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The Science Behind Cameras (Past & Present)

Everyone loves to capture their most memorable moments or most mundane episodes, but what is going on behind a camera, and what really happened before having one?

The first camera, the pinhole camera, invented as early as 300 B.C., is the simplest type of camera, and probably most commonly learned about in science class. It consists of a light proof box with a light-sensitive film at the back end and a miniscule hole at the front end.

 

This camera works because light rays coming from above and below enter the hole, bounce off, and reach the film in an opposite direction.

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As described, the light from the top of the candle goes to the bottom of the film, and vice versa, forming an inverted picture.

 

These light rays react with silver halide crystals, which are usually made from silver bromide (Ag+Br), and a developer agent inside the film. Light photons reacting with the crystals excite and kick out an electron from the bromide ion. Because the bromide ion is highly reactive, the ion binds with neighboring ions to form bromine (Br2). Meanwhile, electrons move around and sticks to an imperfection (crack) in the crystal. Loose silver ions are attracted to the cracks and form a “metallic seed.” Then, the developer agent and water in the film react with the silver and bromine. When the silver melts, it forms a latent image.

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As this diagram shows, light photons extract an electron from the negative bromide ions. Then, the positive silver ions are attracted and react with the developer agent and water to form an oxidized agent, bromic acid, and a latent image.

This is represented in the following equation:unnamed-9

When a latent picture is created, another component of the film, “the fixer” (sodium thiosulfate: Na2+S2O3-2) reacts with the silver halide to desensitise the film and form a negative, as shown in the following equation:

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And this is the end result:

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This is the original depiction of the first photograph, where two houses form a triangular shadow.

 

 

Before the use of traditional film, pinhole cameras usually required hour-long exposures, which made the pinhole camera inefficient.

 

This led to the next big name for photographers: The Daguerreotype Camera.unnamed-6

The daguerreotype, invented in the 19th century, consists of a silver-covered copper plate inside a camera obscura.

 

Before exposure, the copper plate is polished with a buffer solution and sensitized with chlorine compounds fumes. Then, the plate is placed in a box and held with clamps and a leveling stand to optimize the entrance of light. During exposure, the mercury box reacts with the plate to decrease the required exposure time. And after exposure, the picture is fixed with sodium thiosulfate and gold chloride, washed, and colored.

 

And this is the final result:

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Despite using a similar fixing method to a pinhole camera, the Daguerreotype was more complex and led to shorter exposure times of ten seconds to one minute. However, this camera always had to be used in a studio.

 

That is, until the Reisekamera, the first travel camera, came along.unnamed-4

The reisekamera, invented in the early 20th century, is a wooden, squared camera with a removable brass lens (O) on the front and a plate holder, the matte screen, on the back (M), united by non-tampering bellows (B). The camera is sustained by a tripod (S), and directed by a rack and pinion knurl (T).

When taking a picture, the reisekamera follows the wet-collodion mechanism. A solution of potassium iodide (K+I), collodion (nitrocellulose: (C6H7(NO2)3O5)n), and ether (C4H10O) is poured into a glass plate, and the ether evaporates. Then, the plate is sensitized in a bath of silver nitrate (AgNO3), where light sensitive crystals of silver iodide (AgI) form. The plate is then placed inside the matte screen, and the photographers remove the black veil and lens cap, focus it with the rack and pinion knurl, and expose it.

 

The only disadvantage with this camera was that the plate had to be exposed immediately after the chemical reaction, so photographers had to carry the solutions all the time.

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Picture of a photographer using a Reisekamera.

 

This led to the development of the most viable 35mm camera, the Ur Leica, which will be discussed in the second part of this series.

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Sources:

Chowdhury, Rahul. “Evolution of The Camera.” Onextrapixel, 22 Apr. 2015, onextrapixel.com/evolution-of-the-camera/.

 

Alexis. “Film Processing Chemistry, How Does It Work?” Film Photography Blog, www.film-photography-blog.com/film-processing-chemistry-how-does-it-work/.

 

Johnson, Tim. “Chemistry and the Black and White Photographic Process: The Making of a Negative.” Carbon-14 Dating, www.chem.uwec.edu/Chem115_F00/johnstim/Chemandphoto.htm.

 

“The Daguerreotype Process.” The Daguerreotype Process, Sussex PhotoHistory, www.photohistory-sussex.co.uk/dagprocess.htm.

 

“Reisekamera.” Margaret Bourke-White – Camera-Wiki.org – The Free Camera Encyclopedia, 2017, camera-wiki.org/wiki/Reisekamera.

 

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