The word 'photography', first used in 1839, is derived from the Greek words for 'light' and 'writing'. The word 'camera' comes from the Latin word for vault or room, the camera we use on our holidays is literally a 'closed vault' into which no light can enter. However, photography as we know it was only possible after the discovery of light-sensitive chemicals to record and develop the image.
Around 350 BC, Aristotle, viewing a partial eclipse of the sun, noticed that the small holes between overlapping tree leaves projected images of crescents onto the ground.
By the mid-16th century, artists regularly exploited this phenomenon in the camera obscura (Latin for ‘dark room’), which they used as an aid to making sketches before painting. In a camera obscura, light passing through a small hole in one wall of a darkened room projects an inverted image of a well-lit scene onto a screen inside the room.
In 1550, a mathematician named Girolamo Cardano suggested using a lens to brighten and sharpen the image obtained in this way. Other modifications followed and by the 18th century the camera obscura had been miniaturised to the size of a portable box. The prototype camera had arrived! There was, however, one thing missing. . . .
It wasn’t until the early 19th century, with the discovery and development of light-sensitive chemicals, that it became possible to record images in a more permanent form, thus avoiding the necessity of drawing.
Chemists had known for some time that silver salts darkened on exposure to light, due to the formation of metallic silver. Sir Humphrey Davy was one of many who attempted to use silver salts to create a lasting image on paper. The images he obtained took a long time to form and darkened all over when further exposed to light.
It wasn’t until 1826 that the first permanent image was produced on pewter-bitumen plates by Joseph Niépce. He used a camera obscura fitted with a lens, and an eight-hour exposure! The photograph, which he called a ‘heliograph’, still exists today.
Before he died, Niépce had started collaborating with fellow Frenchman Louis Daguerre, who, in 1839, developed a different method for producing a permanent image that required much shorter exposure times. He exposed a silver-coated copper plate to iodine vapour, producing a thin layer of silver iodide. This turned dark (formed silver metal) on exposure to light, thus producing a weak negative image – effectively the same process used by the Rough Science team. He then accidentally discovered that exposure to mercury vapour for as little as 15 minutes ‘developed’ the image further. He later found how to ‘fix’ his developed image so that the silver no longer reacted to light and the high-quality positive image became permanent.
The ‘Daguerreotype’ was an immediate success although the process was expensive. Also in 1839, Henry Fox Talbot invented a rival process to that of Daguerre, using paper coated with silver iodide. This so-called ‘Calotype’ method produced negative images which could be made permanent.
Fox Talbot’s process had one significant advantage over the Daguerreotype, each of which was a unique positive image that couldn’t be copied. By contrast, Fox Talbot’s Calotypes were paper negatives, from which many positive copies could be printed.
In 1851, the Englishman, Frederick Scott Archer came up with yet another method that was better still. He suspended the light-sensitive silver salts in a synthetic resin called collodion. This was then coated onto a glass plate. Fifteen times faster than the Daguerreotype, it was a resounding success because of the greater speed and quality of reproduction.
All the great photographers of the day adopted this method, despite the fact that collodion (gun cotton dissolved in ether), was an explosive!
Photographic records of the late 19th century, which up until then had comprised mainly buildings and landscapes, became much richer and more complete. Also, with much shorter exposure times, portrait photography was now possible for the first time and animate objects could be captured on film.
The main disadvantage of the process was that the photograph had to be developed while the image plate was still wet. However, in the late 1880s, George Eastman produced a thin, transparent, flexible strip of celluloid coated with light-sensitive emulsion. Unlike wet plates, the image didn’t need developing before the emulsion dried, and amateur photographers could buy ready-made plates instead of having to make their own.
Eastman Dry Plate Company
In 1879, Eastman devised a machine to mass produce his invention and founded the Eastman Dry Plate Company. His patented photographic film reduced the size of cameras, which were returned to the factory for the film to be developed and the camera reloaded.
As Eastman’s famous advertisement boasted, “You press the button, we do the rest”. After registering the Kodak trademark in 1888, he launched the Brownie, a simple box camera costing $1, making photography accessible to all. The next big challenge was to develop colour film.
In the past 20 years we’ve seen yet another revolution, with digital photography, in which pictures are stored in computer memory and reproduced electronically. Chemistry has been superseded by electronics, which now allow images to be manipulated using image-processing computer software. We’ve come a long way since Niépce’s day.
THE SCIENCE OF COLOUR PHOTOGRAPHY
Colour films consist of three layers of light-sensitive compounds. Effectively, the top layer is sensitive to blue light, the next layer sensitive to green light, and the bottom layer sensitive to red light.
Thus, each layer forms a different negative image, depending on the colour of the light hitting that particular part of the film. Each of these images can then be converted to a positive image (in blue, green and red, respectively) that, when added together, reproduces the true colour of the object photographed.
In 1891, Gabriel Lippmann obtained the first direct colour picture by a process that won him the 1908 Nobel Prize for Physics. Unfortunately, the coloured images could only be seen at a certain angle and copies couldn't be made.
In 1903, the Lumiere brothers introduced their 'Autochrome' process which remained popular until 1935. The technique produced masterpieces, very similar to paintings in their textures and rich colours.
This process was superseded in 1935 by 'Kodachrome', invented by two American musicians, Mannes and Godowzky. The German Company Agfa followed it up in 1936 with 'Agfacolor', a process that was immediately used in Hitler's propaganda campaign. There has been sustained competition to dominate the colour-film market, each company developing the technique one step further, leading to the superb quality colour films we use today.
Book 4 of ST240, Our Chemical Environment, The Open University, 1995 ISBN 0 7492 5144 1.
Jeffrey I., Timeframes: The story of photography, Amphoto Art (USA), 1998 ISBN 0 8174 6015 2.
Langford M., Story of Photography: From its beginnings to the present day, 2nd edn., Oxford Focal, 1997 ISBN 0 2405 1483 1.
Lemagny J-C. and Rouille A. (eds.), A History of Photography: Social and cultural perspectives, translated by Janet Lloyd, Cambridge University Press, 1987 – ASIN 0 5213 4407 7, out of print.
Singer C. et al. (eds.), ‘The photographic arts: photography’, Chapter 30 (Part 1), A History of Technology, vol. V, Oxford University Press, 1958.
Here are some books and articles that you may want to try and get hold of:
Barrow J. D., The Artful Universe, Oxford University Press, 1995 ISBN 0 1985 3996 7.
A quite remarkable book that will change the way you view the world. Extremely accessible.
Burton et al., Chemical Storylines, G. Heinemann Educational Publishers, 1994 ISBN 0 435 63106 3.
Part of the Salters Advanced Chemistry course, which explores the frontiers of research and the applications of contemporary chemistry. For A level and other science courses aimed at 16 to 19-year olds.
Fraser A. and Gilchrist I., Starting Science (Book 1), Oxford University Press, 1998 ISBN 0 19 914235 1.
Part of an integrated science course for the National Curriculum Key Stage 3 and Scottish Environmental Studies (science) for S1 and S2.
Northedge A. et al., The Sciences Good Study Guide, The Open University, 1997 ISBN 0 7492 3411 3.
Indispensable for students of science, technology, mathematics and engineering. Packed with practical exercises and activities, all aimed at making studying more enjoyable and rewarding. Lots of hints and tips for those returning to study.
Selinger B., Chemistry in the Marketplace, 5th edn., Harcourt Brace, 1998 ISBN 0 7295 3300 X.
An excellent and informative reference source for all kinds of real-life applications of chemistry. Explores the world of chemistry that surrounds us in our daily lives, explained in terms that everyone can understand. ‘Makes chemistry come alive.’
PS547 Chemistry for Science Teachers course materials, The Open University, 1992
A course designed for use by science teachers from a wide variety of backgrounds, with varying experience of teaching science. A familiarity with some basic science (perhaps physics or biology) is assumed, but little understanding of chemistry is required. The mathematical understanding needed for the course is not great.