Photography
2 of the 7 encyclopedias on this shelf carry an entry for Photography. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
Important: Safety Warning This page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes. This information has been left in for historical purposes but should not be acted upon. the art of producing permanent pictures by means of the chemical action of light on sensitized surfaces. The first to produce permanent pictures by the chemical influence of light was M. Niepce at Chalais-sur-Mer, in 1814, and his idea of the development of a latent image by treatment after exposure lies at the basis of photography. Niepce and Daguerre discovered that they were conducting experiments of a kindred character, and in 1829 entered into partnership. Daguerre, with Niepce's son Isidore, carried on this work in 1839, and invented the process known as the daguerreotype. The introduction of collodion in 1857 was a great step in photography. The collodion process is divided into five stages: (1) The preparation of a clean glass plate by coating with collodion to which bromide of cadmium and either iodide of potassium or iodide of ammonium has been added. (2) The sensitizing of the collodion by immersion in a bath of nitrate of silver, and distilled water. (3) The production of a latent image by exposing the sensitized plate in the camera. (4) The development of latent into visible image by immersing the plate in a solution of sulphate of iron or pyrogallic acid, to either of which some acetic or citric acid is added. (5) Fixing of the permanent image by immersion of the plate in some solvent of those parts of the sensitive surface upon which the light has acted. This solvent for wet plates is cyanide of potassium, but for more modern processes hyposulphite of sodium is employed. On account of the trouble of preparing the wet collodion plates, the dry plates, made by the gelatine-bromide process, have almost universally taken their place. Dry plates made by some form of this gelatinebromide process are manufactured on a large scale. When properly made they are much more sensitive than the collodion plates and will keep good for years, and can be developed months after exposure. The positive prints are made by the action of light, passing through the developed plate, on a sensitized paper, over which the plate is placed. The silver, platinum, and ferro-prussiate papers are the most used. Silver Process. - Suitable paper is coated on one side by a thin layer of albumen, to which chloride of sodium or of ammonium has been added. The old method of dispensing with albumen and using paper which is salted only, is reviving. The paper is sensitized by floating it on a solution of silver nitrate, and drying. After printing, the paper is treated with a solution of chloride of gold, which tones it, producing different shades of color, depending on the length of immersion and strength of solution. After toning, the print is fixed in the same manner as the plate, by a solution of hyposulphite of sodium, which removes the undarkened silver salts. Gelatine or collodion is sometimes used in place of albumen in this silver-printing process. All soluble substances have to be washed from the prints after they have been toned and fixed because otherwise the photographs become ultimately discolored. The papers known as aristotype, argentotype, and celerotype are gelatine emulsions of chloride of silver spread on paper. Platinum Process. An image can be obtained in platinum black if the paper is sensitized with ferric-oxalate with which is mixed a solution of chloro-platinite of potassium. The action of light on this paper reduces the ferric salt to the ferrous state, and when the ferrous salt is in solution the platinous salt is reduced by it. By floating the exposed paper on a solution of neutral potassium oxalate, which is a solvent of the ferrous oxalate, the platinum salt in contact with it is immediately reduced to the metallic state, and an image is thus built up. To fix the prints they are immersed in dilute hydrochloric acid, which dissolves away the ferric oxalate, and the oxalate of lime. Ferroprussiate Process. - The ordinary method of making blue prints. Composite photography, a method of superposing several or many photographs, thus getting a sort of average of the whole and showing the type. If it is a human composite photograph type, then the eyes of each sitter are brought to the same place on the lens, and the exposure for each is very short. The most important advance in photography in recent years has been made in the direction of taking photograph natural phs colors. Many scientists have in worked on the problem and several processes have been developed. The most remarkable of these was perfected in 1907 by Antoine Lumière and his sons August and Louis, of Paris, who succeeded in taking color photographs on a single plate and in an ordinary camera, with exposures of one second and less. Their process consists in the formation of a color screen on a glass plate by placing on it a layer of microscopic grains of transparent potato starch, in three portions colored respectively orange, green, and violet; the plate is then sensitized by coating with a gelatin - bromid emulsion. After the exposure, the plate is developed by a double process that turns it to a positive and the result is a beautiful transparency in the natural colors.
Aiton's Encyclopedia (1910)
fo-tog'ra-fy, the art of taking pictures by means of light. It is hard to say when the effect of light on color became a subject of study. In the eighteenth century Scheele, a Swedish chemist in the University of Upsala, found that the violet rays of the solar spectrum darken silver chloride. In 1839 Daguerre, a Paris scene painter, published a method of taking pictures. His process consisted in coating a silver plate with iodide, then exposing it in a camera. The different degrees of light proceeding from the light and dark places of the object produced corresponding differences on the iodide of the plate. This difference was brought out and fixed by a subsequent bath in vapor mercury, the mercury adhering to the several parts of the plate in proportion to the extent to which it had been affected by light. This sort of picture was named a daguerreotype in honor of the inventor. The first sun-lit picture of a human face was taken by Professor John Draper of the University of New York . In 1840 he took a daguerreotype of his sister Dorothy. It is still in existence in the family of William Herschell of England, to whom it was sent as a scientific curiosity. Daguerreotypes were expensive. They required a long, tedious sitting, and then only one picture could be produced. An account of the various substitutes for silver and iodine and the improvements which enable a photographer to produce an unlimited number of photographs from one plate are too technical for our purposes. A method of instantaneous photography has been developed, so short a time exposure--a mere fraction of a second--that it is practicable to obtain a clear picture of objects in motion, as a moving train or a trotting horse. In 1888 George Eastman, of Rochester, New York, devised a miniature hand camera which he named the kodak. It contains a reel of sensitive paper on which many impressions may be taken to be developed later. The manufacture of kodaks has risen to commercial importance. It still centers at Rochester. Photography has acquired an importance among scientists. Descriptions may err or fail to carry an intended meaning. Sunlight records facts or, at least, appearances. In legal affairs a photograph is accepted as the best of evidence. The astronomer uses the camera. During an eclipse the observer busies himself taking a series of photographs to be studied at leisure. Astronomers are employed busily photographing the heavens as a record of the present position of the stars. A score of telescopic cameras are at this work in various parts of the world. Naturalists are taking photographs of lions in Africa, elephants in their native jungles, and of bird, beast, and fish everywhere. The hunter with camera, instead of rifle, creeps up or lies in wait. If in darkness, he uses a flashlight--a moment of exposure--and he has his picture faithful to life. To obtain a photograph of a bird on her nest the naturalist resorts to the device of setting the camera in position. He then retires to a place of concealment at a distance, and at the right moment exposes by pulling a long cord. Cameras, and indeed, series of cameras, are sent aloft by means of a kite and are operated by a cord to obtain views of the horizon, of fortifications, and bird's-eye views of cities and landscapes. A tiny self-acting camera strapped to the breast of a pigeon has been sent aloft. It has been suggested that pigeons be trained to spy on the movements of armies in the field. Not least among the services of the photograph is its use in education and in art. At a cost of a few cents each it is now possible to bring pictures into the schoolroom and to decorate the home with photographic reproductions that are excellent from an artistic point of view. Although persons are yet living who can remember the interest aroused by the first daguerreotype, the business of manufacturing photographers' supplies has risen in the United States alone to the value of $30,000,000 a year. 2026 Editor's Note: Photography had just gone universal — Kodak's $1 Brownie (1900) put a camera in every hand, and this entry's era is the first the future can see in snapshots. See the Brownie . (Ed: BR 2026-06-19)