Interchangeable parts

The invention: 

A key idea in the late Industrial Revolution, the
interchangeability of parts made possible mass production of
identical products.


The people behind the invention:

Henry M. Leland (1843-1932), president of Cadillac Motor Car
Company in 1908, known as a master of precision
Frederick Bennett, the British agent for Cadillac Motor Car
Company who convinced the Royal Automobile Club to run
the standardization test at Brooklands, England
Henry Ford (1863-1947), founder of Ford Motor Company who
introduced the moving assembly line into the automobile
industry in 1913

Instant photography

The invention: Popularly known by its Polaroid tradename, a camera capable of producing finished photographs immediately after its film was exposed. The people behind the invention: Edwin Herbert Land (1909-1991), an American physicist and chemist Howard G. Rogers (1915- ), a senior researcher at Polaroid and Land’s collaborator William J. McCune (1915- ), an engineer and head of the Polaroid team Ansel Adams (1902-1984), an American photographer and Land’s technical consultant The Daughter of Invention Because he was a chemist and physicist interested primarily in research relating to light and vision, and to the materials that affect them, it was inevitable that Edwin Herbert Land should be drawn into the field of photography. Land founded the Polaroid Corporation in 1929. During the summer of 1943, while Land and his wife were vacationing in Santa Fe, New Mexico, with their three-yearold daughter, Land stopped to take a picture of the child. After the picture was taken, his daughter asked to see it. When she was told she could not see the picture immediately, she asked how long it would be. Within an hour after his daughter’s question, Land had conceived a preliminary plan for designing the camera, the film, and the physical chemistry of what would become the instant camera. Such a device would, he hoped, produce a picture immediately after exposure. Within six months, Land had solved most of the essential problems of the instant photography system. He and a small group of associates at Polaroid secretly worked on the project. Howard G. Rogers was Land’s collaborator in the laboratory. Land conferred the responsibility for the engineering and mechanical phase of the project on William J. McCune, who led the team that eventually designed the original camera and the machinery that produced both the camera and Land’s new film. The first Polaroid Land camera—the Model 95—produced photographs measuring 8.25 by 10.8 centimeters; there were eight pictures to a roll. Rather than being black-and-white, the original Polaroid prints were sepia-toned (producing a warm, reddish-brown color). The reasons for the sepia coloration were chemical rather than aesthetic; as soon as Land’s researchers could devise a workable formula for sharp black-and-white prints (about ten months after the camera was introduced commercially), they replaced the sepia film. A Sophisticated Chemical Reaction Although the mechanical process involved in the first demonstration camera was relatively simple, this process was merely the means by which a highly sophisticated chemical reaction— the diffusion transfer process—was produced. In the basic diffusion transfer process, when an exposed negative image is developed, the undeveloped portion corresponds to the opposite aspect of the image, the positive. Almost all selfprocessing instant photography materials operate according to three phases—negative development, diffusion transfer, and positive development. These occur simultaneously, so that positive image formation begins instantly. With black-and-white materials, the positive was originally completed in about sixty seconds; with color materials (introduced later), the process took somewhat longer. The basic phenomenon of silver in solution diffusing from one emulsion to another was first observed in the 1850’s, but no practical use of this action was made until 1939. The photographic use of diffusion transfer for producing normal-continuous-tone images was investigated actively from the early 1940’s by Land and his associates. The instant camera using this method was demonstrated in 1947 and marketed in 1948. The fundamentals of photographic diffusion transfer are simplest in a black-and-white peel-apart film. The negative sheet is exposed in the camera in the normal way. It is then pulled out of the camera, or film pack holder, by a paper tab. Next, it passes through a set of rollers, which press it face-to-face with a sheet of receiving material included in the film pack. Simultaneously, the rollers rupture a pod of reagent chemicals that are spread evenly by the rollers between the two layers. The reagent contains a strong alkali and a silver halide solvent, both of which diffuse into the negative emulsion. There the alkali activates the developing agent, which immediately reduces the exposed halides to a negative image. At the same time, the solvent dissolves the unexposed halides. The silver in the dissolved halides forms the positive image. Impact The Polaroid Land camera had a tremendous impact on the photographic industry as well as on the amateur and professional photographer. Ansel Adams, who was known for his monumental, ultrasharp black-and-white panoramas of the American West, suggested to Land ways in which the tonal value of Polaroid film could be enhanced, as well as new applications for Polaroid photographic technology. Soon after it was introduced, Polaroid photography became part of the American way of life and changed the face of amateur photography forever. By the 1950’s, Americans had become accustomed to the world of recorded visual information through films, magazines, and newspapers; they also had become enthusiastic picturetakers as a result of the growing trend for simpler and more convenient cameras. By allowing these photographers not only to record their perceptions but also to see the results almost immediately, Polaroid brought people closer to the creative process.

Infrared photography

The invention: The first application of color to infrared photography, which performs tasks not possible for ordinary photography. The person behind the invention: Sir William Herschel (1738-1822), a pioneering English astronomer Invisible Light Photography developed rapidly in the nineteenth century when it became possible to record the colors and shades of visible light on sensitive materials. Visible light is a form of radiation that consists of electromagnetic waves, which also make up other forms of radiation such as X rays and radio waves. Visible light occupies the range of wavelengths from about 400 nanometers (1 nanometer is 1 billionth of a meter) to about 700 nanometers in the electromagnetic spectrum. Infrared radiation occupies the range fromabout 700 nanometers to about 1,350 nanometers in the electromagnetic spectrum. Infrared rays cannot be seen by the human eye, but they behave in the same way that rays of visible light behave; they can be reflected, diffracted (broken), and refracted (bent). Sir William Herschel, a British astronomer, discovered infrared rays in 1800 by calculating the temperature of the heat that they produced. The term “infrared,” which was probably first used in 1800, was used to indicate rays that had wavelengths that were longer than those on the red end (the high end) of the spectrum of visible light but shorter than those of the microwaves, which appear higher on the electromagnetic spectrum. Infrared film is therefore sensitive to the infrared radiation that the human eye cannot see or record. Dyes that were sensitive to infrared radiation were discovered early in the twentieth century, but they were not widely used until the 1930’s. Because these dyes produced only black-and-white images, their usefulness to artists and researchers was limited. After 1930, however, a tidal wave of infrared photographic applications appeared.The Development of Color-Sensitive Infrared Film In the early 1940’s, military intelligence used infrared viewers for night operations and for gathering information about the enemy. One device that was commonly used for such purposes was called a “snooper scope.” Aerial photography with black-and-white infrared film was used to locate enemy hiding places and equipment. The images that were produced, however, often lacked clear definition. The development in 1942 of the first color-sensitive infrared film, Ektachrome Aero Film, became possible when researchers at the Eastman Kodak Company’s laboratories solved some complex chemical and physical problems that had hampered the development of color infrared film up to that point. Regular color film is sensitive to all visible colors of the spectrum; infrared color film is sensitive to violet, blue, and red light as well as to infrared radiation. Typical color film has three layers of emulsion, which are sensitized to blue, green, and red. Infrared color film, however, has its three emulsion layers sensitized to green, red, and infrared. Infrared wavelengths are recorded as reds of varying densities, depending on the intensity of the infrared radiation. The more infrared radiation there is, the darker the color of the red that is recorded. In infrared photography, a filter is placed over the camera lens to block the unwanted rays of visible light. The filter blocks visible and ultraviolet rays but allows infrared radiation to pass. All three layers of infrared film are sensitive to blue, so a yellow filter is used. All blue radiation is absorbed by this filter. In regular photography, color film consists of three basic layers: the top layer is sensitive to blue light, the middle layer is sensitive to green, and the third layer is sensitive to red. Exposing the film to light causes a latent image to be formed in the silver halide crystals that make up each of the three layers. In infrared photography, color film consists of a top layer that is sensitive to infrared radiation, a middle layer sensitive to green, and a bottom layer sensitive to red. “Reversal processing” produces blue in the infrared-sensitive layer, yellow in the green-sensitive layer, and magenta in the red-sensitive layer. The blue, yellow, and magenta layers of the film produce the “false colors” that accentuate the various levels of infrared radiation shown as red in a color transparency, slide, or print.relationship to the color of light to which the layer is sensitive. If the relationship is not complementary, the resulting colors will be false. This means that objects whose colors appear to be similar to the human eye will not necessarily be recorded as similar colors on infrared film. A red rose with healthy green leaves will appear on infrared color film as being yellow with red leaves, because the chlorophyll contained in the plant leaf reflects infrared radiation and causes the green leaves to be recorded as red. Infrared radiation from about 700 nanometers to about 900 nanometers on the electromagnetic spectrum can be recorded by infrared color film. Above 900 nanometers, infrared radiation exists as heat patterns that must be recorded by nonphotographic means. Impact Infrared photography has proved to be valuable in many of the sciences and the arts. It has been used to create artistic images that are often unexpected visual explosions of everyday views. Because infrared radiation penetrates haze easily, infrared films are often used in mapping areas or determining vegetation types. Many cloud-covered tropical areas would be impossible to map without infrared photography. False-color infrared film can differentiate between healthy and unhealthy plants, so it is widely used to study insect and disease problems in plants. Medical research uses infrared photography to trace blood flow, detect and monitor tumor growth, and to study many other physiological functions that are invisible to the human eye. Some forms of cancer can be detected by infrared analysis before any other tests are able to perceive them. Infrared film is used in criminology to photograph illegal activities in the dark and to study evidence at crime scenes. Powder burns around a bullet hole, which are often invisible to the eye, show clearly on infrared film. In addition, forgeries in documents and works of art can often be seen clearly when photographed on infrared film. Archaeologists have used infrared film to locate ancient sites that are invisible in daylight. Wildlife biologists also document the behavior of animals at night with infrared equipment.