Friday, 10 December 2010
When photographic material is exposed to light it begins to darken. The more light the material receives, the darker it becomes.
In room lighting, this is not very noticeable at first but after a few minutes the darkening can be seen. The brighter the light and hence the name Sun picture, the quicker the darkening of the photographic material occurs. The more generic title given to Sun pictures is Photogram. Photograms are basically made by keeping some parts of the material covered while exposing the rest to sunlight. The easiest material to use is photographic paper. Exploring the effect of light on photographic materials can become an art form by itself. The number of experiments and the list of items that can be placed on the material are just about limitless.
A Photogram is a generally a contact print. It is made by placing something opaque or translucent on light sensitive material and then exposing it to light. This blocks out part of the light, and makes a pattern or picture on the light sensitive material when it is exposed to light. Unfortunately with continued exposure to light the picture can disappear as the rest of the light sensitive emulsion changes colour. Once the subject is removed to look at the picture, the white parts will gradually darken, so the picture begins to fade away. To make the image permanent it is immersed in a dish of fixer for a few minutes and then washed in clean water. Paper that has been darkened by the sun changes its colour in the fixer and again when it dries.
INSTRUCTIONS ON HOW TO MAKE PHOTOGRAMS found here: http://www.ephotozine.com/article/Making-a-photogram--traditional-darkroom-ideas-4688
Camera-less photographs, which are made by blocking light or casting shadows on light sensitive paper or chemically manipulating its surface, have been around since the early 19th century.
The first documented photographs made without cameras were produced in 1802 by Thomas Wedgwood and Humphry Davy but the process was later perfected in 1835 by the inventor of the photographic negative and photographs on paper, William Henry Fox Talbot.
Sometime in the 1790s, Wedgwood devised a repeatable method of chemically staining an object's silhouette to paper by coating the paper with silver nitrate and exposing the paper, with the object on top, to natural light, then preserving it in a dark room. The establishment of this repeatable process was, essentially, the birth of photography as we know it today. Wedgwood thus became one of the earliest experimenters in photography - and certainly the earliest who deserves the title of "photographer", conceiving of prints as pictures. It should be noted, however, that new discoveries in the prehistory of photography are being made by historians almost every year.
William Henry Fox Talbot
Credited as one of the inventors of photography, William Henry Fox Talbot began experimenting with light-sensitive chemistry in 1834. He kept in close contact with astronomer and photographer Sir John Herschel while developing the medium. In 1839, Talbot announced his invention of photogenic drawing two weeks after the daguerreotype process was unveiled in France. Talbot’s calotype process was introduced in 1840, a process that shortened exposure time and allowed for multiple prints to be made from one negative. Talbot published “The Pencil of Nature” from 1844 to 1846, the first commercially published book to contain photographs as illustrations.
Sir Humphrey Davy was an English chemist who worked closely with Thomas Wedgwood. Their work was very nearly a breakthrough, for they had made what one can best describe as photograms but unfortunately they were unable to find a method of fixing them.
In the report to the Royal Society, June 1802, Davy wrote: "The copy of a painting, or the profile, immediately after being taken, must be kept in an obscure place. It may indeed be examined in the shade, but, in this case, the exposure should be only for a few minutes; by the light of candles or lamps, as commonly employed, it is not sensibly affected."