Henry Fox Talbot

William Henry Fox Talbot

William Henry Fox Talbot (1800-1877) was a British inventor but also the creator of "The Calotype". His journey into photography began with earlier studies and in depth research about optics. It was by means of his research that he later developed "The Calotype". 

Talbot also used similar elements and compounds for his images. He used silver iodine, which itself is a very sensitive element, and exposed it to light. By doing so, the element decomposed to silver which left iodine as a single element. Since silver oxide is black, Talbot knew that the resulting image would be visible. He then used Potassium Bromide in order to stabilize the silver oxide. 

Talbot proceeded to experiment with salted paper, in which the sensitive element was silver chloride (when salt reacts with silver nitrate). This time when he exposed it to light, he noticed that silver chloride decomposed which left silver as the single element whilst chlorine just evaporated. Talbot then stabilized the silver oxide on the paper with hyposulphite of soda (photographic fixer). He started to notice that during long exposures of direct sunlight, the paper itself would become quite hot in temperature, this in turn allowed Talbot to create a "negative image" on the silver iodine form which positives could be printed out (onto silver chloride paper).

Unlike the Daguerrotype, Talbot's images contained muted tones and his invention also yielded the possibility of multiple copies (through use of negatives).

Below is a great demonstration/process of how a Calotype can be created (as explained above).

The Calotype Process - http://www.youtube.com/watch?v=oD30ajWuHUI

References:

1) Bellis,M, 2013, "History of Photography and the Camera". [online]
Available - http://inventors.about.com/od/pstartinventions/a/stilphotography.htm

[Accessed 23rd October, 2013]

2)Wikipedia.org [online] Available - http://en.wikipedia.org/wiki/Henry_Fox_Talbot

[Accessed 23rd October, 2013]