Invention

Part 11 - Cameras

In 1839, Alphonse Giroux produced the first camera in France. It had a lens fitted to an outer box and a holder for a ground glass focussing screen on an inner box. The inner box was slid in or out to focus the image before the screen was replaced with a sensitized daguerreotype plate. A copper flap, in front of the lens, served as a shutter. Coincidentally, in 1839, Sir John Herschel produce the first glass negative plate and was credited with proposing the word "photography", in 1839, based on the Greek words meaning "drawing with light".

Soon after the invention of the daguerreotype, in 1834, William Henry Fox Talbot bathed writing paper in a weak solution of sodium chloride (table salt) that he dried before brushing one side with a strong solution of light-sensitive silver nitrate. The coating darkened where it was exposed to light but the negative images required an exposure of more than an hour and would darken if subsequently exposed to more light. In 1839, John Herschel discovered that hyposulfite of soda ("hypo" or sodium thiosulfate), stabilized (fixed) a photographic image. This made prints less sensitive to subsequent exposure.

Herschel gave his discovery to his friend Talbot who was able to print the camera's negative image, using direct sunlight, onto another sheet of salted paper to create a positive image. In 1841 Talbot introduced his Calotype process which used silver iodide instead of silver chloride for the coating and gallic acid and silver nitrate to fix the image. (Talbot's silver halide negative process is the basic technology used by chemical film cameras today. A silver halide is one of the chemical compounds formed with silver and one of the halogens;- bromine, chlorine, iodine and fluorine. They are all light sensitive compounds but silver bromide is the most commonly used).The Calotype process reduced the exposure time to less than two minutes in bright sunlight and the translucent paper negative made it possible to produce many positive prints by simple contact printing, whereas the daguerreotype was an opaque direct positive that could be copied only with a camera. However the prints images were blurred by the paper fibres and were less sharp than daguerreotypes.

In 1852, Talbot, found potassium dichromate made gelatine less soluble when exposed to light. This discovery was later used for the carbon printing process and laser holography.

Talbot also created the photoglyphic process of etching on copper, steel, or zinc, using light to expose chemicals that permitted parts of the metal surface to be removed by acidic or alkaline solutions. This made the reproduction of multiple images much less expensive and this became the basis for photo-graveur printing.

One of the first attempts at colour photography was demonstrated by Edmond Becquerel in 1848, but exposure time took hours or days and image colours were so light-sensitive they would only be very briefly inspected in dim light.

In 1848 Frederick Scott Archer invented the collodion process which substantially reduced exposure time and combined the fine detail of the daguerreotype with the ability to print multiple paper copies like the calotype. This was typically an emulsion of silver bromide that could be used wet, or dried on the plate for later use. After exposure, the emulsion could be fixed (developed) with an alkaline solution made with pyrogallic acid, alcohol, potassium bromide, distilled water and ammonium carbonate.

Developed in the mid 19th century, emulsion plates, or wet plates, were more convenient for portrait photography, because they needed only two or three seconds of exposure time, and were less expensive than daguerreotypes. Because these plates were much more sensitive to light, they had to be developed quickly. Photographers needed to mix chemicals as needed so many of them travelled in wagons that doubled as darkrooms.

During this period cameras were fitted with moveable lenses and light-proof bellows for better focussing.