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Full text of "The origins of modern photography / by George H. Ducker."

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George H. Dueker 

Photography as we know it today Is the work of many 
men. It began as a result of experiments of alchemists and 
early chemists on the action of light on certain chemicals. 
The fact that silver salts blatekened if exposed to light was 
known by 1565, but not until 1727 did anyone try to use this 
property to form images. In that year J.H. Schulze used a 
mixture of silver nitrate and chalk under stencilled letter 
to form an image after exposure to light. This and similar 
experiments led to the experiments of T. Wedgewood with a 
mixture of silver nitrate on the surface of paper and leather 
in 1tS02. It was also suggested at about this time that silver 
chloride was more sensitive than silver nitrate. These 
experiments were only moderately successful because of 
the length of the exposure required to form an image, ?nd 
the fact that there was at this time no knowm means of 
removing the unexposed silver salt so that the Image 
could be made permanent. 

In these early experiments, the silver salt was usually 
exposed directly to the light, or at best, an image was 
formed by blocking off part of the sensitized surface by 
covering it with a stencil of some sort. Photographic 
images were first formed when one of these sensitised 
surfaces was exposed to the light in a camera obscura. 
The invention of the camera obscura is ' usually credited to 
Giovanni Uattista del Porta in 1533) although a number of 
other inventors discussed the fact that such a device 
could probably be built before this time. D.Barbaro in 
1 568 proposed the use of con -ex lenses and a diaphram to 
secure a greater sharpness of images. This use of lenses 
in cameras greatly reduced the required exposure time. 

In his book published in 1 665, J Zahn described a portable 
camera obscura with a lens to secure greater brilliancy of 
image, and side wings to shield it from extraneous light. 
By the beginning of the 1 8 th century, the portable 
camera obscura had become a regular article of commerce, 
although at this time it was not used by photography. 

Toward the end of the 1 8 th century people began 
to request that some way of preserving the images they 
saw through their camera obscura be devised. Up to this 
time, the only simple way of producing pictures was the 
silhouette. This consisted of simply tracing the shadow 
of whatever the subject of the picture happened to be. 
J. ITicephore Mepce first tried photography with silver 
chloride in 1817ยป Unfortunately,' while he could produce 
images, they were not permanent. The first successful 
photographs were taken in 1822. At this time asphaltum 
was used. When it ife exposed to light, it becomes insoluable 
in its usual solvents. This was the first permanent photograph, 
The process was called heliography. The contrast produced 
in these pictures was poor, and the required exposure time was 
very long. 

In 1829 L.J.M. Daguerre discovered that an iodized silver 
plate could be exposed to light fo'r a few seconds, and the 
image thus formed coulsf be developed if the plate were fumed 
with mercury vapor. The image was then fixed with a solution 
of thiosulphate of soda and toned by treatment with gold 

In 1 839 Fox Talbot announced that he had made permanent 
photographs by using silver iodide with an excess of nitrate, 
and fixation with with sodium thlosulphate. This produced a 
negative image, from which a positive could be produced by 
repeating the same process. Talbot's process was the first 
stage in the real line of photography, the inventions of 
Daguerre and hTiepee being bypaths whose chief importance was 
the stimulation they gave to photographic evolution. 

In 1851 Scott Archer published his wet collodion 
proeess. In this process, a clean glass plate was coated 
with iodized colodion, and sensitized by dipping it in a 
bath of silver nitrate. The plate was then exposed wet , 
and developed immediately with a solmtion of pyrogallol and 
acetic acid, and fixed with sodium thlosulphate. The necessity 
for preparing the plated immediately before exposure and 
developing them Immediately after considerably limited 
the practice of photography, although the process produced 
acceptable pictures. This was the process that was used by 
the well known photographer of the Civil War, Ma their Brady . 

In the 1870's, a great deal of experimental work was 
done in an attempt to replace collodion with a gelatine emulsion 
to eliminate the need to expose the plates while they were 
wet. A number of men working on the problem Independently 
finally solved the problem of making dry plates almost 
simultaneously . 

In 188^- George Eastman developed the roll film system of 
photography. Originally paper was used as the hacking material, 
but it was soon replaced with nitrocellulose film. This film 
was applied at once by Thomas -Zdison to making motion 
pictures. The highly inflammable nitrocellulose film was 
later replaced with cellulose acetate, which is still being 
used to- ay. 

With the development of roll film, all of the basic 
elements of photography as we now know it were in exi stance. 
Since this time there has been a constant improvement in the 
materials used, but the basic processes are still the same. 

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