An old idea with a long life
A camera obscura, Latin for dark chamber, is a darkened space with a small opening that projects an image of the outside scene onto a wall or screen inside. It is the oldest ancestor of the photographic camera, but its story does not end when photography begins. The device has been a scientific instrument, an artist’s aid, a Victorian entertainment and a modern attraction. This article follows that whole timeline, while the optics, the artists’ use and the portable versions are covered in more depth by separate articles.
Early descriptions
Written accounts of the effect appear in several cultures. Chinese texts associated with the philosopher Mozi, from around the fifth century BCE, are usually cited as an early record of an inverted image formed through a small hole. Greek writings, including works attributed to Aristotle, discuss why sunlight passing through gaps in foliage forms round or crescent-shaped spots during an eclipse. The eleventh-century scholar Ibn al-Haytham in Cairo made a more careful analysis, showing that the image is formed because light travels in straight lines. The Chinese scientist Shen Kuo wrote about the inverted image in the same century.
In medieval Europe, scholars including Roger Bacon discussed the phenomenon, and astronomers used dark rooms to watch the sun without being blinded. These uses are not always easy to date, and historians caution against assuming that every observation described a purpose-built device.
Renaissance and the viewing room
By around 1500, the camera obscura was being described in notebooks, including those of Leonardo da Vinci. In 1544, the Flemish scientist Gemma Frisius published an illustration of one used to observe a solar eclipse. In 1558, the Neapolitan writer Giambattista della Porta recommended it for drawing, and a few years later Daniel Barbaro described using a lens and an adjustable opening to improve the image. Johannes Kepler used the term camera obscura in the early 1600s and carried a portable tent version for sketching landscapes.
Printed books carried these descriptions to a wider audience, since movable type had made publishing far cheaper than copying by hand. Fitting a lens turned a dim, blurry pinhole image into a bright, sharp one, and lens grinding was improving anyway through work on telescopes and early microscopes. For the first time, the camera obscura could serve as a window onto the world, a way to see a moving landscape rendered flat on a surface, a view that fascinated educated Europeans.
From room to box
Over the 1600s and 1700s the device shrank. Instead of a room, designers built tents, sedan-chair-sized cabins and finally portable boxes with mirrors that flipped the image upright for tracing. A design published by Johann Zahn in the late 1600s, with a reflex mirror and ground-glass screen, resembles the later single-lens reflex layout. Such boxes were used by amateur artists, surveyors and travelers.
The bridge to photography
The camera obscura gave early photographers the box, the lens and the screen they needed. Thomas Wedgwood in England and Nicephore Niepce in France both tried to put light-sensitive material where the viewing screen had been, and their work led to lasting photographs. The photographic camera is, in structure, a camera obscura with a recording surface.
Public attractions
In the nineteenth century, large camera obscuras became tourist attractions. An example in Edinburgh, which opened in the 1850s on a hill near the castle, projects a live view of the city onto a white table in a darkened room, and similar installations operated in seaside towns and observatories in Britain and elsewhere. Several still operate. They are low-technology attractions that remind visitors how a lens and a mirror can produce a moving image without any need for electric lighting or a screen.
Modern uses
Art. The American photographer Abelardo Morell began in the 1990s to turn hotel rooms and apartments into camera obscuras by blacking out windows and leaving a small hole, then photographing the inverted view of the city across the interior. His images became widely known and show the effect clearly.
Education. Teachers use cardboard-box pinhole viewers to demonstrate how images form and to watch eclipses indirectly. Indirect projection is a safer way to view the sun than looking at it, though instructions should be followed carefully, since looking directly at the sun can injure the eyes.
Pinhole photography. Hobbyists make pinhole cameras from boxes or cans and expose photographic paper or film for seconds to minutes. The images are soft but have a distinctive depth of field, and the practice has a small, dedicated following.
Technology. Engineers still use the same principle in some specialized sensors and imaging systems, though most modern optics rely on lenses. Digital sensors, which are silicon chips, have replaced the screen or paper at the back of the box, but the arrangement is the same.
What is certain and what is not
It is well established that the principle was understood in antiquity and used by artists and scientists in Europe from the Renaissance. It is much less certain which individuals first built a practical device, and claims that famous painters relied heavily on lenses and projections are debated. This article avoids settling those arguments.