History of Photography – Notes # 2



History of Photography – Notes # 2

The Calotype

Invented by the British scientist William Henry Fox Talbot. His earliest preserved image is a small paper negative produced in August of 1835.

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Negative Positive

Photogram- Silhouette image

Photograph- developed paper negative in contact with another sheet of sensitized paper and exposed both to light sensitive paper, a procedure know as contact printing.

The Process

A sheet of paper was soaked in a weak solution of salt and water and dried. The "salted paper" was then soaked in a silver nitrate solution. The silver nitrate reacted with the sodium chloride to form silver chloride, a light sensitive silver compound. Initially Talbot created photogram’s using objects in contact with the light sensitive paper. In 1835 he created images using a camera obscura. To fix his prints, Talbot used a strong salt solution with potassium iodide which reduced the sensitivity but did not completely fix his images.

Talbot also found that smaller camera obscuras (smaller focal length) and lenses with relatively large diameters created camera obscura images faster than his larger cameras designed for drawing. Typical exposures were about an hour in length, even with his smaller cameras. Talbot also understood the possibility of creating a reversed image or positive from his paper negatives, an idea that would become important to the future significance of his process.

Claim of Priority

Talbot showed examples of his early camera obscura images to a meeting of the Royal Institution of London on January 25th, 1839 and he published his 1st book of photographs called "Pencil of Nature"

In addition to solving the long challenge of a fixing agent for the camera obscura image, Herschel also is credited with proposing the word "photography" to replace Talbot's "photogenic drawing" and the terms "negative" and "positive" instead of "reversed copy" and "re-reversed copy."

From 1841-1850 2 types of primary processes:

 

1.  Calotype-reproductions

2. Daguerreotype- image was clear, detailed and dimensional.

 

At the beginning photography was mainly used for portraiture.

 

1850

Photographers began to use heavy thick glass plates and using new chemical processes.

 

-wet collodian-shorten exposure time, was clear in detail, and used cottons with acids for chemicals to work faster.

 

At this time you could print onto paper.

 

There was a new type of paper in 1850 which was called: 

 

Albumen prints- the process was made by separating egg whites from egg yolk, then coating paper.  This would close up the pores of the paper.

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Albumen Print

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Processing albumen paper

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Drying rack

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