Appareil photo:Nikon D3200:359.99 € Fnac.com

Appareil photo:Nikon D3200:359.99 € Fnac.com

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Appareil photo:Nikon COOLPIX L840:179 € Auchan.fr

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A camera consists of at least one darkroom, a device whose principles have been known at least since Antiquity. With an opening on one side to let in the light emitted by the scene to be photographed and on the other a sensitive surface to record this light.In the most frequent case, a lens is positioned at the aperture. Most often, it contains a diaphragm making it possible to measure the quantity of light which enters, as well as the depth of field (these two aspects being linked). Some lenses (simple amateur models or catadioptric lenses) use fixed apertures.There are a few devices that don't use a lens: pinhole cameras. Only a tiny aperture allows the formation of a relatively sharp image, which prevents a large amount of light from entering and therefore results in long exposure times. Hence the interest of the lens: bring in much more light (and obtain a sharper image).Most of the time, a shutter that controls the exposure time of the sensitive surface is installed. Some old rooms do without: the operator (the photographer) just removes a plug in front of the lens for the duration of the exposure - but this is especially valid for the long exposures, commonly used in the beginnings of photography, in accordance with the slowness of the emulsions of the time.The sensitive surfaces used come from two main families: film and digital. In the first case, an emulsion of gelatin and silver salts is used lying on a glass plate or film, in the second a sensor (the images are then recorded on an electronic medium separate from the sensor, most often a memory card).

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