page_title: Camera obscura
section_title: 1600 to 1650: Name coined, camera obscura telescopy, portable drawing aid in tents and boxes
hierarchical_section_title: Camera obscura / History / 1600 to 1650: Name coined, camera obscura telescopy, portable drawing aid in tents and boxes
caption_attribution_description: English: Illustration of a twelve hole camera obscura from Bettini's Apiaria universae philosophiae mathematicae" (1642)
context_page_description: Camera obscura, also referred to as pinhole image, is the natural optical phenomenon that occurs when an image of a scene at the other side of a screen is projected through a small hole in that screen as a reversed and inverted image on a surface opposite to the opening. The surroundings of the projected image have to be relatively dark for the image to be clear, so many historical camera obscura experiments were performed in dark rooms.
  The term "camera obscura" also refers to constructions or devices that make use of the principle within a box, tent, or room. Camera obscuras with a lens in the opening have been used since the second half of the 16th century and became popular as an aid for drawing and painting. The camera obscura box was developed further into the photographic camera in the first half of the 19th century when camera obscura boxes were used to expose light-sensitive materials to the projected image.
  The camera obscura was used as a means to study eclipses without the risk of damaging the eyes by looking into the sun directly.
context_section_description: The earliest use of the term "camera obscura" is found in the 1604 book Ad Vitellionem Paralipomena by German mathematician, astronomer, and astrologer Johannes Kepler. Kepler discovered the working of the camera obscura by recreating its principle with a book replacing a shining body and sending threads from its edges through a many-cornered aperture in a table onto the floor where the threads recreated the shape of the book. He also realized that images are "painted" inverted and reversed on the retina of the eye and figured that this is somehow corrected by the brain. 
  In 1607, Kepler studied the sun in his camera obscura and noticed a sunspot, but he thought it was Mercury transiting the sun.
  In his 1611 book Dioptrice, Kepler described how the projected image of the camera obscura can be improved and reverted with a lens. It is believed he later used a telescope with three lenses to revert the image in the camera obscura.
  In 1611, Frisian/German astronomers David and Johannes Fabricius (father and son) studied sunspots with a camera obscura, after realizing looking at the sun directly with the telescope could damage their eyes. They are thought to have combined the telescope and the camera obscura into camera obscura telescopy.
  In 1612, Italian mathematician Benedetto Castelli wrote to his mentor, the Italian astronomer, physicist, engineer, philosopher, and mathematician Galileo Galilei about projecting images of the sun through a telescope (invented in 1608) to study the recently discovered sunspots. Galilei wrote about Castelli's technique to the German Jesuit priest, physicist, and astronomer Christoph Scheiner.
  From 1612 to at least 1630, Christoph Scheiner would keep on studying sunspots and constructing new telescopic solar-projection systems. He called these "Heliotropii Telioscopici", later contracted to helioscope. For his helioscope studies, Scheiner built a box around the viewing/projecting end of the telescope, which can be seen as the oldest known version of a box-type camera obscura. Scheiner also made a portable camera obscura.
  In his 1613 book Opticorum Libri Sex Belgian Jesuit mathematician, physicist, and architect François d'Aguilon described how some charlatans cheated people out of their money by claiming they knew necromancy and would raise the specters of the devil from hell to show them to the audience inside a dark room. The image of an assistant with a devil's mask was projected through a lens into the dark room, scaring the uneducated spectators.
  By 1620 Kepler used a portable camera obscura tent with a modified telescope to draw landscapes. It could be turned around to capture the surroundings in parts.
  
  Dutch inventor Cornelis Drebbel is thought to have constructed a box-type camera obscura which corrected the inversion of the projected image. In 1622, he sold one to the Dutch poet, composer, and diplomat Constantijn Huygens who used it to paint and recommended it to his artist friends. Huygens wrote to his parents (translated from French):
  I have at home Drebbel's other instrument, which certainly makes admirable effects in painting from reflection in a dark room; it is not possible for me to reveal the beauty to you in words; all painting is dead by comparison, for here is life itself or something more elevated if one could articulate it. The figure and the contour and the movements come together naturally therein and in a grandly pleasing fashion.
  German Orientalist, mathematician, inventor, poet, and librarian Daniel Schwenter wrote in his 1636 book Deliciae Physico-Mathematicae about an instrument that a man from Pappenheim had shown him, which enabled movement of a lens to project more from a scene through the camera obscura. It consisted of a ball as big as a fist, through which a hole (AB) was made with a lens attached on one side (B). This ball was placed inside two-halves of part of a hollow ball that were then glued together (CD), in which it could be turned around. This device was attached to a wall of the camera obscura (EF). This universal joint mechanism was later called 
caption: Illustration of a twelve-hole camera obscura from Bettini's Apiaria universae philosophiae mathematicae" (1642)
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