By Rochelle Forrester


All Rights Reserved


Publication Date 2006


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The invention of photography required the understanding of two scientific ideas, one concerning physics and optics, the other involving chemistry. The optical idea was that of the camera obscura. The camera obscura (Latin for dark room) involves light reflected from an object passing through a pinhole in the side of a box or room and an upside down image of the object appearing on the far inside wall of the box or room. This effect is caused because light travels in a straight line and when some of the light rays reflected from an object go through a pinhole they cross and reform as an upside down picture of the object on the far wall of the box. The image is upside down because the light rays cross as the light rays coming from a lower point on the object will go to a high position on the far wall of the box and those coming from a higher point on the object will go to a lower point on the far wall of the box. The camera obscura had been known since classical times and had been used by Arab astronomers since the 9th century to look at the sun, stars and the moon. Roger Bacon in the 13th century and Leonardo da Vinci in the 15th century knew of the camera obscura and in the 16th century a lens was used in place of the pinhole. The image produced on the inside back wall of the box or room was of limited use as it could not be kept or reproduced.

It was to take a series of discoveries in chemistry before camera obscura images could be given permanence and could be reproduced. In the 18th century it was known that some compounds of silver, particularly silver nitrate and silver chloride, blackened on expose to sunlight. In 1802 Thomas Wedgewood and Humphrey Davy took the first photographs by placing leaves on top of a piece of white paper, coated with a silver nitrate solution, in the sunlight. Where the leaves covered the paper the paper remained white, while the rest of the paper blackened. This created the worlds first negative but the photograph could not be fixed and the white areas soon darkened when exposed to light. Wedgewood and Davy also experimented with putting the treated paper in a camera obscura but where unable to find anyway of making the images permanent.

It was a Frenchman Joseph Niepce who in 1827 discovered how to make an image permanent. He used a resin called bitumen of Judea to coat a glass plate and exposed it to an image in a camera obscura. Where the light hit the plate the resin hardened and turned white. The unhardened areas were darkened with iodine vapor to contrast with the white parts. Niepce produced the first permanent negative but his process has the grave limitation of an exposure time of many hours.

It was not until 1839 that a more practical method of producing a photograph with an exposure time of about 30 minutes was invented by Jacques Daguerre. Daguerre used a silver plate coated with a layer of silver iodine, a compound very sensitive to light. When the plate was exposed in the camera the picture appeared and was developed using mercury vapor and the image was fixed with sodium hyposulfite. The process soon became known as Daguerreotype.

A further photographic process was independently invented by William Talbot in 1839 and was improved in 1841. Talbot treated paper with silver nitrate, potassium iodine and gallo-nitrate of silver and exposed it to a camera obscura. He obtained a negative which he then lay in sunlight on top of paper treated with the same chemicals to produce a positive. Talbot found he could produce as many positives as he liked from a single negative and it was this advantage that resulted in his process, soon to be called Talbotype, being preferred over Daguerreotype, which produced only one photo for each exposure.

The wet collodian process was developed in 1851 by Frederich Archer and was soon to supersede both the Daguerrotype and Talbotype processes. The collodian process involved using a glass plate for the negative image, rather than paper. Liquid chemicals such as nitrocellulose and silver bromide were poured on the glass plate which was placed in the camera and exposed while the glass plate was still wet. The process was not very user friendly with photographers often getting the chemicals over their hands, arms and clothes. The process also required that photographers carry substantial equipment around in order to do their photography. However exposure times were down to about ten seconds depending on the size of the plate and intensity of the light.

Experiments began with the use of dry plates from about 1853 as dry plates did not require immediate development and reduced the equipment photographers had to carry around. Early dry plates however had very long exposure times so that they were seldom used until after 1871 when Richard Maddox invented the gelatino-bromide dry plate which soon had an exposure time of one second. Between 1874-80 a cheap and fast way of making multiple prints from a single negative was invented. The process involved using a gelantine coated paper sensitized with silver bromide, a compound very sensitive to light. The process allowed prints to be made in the dark room without having to expose the print paper to sunlight.

Popular use of photography expanded enormously when in 1888 George Eastman introduced the Kodak camera. The camera used a flexible roll film made of paper coated with a light sensitive emulsion. A year later celluloid film was introduced which made the processing of the film cheaper and easier.

Color photography was experimented with in the late 19th century but the first practical system of color photography was introduced by Louis and Auguste Lumiere in 1907. Their autochrome process involved photographic plates on glass coated with red, green and blue granules that acted as color filters allowing some light rays through and reflecting others. Other color photographic processes were soon introduced and in the 1920ís and 30ís smaller hand held cameras were introduced. In the late 1960ís electronics was introduced into photography in the form of light sensitive photocells which determine the exposure time for photographs.

Photography has had a major effect on society in a number of areas. In science photographs were taken through microscopes and telescopes to provide permanent and accurate pictures of everything from magnified insects to stars and galaxies. Photographs could show movement that could not be seen with normal vision. Photographs were taken of galloping horses to show that at times they had all four hoofs off the ground and of birds in flight.

Social reform was effected by photographs when photographs of sub-standard living conditions and of child labor hastened efforts to improve housing and to ban child labor. Photographs of war lead to greater understanding of the horrors of war which could never be shown by paintings which tended to glorify war. Photographs of the Vietnam War are often credited with undermining American public support for the war. Magazines began using photographs both in advertising products and in news stories from around the mid 19th century. Photography also became an art form taking over the role of portrait painter and producing many other pictures previously produced by artists. This encouraged art to move towards more abstract images which could not be produced by photography until quite recently. Popular photography became widespread with the introduction of the Kodak camera. Pictures taken during holidays or of friends and family began to fill family photo albums.

Photography was only possible due to certain properties of light and of chemical compounds, such as silver nitrate and silver chloride. Light when passing through a pinhole into a dark room or box will produce an image of the scene outside the box or room on the far inside wall of the box or room. If this property of light did not exist their would have been no photography. The light sensitive nature of certain silver compounds was also vital to photography in order to allow the image provided by the camera obscura to be fixed and made permanent. If those light sensitive chemicals did not exist photography could not exist. The invention of photography could only take place after the discovery of the camera obscura effect and after the discovery of the light sensitive properties of the silver compounds. The camera obscura effect had been known since classical times while the light sensitive properties of the silver compounds became known after a series of experiments by European scientists such as Georg Fabricius, Angelo Sala, Wilhelm Homberg, Johann Schultze and Carl Scheele in the 16th, 17th and 18th centuries. Their discoveries were known to Wedgewood and Davy when they created the first photograph and to Niepce, Daguerre and Talbot when they discovered ways of fixing and making photographs permanent. Both the process of creating the photograph and fixing it were dependent on prior discoveries in chemistry made in the few hundred years before photography was invented in the 19th century. The existence of the camera obscura effect and of light sensitive chemicals which enabled an image to be fixed to produce photographs shows how the structure of the universe has a major effect on human social and cultural history.

The process by which photography developed in the 19th century followed a logical pattern with the easier discoveries being made before the more difficulty discoveries. How to create the photographs was discovered, as it had to be, before how to fix them was discovered. Black and white photography was invented before color photography as color photography involves additional complications than there are with black and white photography. Throughout the 19th century exposure times for photography fell as new and improved techniques were developed. The whole process was improved until amateur photography became possible towards the end of the 19th century.


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