evolution in space and time, are now undergoing analysis to study the mechanism that makes the X-rays.

Seeing the light

The camera obscura, whether as a bulky X-ray camera or as an artist’s aid, has never been easy to use. For artists, and natural scientists who used it as an image projector in the field, it was the best tool available to help them accurately sketch some scene or object – but they had to work in semi-darkness and with an inverted image. Before modern cameras came along and made the need for sketching mostly redundant, these shortcomings were addressed with Wollaston’s invention of the camera lucida.

Wollaston had originally trained as a physician, but he turned to research after being rejected for a medical position in 1800. He did excellent work in physics, chemistry and optics, finding the first known amino acid, discovering the elements platinum and rhodium, and designing scientific instruments. But his most famous invention, the lucida, was inspired by his lack of artistic ability, which had kept him from accurately drawing geological features during an excursion in 1800 and even from simply amusing himself “with attempts to sketch various interesting views”. Wollaston’s frustration must have stimulated his mind, because by 1807 he had patented “an instrument whereby any person may draw in perspective”, which he named the camera lucida in contrast to the camera obscura.

With the eye properly positioned, the artist could see both his or her hand holding a pencil and the image of the scene

Wollaston’s design used a quadrilateral prism mounted on a vertical stand. The prism was cut at carefully determined angles so that light rays from a scene before it would enter, undergo two total internal reflections without leaving the prism and losing brightness, and finally emerge directed upwards. An artist looking straight down at the device would see the rays as if they had originated from an image of the scene laid out right-side-up on the table. That is an illusion, since nothing is really projected there; but with the eye properly positioned, the artist could see both his or her hand holding a pencil and the image of the scene, to then be traced onto paper.

Once the device became known, sales soared all over Europe as users realized how versatile it was: it could be used under full lighting, it produced an upright image and it could be carried around. One 19th century artist who used it to draw highly realistic portraits, according to Hockney, was Jean-Auguste-Dominique Ingres. Scientists also liked its suitability for the field. The English scientist John Herschel, son of astronomer William Herschel, was a prominent user. He drew botanical images with the lucida early in his career and also sketched scenic landscapes as he travelled.

Faithful portrayal Portraits by 19th century painter Jean-Auguste-Dominique Ingres may owe their realism to his use of a camera lucida. (Jean-Auguste-Dominique Ingres, 1821)

One variant of the lucida, invented in 1820, even made it possible to draw images as seen through a light microscope. In fact, even though modern microscopes can image objects with incredible resolution, this lucida sketching method remains valuable for scientists – having been used, for example, to draw the animal fossils from the Cambrian explosion of species over 500 million years ago that are preserved in the Burgess Shale in British Columbia, Canada. According to palaeontologist Jean-Bernard Caron at the Royal Ontario Museum, these drawings add something beyond photography, for they show “how the different parts [of a fossil] fit on top of each other…A photograph…will obviously be silent, and it is only through the interpretation of the worker that we are able to put the different parts together”. The technique has also been used in Nobel-prize-winning neuroscience research as well as in geology.

Despite its utility, to make a permanent recording the lucida still required its user to draw the picture it created. That inspired photographic pioneer William Henry Fox Talbot – who had been encouraged by his friend John Herschel to use the lucida in 1833 but found it unsatisfying – to seek an easier way to record an image. Talbot, with help from Herschel, began exploring methods to hold or “fix” an image on paper by chemical means. By the 1840s he and Louis Daguerre in France had announced true photographic processes. That began the long evolution that led first to superb film cameras, and then to the revolutionary technology that captures light pixel by silicon pixel, rather than molecule by chemical mole-cule, in a camera or smartphone.

Lucida revamped

But despite the technological superiority of digital and even film cameras, the camera lucida has recently come back into vogue, albeit in modern versions. Unsurprisingly, you can download an iPhone app to simulate the device by superimposing on the iPhone screen an image of what is seen through the phone’s camera – such as your hand holding a pen to paper – and an image on the phone such as a photo of a pet. More remarkably, the lucida still has strong hands-on appeal, as found by Pablo Garcia and Golan Levin, who practise and teach art at the School of the Art Institute of Chicago (SAIC) and the School of Art at Pittsburgh’s Carnegie Mellon University, respectively.

Garcia, who admires and collects camera lucidas, agrees with Hockney’s thesis. “It made perfect sense,” he says, “that the great artists would be deeply involved in technology, and not just contemporary media artists, but all artists through time. The lucida [was] pivotal in the early 19th century.” In 2012 he and Levin decided to create a 21st century version, partly as “a provocation, a ‘performance’ ” to demonstrate this significant link between art and technology. Using cash raised through the crowd-funding website Kickstarter, they developed what they dubbed the NeoLucida – a sleek and contemporary version of Wollaston’s device. The NeoLucida features aluminium construction, and a prism that yields a brighter image through another bit of optical physics: enhanced reflectivity from its mirrored surfaces.

Back in bloom The NeoLucida is a modern camera lucida device. (NeoLucida)

The device has proven incredibly popular. Instead of the 500 units Garcia and Levin anticipated would “get a small conversation going”, the two have been filling orders for some 20,000 NeoLucidas through Kickstarter, Amazon and now the Design Store of New York’s Museum of Modern Art – a particular stamp of approval for the device’s clean aesthetics and technology.

Still, there are limitations to early optical technology, as my experience with a NeoLucida demonstrates. It takes practice to learn how to position the eye to see the illusory image, and any movement of the head shifts it. Even when the image is clear, a good eye and a steady hand are needed to trace it artistically. But these difficulties in fact illustrate that a lucida or obscura is no effortless royal road to drawing mastery, and those who once used these aids in their art were nevertheless exercising their artistic abilities.

The simplicity of these two antique devices contrasts with the characteristic opacity of modern technology, whose inner workings we rarely see or grasp. The smooth curves of a smartphone or tablet hide the complex paths of the photons and electrons that carry a photograph into it or out to the Internet. But in the camera obscura and camera lucida, the simple physical rules of straight rays of light and their refraction or reflection are clearly expressed in air and glass, with results that scientists and artists can preserve through their own efforts and with their own interpretation.