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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Photo. History of invention and production
Directory / The history of technology, technology, objects around us Photography is the acquisition and storage of an image using a photosensitive material or a photosensitive matrix in a camera.
Among the many amazing inventions made in the XNUMXth century, photography is far from the last place - an art that made it possible to make an instant image of any object or landscape. Photography originated at the border of two sciences: optics and chemistry, because to obtain prints it was necessary to solve two complex problems. Firstly, it was necessary to have a special light-sensitive plate capable of perceiving and holding an image. Secondly, it was necessary to find a special device that would clearly project the image of the objects being filmed onto this plate. Both were created only after much trial and error. The miracle of photography was not immediately given to people in the hands, and at different times, many inventors from different countries enthusiastically dealt with this problem. Approaches to it can be found in the works of medieval alchemists. One of them, Fabritius, once mixed common salt in his laboratory with a solution of silver nitrate and obtained a milky white precipitate that turned black from sunlight. Fabricius investigated this phenomenon and in his book on metals, published in 1556, reported that with the help of a lens he obtained an image on the surface of a deposit now known as silver chloride, and that this image became black or gray depending on the duration of its illumination by solar radiation. rays. It was the first experience in the history of photography. In 1727, a doctor from Halle, Johann Schulz, made experiments on a sunny day with a solution of silver nitrate and chalk, the mixture of which he illuminated in a glass vessel. When the vessel was exposed to sunlight, the surface of the mixture immediately turned black. On shaking, the solution turned white again. By means of pieces of paper, Schulz obtained silhouettes on the surface of the liquid, by shaking, he destroyed them and obtained new patterns. These original experiments seemed to him only fun, and another hundred years passed before the property of silver chloride he noticed was thought of using in the manufacture of photographic plates. The next page in the history of photography is associated with the name of Thomas Wedgwood. He laid plant leaves on paper moistened with a solution of silver nitrate. At the same time, the part of the paper covered with leaves remained light, while the illuminated part turned black. The result of this experience was a white silhouette on a black background. However, these images could only be viewed by candlelight, as they deteriorated when exposed to sunlight. Wedgwood tried the solution on the skin and found that the images on it appear faster. (At that time, this phenomenon remained unexplained. It was not until the late 30s that it was found that the tannic acid contained in the skin significantly accelerates the development of the image.) In 1802, Wedgwood published the results of his experiments. Gradually, he learned to obtain contour images on paper, skin and glass within three minutes when exposed to the sun, and for several hours when exposed to the shade. But these shots couldn't stand the sunlight because they weren't captured. It wasn't until 1819 that John Herschel found a substance that strengthened the photographic image. It turned out to be sodium sulphate. It would seem that photography had to take the last step in order to take place fully as an art, but this step was taken only twenty years later. In the meantime, the search for inventors has taken a different path. In 1813, the French artist Niépce, who was credited with inventing the camera, began experimenting with photographic plates. Around 1816, he came up with the idea of taking an image of objects using the so-called camera obscura. This chamber has been known since ancient times. In its simplest form, it is a light-tight box tightly closed on all sides with a small opening. If the wall opposite the hole is made of frosted glass, then an inverted image of objects in front of the camera is obtained on it. The smaller the hole, the sharper the contours of the image and the weaker it is.
For centuries, the effects observed in the camera obscura have delighted nature lovers. In 1550, Cardan built a chamber in Nuremberg with a large aperture containing a lens. Thus, he got a brighter and clearer image. This was an important improvement, since the lens collected rays well and greatly improved the observed effect. It was such a dark box with a very small hole and a lens on one side and a photosensitive plate on the other that Niépce decided to use for the projection of the image. It was the first ever camera. In 1824, Niépce succeeded in solving the problem of fixing images obtained in a camera obscura. Unlike his predecessors, he did not work with silver chloride, but made experiments with mountain resin, which, under the influence of light, has the ability to change some of its properties. For example, in the light it ceased to dissolve in some liquids, in which it dissolved in the dark. Having covered a copper plate with a layer of mountain resin, Niepce inserted it into a camera obscura and placed it in the focus of a magnifying glass. After a rather long exposure to light, the plate was taken out and immersed in a mixture of oil and lavender oil. In places containing the action of light, mountain resin remained intact, while in the rest it was dissolved in the mixture. Thus, places completely covered with resin represented illuminated places, and places covered only in part - penumbra. It took at least 10 hours to get the picture, since the resin changed very slowly under the influence of light. It is clear that this method could hardly be called perfect, and Niepce continued to search. In 1829 he joined forces with Louis-Jacques Daguerre, a former officer and decorator at the Parisian theater who worked on the same problems. He soon died, and Daguerre continued his research alone. He already had at his disposal the camera invented by Niépce, but still did not know how to obtain a photosensitive plate. A whole series of amazing coincidences finally led him on the right path. One day, Daguerre accidentally placed a silver spoon on metal coated with iodine, and noticed that the image of a spoon turned out on the metal. Then he took a polished silver plate and subjected it to the action of iodine vapors in order to obtain silver iodide in this way. On the plate he put one of Niépce's photographs. After some time, a copy of the picture formed on it, but very obscure, so that it could only be distinguished with difficulty. Nevertheless, it was an important result that discovered the photographic properties of silver iodide. Daguerre began to look for a way to develop the resulting images. Another happy accident led to an unexpected success. Once Daguerre took from a dark room a plate left there, with which he had worked the day before, and to his great surprise he saw a weak picture on it. He suggested that some substance acted on the plate and showed during the night an image invisible the day before. There were a lot of chemicals in the dark room. Daguerre began to search. Every night he put a new record in the closet, and every morning he took it out, along with one of the chemicals. He repeated these experiments until he removed all the chemicals from the room, and put a new record on the already empty shelf. To his surprise, in the morning this plate was also developed. He carefully examined the room and found some spilled mercury in it: its vapors were the chemical developer.
After that, Daguerre could already without any difficulty develop all the details of the photographic process - using a camera, he received weak images on plates coated with silver iodide, and then developed them with mercury vapor. The result was remarkably clear images of objects with all the fine details and halftones. Years of searching ended with a remarkable discovery.
On August 10, 1839, a large meeting took place in Paris with the participation of members of the Academy of Sciences. Here it was announced that Daguerre had discovered a way to develop and fix photographic images. This message made a huge impression. The whole world was discussing the possibilities opened up by the new achievement of human thought. The French government bought the secret of Daguerre's invention and gave him a lifetime pension of 6000 francs. The son of Niépce was not forgotten either. Soon, kits for photographing according to the Daguerre method appeared on sale (this method became known as daguerreotype). Despite the high price, they were sold out in a short time. But soon the public felt a strong cooling towards this invention. Indeed, daguerreotype, although it gave good results, required a lot of work and considerable patience. The work of a daguerreotypist began with the cleaning and polishing of a silver-plated copper plate. This work had to be done very carefully: first with alcohol and cotton wool, and then with iron oxide and soft leather. In no case should you touch the plate with your finger. The final polishing was done just before shooting. After that, the silver plate was made sensitive to light. To do this, it was placed in the dark in a box with dry iodine. Depending on what they were going to shoot - a landscape or a portrait - the duration of treatment with iodine vapor was not the same. After that, the plate became photosensitive for several hours, and it was placed in a cassette. The cassette was a small flat wooden box with two movable walls - the back one opened on hinges in the form of a door, and the front one went up and down on special skids. Between these doors there was a plate. The first cameras were improved pinhole cameras. In a box open on one side, another box moved back and forth, which could be held in a certain position with a screw. On the front wall of this box was a lens or glass slide, and on the back side was a frosted glass. Soon Charles Chevalier began to use two lenses instead of one, thus constructing the first lens. The rays from an external object, passing through the lens, stopped on the frosted glass, and at the proper distance of the latter from the object, its distinct image was presented on it. Greater or lesser distinctness of the image was achieved by moving the inner box away or approaching and rearranging the lens. When the desired clarity was achieved, a cassette was placed in place of the frosted glass so that when inserted into the camera, the surface of the plate would be exactly in the place that the frosted glass occupied at the moment when the image of the object was most distinct on it. Then they took out the front cover of the cassette and started shooting. The first sessions were so tiring, the conditions were so bad, the records reacted so slowly, that it took a lot of effort to find people willing to act. I had to sit motionless for 20 minutes under the scorching rays of the sun in order to get a portrait that was successful according to the then concepts. The images of the eyes in the first portraits succeeded with great difficulty, therefore, in the early daguerreotypes, we see faces with closed eyes. At the end of the shooting, the cassette was closed and sent to a dark room. Here, by the light of a candle, the plate was taken out. On it one could see a barely perceptible image of the object. In order for it to become clear and distinct, it had to be manifested. This operation was carried out using mercury vapor. A little mercury was poured into a wooden box with a copper bottom and a plate was placed in it with the image down. To speed up the process, a burning alcohol lamp was placed below. Mercury began to evaporate intensively and developed the image. The daguerreotyper observed this process from the side through a special window. After the image appeared clearly enough, the plate was removed. Where the light had the strongest effect, the combination of iodine with silver was weakened to the greatest extent, and therefore mercury stuck here in tiny droplets that formed a white surface. In halftones, there were more obstacles for the addition of mercury, and in dark places, mercury could not stick to the undecomposed layer of silver iodide at all. That is why the penumbras came out more or less grayish, and pure silver seemed completely black. To remove the remnants of unreacted silver iodide, the plate had to be fixed. To do this, it was placed in a solution of sodium sulphate, which dissolved silver iodide, which had not undergone the action of light. Finally, the plate was washed in water and dried. As a result of all these manipulations, an amazingly clear image was obtained on the plate, in which every detail was transmitted with amazing clarity. But in order for the image to last longer, it had to be strengthened. To do this, the plate was doused with a weak solution of gold chloride and boiled in an alcohol flame. During this reaction, the chlorine of gold chloride combined with silver, and gold was released in the form of a metal and covered the image with the thinnest protective film. This operation also eliminated the unpleasant specularity of the silver. This is how photography appears before us in the first years of its existence. From our brief description, it is clear that this was not only a tedious, but also a very unhealthy exercise. Nevertheless, photography immediately gained many ardent fans and enthusiasts. They were ready to inhale vapors of iodine or mercury for hours, watching with enthusiasm how the image mysteriously appears on the plates. It is to them that this art owes its rapid improvement. First of all, experiments were resumed with paper impregnated with a photosensitive composition - it began to be called photographic paper. These experiments were carried out at the beginning of the century by Wedgwood. In the same 1839, Fock Talbot found that if photographic paper, which was even briefly exposed to light, was treated with gallic acid, the image appeared very quickly. In the same way that mercury produces an image on a silver surface, so galusic acid produced an image on paper. The following year, Professor Goddard from London discovered that when silver iodide was replaced with silver bromide, the sensitivity of the photolayer increased several tens of times. Thanks to this, the time required to capture the subject decreased immediately from 20 minutes to 20 seconds. At the same time, Claudet found that bromine greatly increases the sensitivity of iodized silver plates, so that a few seconds were enough to obtain an image. After these discoveries, the development of photography in the modern sense of the word became possible. In photography, silver combined with iodine, chlorine and bromine played a major role in producing the image. Under the action of light, the compounds decomposed and silver was released in the form of tiny particles, forming a drawing substance, just like mercury in daguerreotype. All the chemical reactions that take place during photography can be demonstrated by a few simple experiments. If a few drops of silver nitrate are poured into a test tube with a solution of common salt, then as a result of the reaction of these two substances, a white cheesy precipitate of silver chloride is formed. In sunlight, this precipitate loses its white light in a short time and becomes first violet, then gray, and finally black. The fact is that under the action of light, silver chloride decomposes, and metallic silver is released. However, only those layers that are closer to the light undergo this change. If you add a few drops of sodium sulfate to the solution, most of the silver chloride will gradually dissolve. Only flakes of metallic silver released under the action of light will remain undissolved. In these reactions, the entire course of operations is represented in photography. To prepare photographic paper, a good white sheet of writing paper was taken and soaked in a 10% sodium chloride solution, dried, and a solution of silver nitrate was spread over the surface. As a result, a photosensitive layer of silver chloride was formed on the paper. The finished sheet was placed in an opaque cassette and photographed in the same manner as described above. At the same time, after developing on paper, a visible image of the object was obtained, but not direct, but reversed, that is, the brightest places on it came out the darkest, and the darkest ones remained light. This was because wherever the photolayer was exposed to intense light, the greatest amount of black metallic silver was released. On the contrary, where the effect of light was insignificant, white silver chloride was preserved. This image was fixed by washing the leaf in a solution of sodium sulphate. But, obviously, it was inconvenient to use such a photograph, which gave a completely reverse image of light and shadow. It was used to obtain positive prints. To do this, it was placed in the dark on a sensitive sheet of photographic paper in a copy frame, covered with a glass plate, and exposed to light. The latter penetrated through the negative image laid on top. It passed most easily through completely light places, weaker through halftones and almost did not penetrate shadows at all. Therefore, the required positive image was obtained on the lower sheet of sensitive paper, which, after sufficient exposure to light, was taken out and strengthened. However, for all these operations, paper is not a suitable material, as it has a rough structure and prevents the passage of light. Clear glass would have been the best material for its transparency, but it was not able to absorb chemicals, so turning it into a photosensitive plate was not as easy as paper. A way out of this difficulty was found quite quickly - the glass plate was covered with a transparent thin adhesive film capable of holding the photosensitive layer. At first, egg whites were used for this, and then collodion. The last method was discovered in 1851 by Scott Archer. The photographic collodion consisted of a solution of cotton rattling paper in ether with alcohol and was a colorless slimy liquid that quickly dried in thin layers, leaving a transparent film. To obtain a glass photographic plate, cadmium iodide was added to the collodion solution. After that, a clean glass plate was taken and a sufficient amount of collodion was poured onto it. When the collodion dried up to a thick mass, the plate was immersed in a solution of silver nitrate saturated with silver iodide. In this reaction, iodine and bromine combined with silver, forming silver iodide and bromide, which was deposited in a layer of collodion. On the contrary, nitric acid released from the silver salt combined with cadmium. Thus, the plate was covered with a photosensitive layer and was ready for shooting. To develop the image, it was treated with a solution of pyrogalusic acid or a solution of iron sulphate (water + iron sulphate + acetic acid + alcohol). The acetic acid somewhat slowed down the reaction so that the development did not go too fast. Fixation took place, as before, with a solution of sodium sulphate. For copying and obtaining the final image, photographic paper coated with silver chloride served. Collodion photography marked the beginning of modern photography; since that time, it has become possible to easily and quickly get good, clear pictures. Author: Ryzhov K.V.
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