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Chemistry Project

Application of Photography

Hima Angara

on 28 February 2015

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Transcript of Chemistry Project

History of Chemistry in Photography
The first "camera" was the Camera Obscura, which was basically a very dark room with a hole on the side. On a bright day, the image of whatever is outside will be reflected onto the walls upside down.
The beginning of photography can be attributed to the images produced by Johann Heinrich Schulze. After conducting numerous experiments with silver salts (calcium carbonate, CaCO3, dipped in silver nitrate, AgNO3), Schulze found that the substance could be used to create photographs as the substance turned darker when exposed to light.
The first permanent photograph was taken by Nicephore Niépce in 1827 by exposing the silver salts to the sun for a little over 8 hours.
Niépce's partner, Louis Jacques Mande Daguerre, created a process, called the Daguerreotype that cut exposure time to well under a half an hour. Further improvements saw exposure time to be reduced to under 30 seconds.
Daguerreotype images quickly became very popular in the United States and around the world.
A look at the process of producing daguerreotype images and its impact on society
(credit: J. Paul Getty Museum)
Chemicals Involved:
Copper (Cu)
Silver (Ag)
Calcium Carbonate (CaCO3)
Alcohol (C2H6O)
Iodine (I)
Ferric Oxide (Fe2O3)
Bromide (Br-)
Sodium thiosulfate (Na2S2O3)
Chemistry is found in just about every aspect of our lives—after all, every substance found on Earth is a combination of about 120 elements. So it comes as no surprise that photography—although mostly digital in this modern age—is based very heavily on the use of chemistry. In fact, the increased knowledge of chemistry was a major factor in the improvement of photography. It proved to be vital for people like Nicéphore Niépce, Louis Daguerre, and George Eastman, who invested years into learning chemistry in order to improve photography. Their work definitely paid off—as today over 2.5 billion people own some form of a camera.
Evolution and Improvement
In 1839, William Henry Fox Talbot invented a process that creates permanent paper negatives. Although it wasn't as clear and accurate as the daguerreotype, it went on to become the basis for modern photography.
Dr. Richard Leach Maddox invented the use of gelatin instead of glass as the photographic plate. Charles Bennett created the dry plate method based on Maddox's invention. He found that prolonged heating of gelatin-silver bromide emulsion would result in an increased sensitivity to light.
The new process allows innovators like George Eastman to further enhance the product. In 1889, Eastman introduced roll film, which is still used to this day.
Developing Black and White Film
The role of gelatin is vital to the development process. By swelling, the gelatin allows for processing chemicals to reach the silver-halide grains while still keeping all the grains in place.
Step 1: The film is placed in a developing agent. It is a reducing agent that turns the silver ions into silver metal. The grains exposed to light will develop more rapidly and become pure silver, while the unexposed ones remain as silver-halide crystals.
Step 2: The film is then rinsed out in order arrest the development process.
Step 3: A fixer is applied to dissolve the silver-halide crystals while leaving the silver on the film.
Step 4: The film is then rinsed out to extract all of the processing chemicals. Finally, the film is dried, and the individual exposures are split into negatives.
Step 5: The negative is printed onto light sensitive photographic paper. The final product is a positive image that looks normal to the human eye.
Color With Purpose!
Sepia, a popular effect used in modern photography, was originally used to preserve photographs. As film improved, the effect was no longer needed.
In 1935, George Eastman introduced Kodachrome film to the public. With this invention, amateurs could now take colored photographs.
However, developing Kodachrome films is a very labor intensive job. The process includes a rigorous 17 steps including separate developer solution for each of the three pigment colors—cyan, magenta, and yellow.
1942 saw Kodak release the world's first truly color negative films to the public. "Kodacolor" had a layer sensitive to the primary colors of light: red, green, and blue.
In contrast to black-and-white negatives, developing color film is a very complicated process and strenuous process. The colors are produced by a subtractive color formation system. This means that each one of the pigment colored dyes (cyan, magenta, and yellow) controls one of the primary colors (red, blue, and green. Cyan controls red, magenta controls green, and yellow controls red
Exposure Chemistry
When the shutter of a camera is exposed to light, a latent image is formed. This means that until the image is developed, you can't detect its presence.
The spectral sensitizer of the film grain absorbs the photons of light. When this occurs, the energy of an electron can be transferred to the conduction band. Here, the electron can join the silver-halide lattice to form an atom of silver.
A stable latent image is formed when two to four atoms in a silver-halide grain are of pure silver.
The process is very similar in color film—the same thing occurs for each of the three layers.
Thanks for watching!
By: Swetha Angara
Mrs. McCarthy, Period 1
The use of chemicals in photography has largely been reduced by the invention of digital cameras. However, lomography, a type of film photography, is a passion for many artists. SLR (single-lens reflex) cameras are to this day used by professional photographers and amateurs alike. Most movies are still shot with the standard 35 mm film as opposed to digital cameras. After all, digital photography is based largely on film photography. Chemistry laid the groundwork for such innovations in photography, as it did for so many other things.
Application of Chemistry: Photography
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