The camera obscura
Exclude as much daylight from a room as possible, allowing a single ray to enter through a small opening no larger than a pencil in diameter. Hold a sheet of white paper at a distance of almost 20 cm from the opening and you will see the image of what is taking place outside appear: it will be an upside-down and confused, but recognisable, image. This device for the construction of a stereoscope was described for the first time by Arisottele, in the fourth century BC. It later became the camera obscura, a definition born in Italy. This was the first instrument of the first photographers.
Always, since the Stone Age, men, who lived in caves or in small stone buildings that acted as natural darkrooms, have observed and recorded those subjects that inspired them: the outline sketched on the part of the rock by the rays of the sun, showed them with what force and with what accuracy an object could be transferred onto a flat surface. Undoubtedly they had noticed that some silhouettes persisted when exposed to bright sunlight, for example, in the case of the shadow of a leaf imprinted on the peel of an apple.
The first practical application of the camera obscura
The first big step in the history of photography was finding a practical application of the camera obscura: in the 16th century it became a study tool for painters. Look, Canaletto, Leonardo da Vinci used them among the first, or at least they are the first of which we have certain documentation.
The portable darkroom described by Kircher
In the 50 years that followed, the invention of the optical lens and the diaphragm perfected the original model of the camera obscura. Girolamo Cardano discovered the lens: a biconvex lens, whose name derives from "lentil" due to the similarity of its shape. Daniele Barbaro discovered the diaphragm around 1530.
The portable camera obscura became a common instrument: it consisted of a lens, a diaphragm and a sheet of paper on which the image was imprinted.
The journey towards the first portable SLR
Over time it spread throughout Europe. Althanius Kircher illustrates an example found around traveling in Europe: a small hut light enough to be transported by two men which the artist could enter through a trap door cut into the floor.
dark room
Obviously practicality was essential, and the best minds in Europe committed themselves to reducing its size as much as possible. Kaspar Schott built a box camera in which there were two objectives and a system for adjusting the focus with the adoption of two cameras, one of which, the internal one, could slide into the external body. In England Robert Boyle created a box-shaped camera, whose rear wall was made up of a translucent sheet of greaseproof paper on which the image was released. The same principle was adopted in Germany, in 1676, by a mathematics professor who added a small mirror which, inclined at 45 degrees with respect to the lens, reflected the image, straightening it. Sturm, this is his name, had created the first portable reflex, which a century later, a monk from Wurzburg, replaced the sheet of oiled paper with opaque glass and adopted a telescope lens made up of two elements (one concave and one convex ), of different focal length which gave a magnified image.
Physics had given what it could to the development of the camera: it was necessary for chemistry to intervene.
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