History

In 1727 J. H. Schulze observed that a mixture of silver nitrate and chalk darkened on exposure to light, this was the beginning of the journey towards modern photography. Nicéiphore Niépce, a French physicist in 1824 then used glass plates coated with silver salts in bitumen to form permanent images. However there still was no method to prevent the continued reaction of light with silver treated photo paper and thus the darkening of photographs that occurred over time. The next development in the process happened purely by accident and provided light-fast images. Louis J M Daguerre, Niepce's partner, found that mercury vapour would develop an image on a copper sheet covered in a surface layer of silver iodide. By washing the plate with hot concentrated sodium hyposulphite (Na₂S₂O₃) the image obtained could be made permanent. In future Sodium Thiosulfate would replace the hot concentrated salt as the solution used to wash off the unexposed silver salts.

In 1841, William Henry Fox Talbot, an Englishman, introduced the calotype process. The process involved coating silver iodide onto a paper, sensitising it to light. On exposure of the light sensitive paper it was then put into a solution of gallic acid, producing a negative. If the paper base that was used was semitransparent, the negative could be placed over another piece of light sensitised paper which created a positive when exposed and developed. Contact printing is the modern equivalent to this process.

Originally egg white was used as a binder to hold the silver salts on the glass. The images were easily damaged, but sharp relative to the Talbot images. This problem was rectified by 1871 by Dr. R. L. Maddox who introduced the concept of gelatin dispersions of silver salts on glass plates. The Kodak system was introduced by George Eastman in 1887. This involves a silver-in-gelatin dispersion coated onto a cellulose nitrate base and loaded into a camera. This new camera was capable of taking 100 pictures and after exposure both camera and film had to be returned to Rochester, New York, for processing.

In 1889 the first flexible films were made, of cellulose nitrate. A film that is nitrate based will deteriorate over time and is highly flammable. In history nitrate film was important because it meant that roll films could be developed.

The more flexible, stable and fireproof triacetate film appeared and was used up until the 1970's. In the 60's polyester polymers were used for gelatin base films and are still used because the plastic film base is not a fire hazard and is more stable than cellulose.

In the past 10 years, film has improved in its contrast and grainy quality. T-grain emulsions have been developed where the light sensitive halide grains are T-shaped, producing a much finer grain pattern. Films like this produce much sharper images by offering greater detail and higher resolution.

It took Joseph Nicéiphore Niépce eight hours to obtain the first fixed image. Nowadays photography is no longer a field of specialists but has evolved into an activity undertaken by the skilled and unskilled alike producing basically the same results.

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