In the third century, Aristotle wrote about observing an eclipse by looking through a small hole in a leaf. He wondered why the light coming through the hole had the round shape of the sun and not the shape of the hole; “is it because, just as, when the light shines through an aperture with regular angles, the result is a round figure [. . .]”1 When he asked why light passing through a small square hole looks round, Aristotle observed the phenomenon that lead to the invention of photography.
When light hits an object it refracts off in straight lines. If that light hits a box with a tiny hole in it, the light is so concentrated that it forms an image on the opposite wall of the box. As the light is traveling in straight lines, the image is upside down, but the color and perspective are perfectly preserved.
These boxes are called camera obscura, Latin for dark room. Throughout history they have been used for science, inventing and entertainment. Egyptian scientist Alhazen (965-1040 CE) used camera obscurae in his experiments on light and vision, earning him the title “Father of Modern Optics.” He placed five lanterns outside a dark room with a small hole in it. Five lights were projected onto a wall in the box. By partially blocking the lights outside the box and observing the effect on the images inside the box, he figured out that the straight path of the light caused inversion of the image.2 He was the first to discover that the projection in his dark room was a complete image of everything the pinhole faced.
Many early astronomers used the device to observe eclipses and to study vision. In his Codex Atlanticus Leonardo da Vinci gives a complete description of the camera obscura: “I say that if the front of a building—or any open piazza or field—which is illuminated by the sun has a dwelling opposite to it, and if, in the front which does not face the sun, you make a small round hole, all the illuminated objects will project their images through that hole and be visible inside the dwelling on the opposite wall which may be made white; and there, in fact, they will be upside down, and if you make similar openings in several places in the same wall you will have the same result from
each. Hence the images of the illuminated objects are all everywhere on this wall and all in each minutest part of it. The reason, as we clearly know, is that this hole must admit some light to the said dwelling, and the light admitted by it is derived from one or many luminous bodies. If these bodies are of various colours and shapes the rays forming the images are of various colours and shapes, and so will the representations be on the wall.3”
He goes on to relate this natural phenomenon to human eyesight. After all, the eye uses a small hole in a dark structure to receive light in the form of complete images. da Vinci knew that images penetrating the eye must be upside down. He never did figure out how the images were turned right side up. Inquirers who followed him discovered the effects of lenses and used them to turn camera obscura images right side up.
At first, camera obscurae were large rooms that viewers could walk into to see a moving picture of the landscape around them. Enterprising artists figured out how to make the device portable and how to use lenses to sharpen the image and flip it right side up. Thomas Jefferson owned a camera obscura that used lenses and mirrors to project an upright image. He also had a scioptric ball, a little known optical device that, when fitted to a shuttered window, turns a room into a camera obscura.4 Many painters used these portable tools to help them paint using perfect perspective. Art historians heatedly debate whether painters like Vermeer used camera obscura to achieve remarkably accurate perspective.5
In 1724 German scholar Johann Heinrich Schulze discovered that silver nitrates become darker when exposed to light.6 He was able to make a temporary photographic image. It wasn’t until the early 1800s that Niecephore Niepce used silver chloride to capture a camera obscura image. Unfortunately, his images continued to react with light and were not permanent. Later innovators such as William Henry Talbot and Louis Daguerre were able to stop the exposure, creating the first permanent photographs.
You can turn a room into a camera obscura. If you have dark curtains, or better yet blackout curtains, tape them together at the middle, leaving only a small gap where you want the aperture for your camera. Cut a small hole in a piece of cardboard and tape it over the gap in your curtains. Voila! You should now have a moving image of the view from your window projected on the wall of your room, upside down.
Camera obscuras are still used today in art and entertainment. Aberystwyth, Wales has the largest camera obscura in the world.
1. Forster, E. S. The works of Aristotle. Trans. W. D. Ross. Vol. 7. Oxford: Clarendon Press, 1927. Digital file.
2. Al-Haytham, Ibn. The Optics of Ibn Al Haytham: On Direct Vision. Trans. Sabra. A. I. Books 1-3. London: The Warburg Institute, 1989. Print.
3. Richter, Jaun Paul. The Literary Works of Leonardo da Vinci. Vol. 1. p. 44. London: Sampson Low, Marston, Searle and Rivington, 1883. Print.
4. “Camera Obscura.” Monticello. The Thomas Jefferson Encyclopedia, n.d. Web. 19 Aug. 2013. www.monticello.org/site/research-and-collections/camera-obscura
5. Steadman, Philip. “Vermeer and the Camera Obscura.” BBC, 17 Feb 2011. 19 Aug. 2013. http://www.bbc.co.uk/history/british/empire_seapower/vermeer_camera_01.shtml
6. Boyd, Jane E. “Silver and Sunlight: The Science of Early Photography.” Chemical Heritage Magazine, n.d. 19 Aug. 2013. http://www.chemheritage.org/discover/media/magazine/articles/28-2-silver-and-sunlight.aspx?page=1