Forensic Photography

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Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either chemically by means of a light-sensitive material such as photographic film, or electronically by means of an image sensor.[1] Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. The result in an electronic image sensor is an electrical charge at each pixel, which is electronically processed and stored in a digital image file for subsequent display or processing. The result in a photographic emulsion is an invisible latent image, which is later chemically developed into a visible image, either negative or positive depending on the purpose of the photographic material and the method of processing. A negative image on film is traditionally used to photographically create a positive image on a paper base, known as a print, either by using an enlarger or by contact printing. Photography has many uses for business, science, manufacturing (e.g. photolithography), art, and recreational purposes.


On 1834, in Campinas, Brazil, Hercules Florence, a French painter and inventor, wrote in his diary the word "photographie" to describe his process.[2] As far as can be ascertained, it was Sir John Herschel in a lecture before the Royal Society of London, on March 14, 1839 who made the word "photography" known to the world. But in an article published on February 25 of the same year in a German newspaper called the Vossische Zeitung, Johann von Maedler, a Berlin astronomer, had used the word photography already.[3] The word photography derives from the Greek φωτός (phōtos), genitive of φῶς (phōs), "light"[4] and γραφή (graphé) "representation by means of lines" or "drawing",[5] together meaning "drawing with light".[6]

Precursor technologies
Photography is the result of combining several technical discoveries. Long before the first photographs were made, Chinese philosopher Mo Di and Greek mathematicians Aristotle and Euclid described a pinhole camera in the 5th and 4th centuries BC.[8][9] In the 6th century AD, Byzantine mathematician Anthemius of Tralles used a type of camera obscura in his experiments,[10] Ibn al-Haytham (Alhazen) (965–1040) studied the camera obscura and pinhole camera,[9][11] Albertus Magnus (1193–1280) discovered silver nitrate,[12] and Georges Fabricius (1516–71) discovered silver chloride.[13] Daniele Barbaro described a diaphragm in 1568.[14] Wilhelm Homberg described how light darkened some chemicals (photochemical effect) in 1694.[15] The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, described what can be interpreted as photography.[14] The discovery of the 'camera obscura' that provides an image of a scene is very old, dating back to ancient China. Leonardo da Vinci mentions natural camera obscuras that are formed by dark caves on the edge of a sunlit valley. A hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. So the invention of photography was really concerned with finding a means to fix and retain the image in the camera obscura. This in fact occurred first using the reproduction of images without a camera when Thomas Wedgwood, from the famous family of potters, obtained copies of paintings on leather using silver salts. As he had no way of fixing them, that is to say to stabilize the image by washing out the non-exposed silver salts, they turned completely black in the light and had to be kept in a dark room for viewing. Renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. The camera obscura literally means "dark chamber" in Latin. It is a box with a hole in it which allows light to go through and create an image onto the piece of paper.

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