- Pick three events in the timeline from this week’s lesson History of photography: An Introduction , and find photographs of the event on the Internet or in the library and write a paragraph explaining the event in more detail. Include your photographs in the description.
The pinhole camera or camera obscura
The Process of negatives and positives
This is the story of a curious man named Henry Fox Talbot and a forgotten process called the calotype.
Henry was a polymath, he was interested in everything from mathematics, chemistry, astronomy and botany, to philosophy, philology and art history. He always carried around a list of books to read, mathematical problems and observations of experiments. In 1833 his frustration because of his lack of drawing skills, pushed him into start thinking about capturing images into paper. So he started experimenting with paper made sensible to light by coating it with silver salts. This led him to the discovery of something he named “photogenic drawings”, that were negative silhouettes of objects made by direct printing, however the paper wasn’t sensitive enough and it didn’t work well inside a camera obscura.
So, in the summer of 1835 he improved his process dramatically by reducing the size of the camera and attaching large microscope or telescope lenses to shorten the exposure time.
He started placing these cameras all around his house, until he finally achieved his goal and the first negative image was created! This images portrayed reality in a totally different and interesting way. He called this process the “calotype” which means a beautiful picture in Greek.
Talbot spent the rest of his life improving his camera; he started using silver iodide instead of silver chloride to coat his photosensitive paper, and gallic acid and silver nitrate as a developing agent. This resulted in an extremely reduced exposure time of a minute or two for subjects in bright sunlight, and the translucent calotype negative made it possible to produce as many positive prints as desired by simple contact printing. Even thought he had managed to make positive images he still had trouble fixing them to the paper with just a solution of salt. Following a suggestion from a friend he started using hyposulfite of soda to fix the image, which is still used today as a fixer for black and white photography. This improved the process, but despite the effort the pictures taken with the calotype still weren’t as perfect as the guerrotype. Either way, his system was the one that provided the basis for all substantive developments in photography!
Dry plate negatives and hand-held cameras
Even thought a lot of technology around photography had been developed in the 19th century, photographers still needed to prepare, expose, and develop their photographic plates within 10-15 minutes, this implied that they either had access to a studio or that they were able to bring along with them all the materials needed to produce a photography( even dark rooms! ). After this technology started to become old, people started asking questions to make the process easier and faster. So they started experimenting with additives to keep the collodion from completely drying out so that photographers would have more than 10-15 minutes to develop their images.
In 1854, George Salbot developed the honey process with honey diluted in distilled water, where the sugar in the solution kept the collodion moist. After this year people kept experimenting with this sugar concept , using everything from sweet wort, glycerin, to raspberry vinegar and finally the Oxymel process. This process used oxymel, which is a medical tonic of honey and vinegar, as an additive to the collodion plates. This process succeeded in maintaining the photosensitivity for month but resulted in decreased light sensitivity, so the spared time would cost you the quality of the pictures. They kept working on this and several other methods to solve this problem throughout the years.
But it wasn’t before 1871 that a much more successful process was introduced. In this process the sensitizing chemicals could be coated on a glass plate with a gelatin emulsion. This gelatin emulsion consisted of a mixture of gelatin, nitric acid, hydrochloric acid, cadmium bromide, and silver nitrate, coated on a glass plate and allowed to dry. This new dry plate had a long storage life and was 60 times more light-sensitive than collodion plates. This meant that pictures didn’t have to be developed right away and that they had a much better quality now. People continued to develop this idea and in 1879 the technology had improve so it was now practical to manufacture photographic plates for broad consumption. Since photography plates could now be sent to be developed by technicians rather than doing it your self, it became a lot easier and less time-consuming to take pictures, something that increased the amateur participation. It was also a lot easier to take pictures now without the need of a tripod since the light sensitivity had improved a lot.
Here are the sources I have used