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History of the Camera Obscura

 

Optical games have always attracted human beings; lenses, lights, shadows …or more precisely, stimuli which help us to perceive reality from a different point of view.

At the end of the Xth century, we already knew about the camera obscura with Alhazen, (965-1038) who described this phenomenon perfectly: he Historia2used the principle of the camera obscura in order to explain how the image gets formed in the eye.

Before, we also had had evidence of the observation of the phenomenons and the effects of the sunlight produced by the Camera Obscura: since the fifth century in a few texts written by chinese philosophers and, in the fourth century in a referente by Aristotle. However, until Alhazen its relation with the formation of the optical image was not introduced.

During the Middle Age, Roger Bacon continued with Alhazen´s works about the refraction and the reflection of the light, but he didn´t succeed in describing a camera obscura even if he knew about its existente.

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During the Renaissance, Leonardo da Vinci gave an impulse to the development of the camera obscura, using it to study in depth how the vision works, how the Light reacts and the laws of geometric perspective: he related all that to the painting techniques. Leonardo da Vinci was very curious and also fascinated by the phenomenon of the camera obscura which is able to make the sun´s rays pass through a small hole wihout mixing up one with another.

The first written reference to the lenses was made by the mathematician Girolamo Cardano (1501-1576) in 1550, but the scientist Giovanni Della Porta was the one who, eight years later, spread this piece of news around the World.

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In the XVIIth century, Robert Hooke (1653-1703) built cameras oscuras, and tried to reproduce the curved shape of the retina, wiith concave screens of projection situated at the bottom of the camera. The intention was to demostrate the mechanism of the human vision.

He also built different types of portable cameras obscuras, used to make illustrations in the travel guides and for topography

In 1685, Zahn published a book in which he collected this kind of cameras obcuras and explained the model which didn´t change until the invention of photography in the XIXth century.

With that model, an inclined mirror reflects the image projecting it on to a paper situated on the glass situated on the top of the camera. The lens was situaded at the end of a tube which slides into another one in order to focus at different distances.

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In the XVIIth century is concerned, we can find several studies which try to involve the use of the camera obscura in the dutch painting, due to its “appearance of reality”.

Although we don´t have forceful evidence to prove the systematic use of the camera obscura by the famous artists, we can perfectly give proof of its use by travellers and drawers all the XVIIth and the XIXth centuries long till the time of the photography.

The XVIIIth century, is the most important in the history of the camera obscura, therefore the best techniques and the construction of new models such as its wide dissemination through a large number of publications.

In the XIXth century, the importance of the landscape´s “genre” had repercussions on the academical teaching system, in which the use of the camerahistoria8 obscura succeeded in being a fundamental subject in the fine arts career.

What´s more, it is known that the creador of the photography, Nicéphore Niepce (1765-1833) had bought in 1826 a canera obscura with a lense of meniscos to the engenieers Chevalier´s Optician´s shop in Paris.

Niepce was the first to suceed in “fixing” an image. It happened in 1827 when he suceded in fixing a permanent image of the courtyard of his house. To realise that photography he used a sheet made of pewter and covered with asphalt : he exposed the sheet to the sunlight, so as the image became invisible. Depending on how much sunlight was received , the parts of the varnish exposed to the Light became soluble or insoluble.

In the association “Niepce Daguerre”, an improvement of the camera obscura was reached, adding fixing elements of the image ion to the screen. We also have five cameras obscuras made of walnut in which were put a glass diaphragm, bellows and a system of scales.

 

Gras en inglés

 

Function and description

 

The Camera Obscura projects an image on a white concave horizontal screen, like on a table, which is situated in the centre of completely darkened, black painted room.

The projected images are coloured and luminescent and they reflect everything that happens at this very moment outside the tower (moving images in real time).

Thanks to the large focal distance of the lenses the result is a magnificent optical effect which means that even objects which are far away seem to be near.

To focus the different distances the screen moves up and down, which allows the screen to focus, just like in a camera. The images in the Camera Obscura can be moved forwards and backwards to visualize the different parts of the landscape. Above one can see the horizon at a certain distance, and below, examine details.

The Camera Obscura of Tavira Tower has a plane astronomic object which is produced with a degree/level/grade from 4” (10,16 cm) to 12” (30,48 cm) of diameter and with focal radiuses which are designed for each building in particular.