Kodachrome #3: Optics [excerpt]

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• published: 26 Apr 2010
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The Muslim scientist Ibn al-Haytham (965-1040 AD), known as Alhacen or Alhazen in the West, developed a broad theory of vision based on geometry and anatomy in his 1021 Book of Optics. Al-Haytham postulated that every point on an illuminated surface radiates light rays in all directions, but that only one ray from each point can be seen: the ray that strikes the eye perpendicularly. The other rays strike at different angles and are not seen. He described the pinhole camera and invented the camera obscura, which produces an inverted image, using it as an example to support his argument. This contradicted Ptolemys theory of vision that objects are seen by rays of light emanating from the eyes. Alhacen held light rays to be streams of minute energy particles that traveled at a finite speed. He improved Ptolemys theory of the refraction of light, and went on to discover the laws of refraction. He also carried out the first experiments on the dispersion of light into its constituent colors. His major work Kitab al-Manazir (Book of Optics) was translated into Latin in the Middle Ages, as well his book dealing with the colors of sunset. He dealt at length with the theory of various physical phenomena like shadows, eclipses, the rainbow. He also attempted to explain binocular vision, and gave an explanation of the apparent increase in size of the sun and the moon when near the horizon, known as the moon illusion. Because of his extensive experimental research on optics, Ibn al-Haytham is considered the father of modern optics. Ibn al-Haytham also correctly argued that we see objects because the suns rays of light, which he believed to be streams of tiny energy particles travelling in straight lines, are reflected from objects into our eyes. He understood that light must travel at a large but finite velocity, and that refraction is caused by the velocity being different in different substances. He also studied spherical and parabolic mirrors, and understood how refraction by a lens will allow images to be focused and magnification to take place. He understood mathematically why a spherical mirror produces aberration. Avicenna (9801037) agreed that the speed of light is finite, as he observed that if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite. Abū Rayhān al-Bīrūnī (9731048) also agreed that light has a finite speed, and he was the first to discover that the speed of light is much faster than the speed of sound. In the late 13th and early 14th centuries, Qutb al-Din al-Shirazi (12361311) and his student Kamāl al-Dīn al-Fārisī (12601320) continued the work of Ibn al-Haytham, and they were the first to give the correct explanations for the rainbow phenomenon. ______________________________________________ Kodachrome is the trademarked brand name of a type of color reversal film that was manufactured by Eastman Kodak from 1935 to 2009. Kodachrome was the first successfully mass-marketed color still film using a subtractive method, in contrast to earlier additive screenplate methods such as Autochrome and Dufaycolor, and remained the oldest brand of color film. Over its 74-year production, Kodachrome was produced in formats to suit various still and motion picture cameras, including 8mm, Super 8, 16mm, and 35mm for movies and 35mm, 120, 110, 126, 828, and large format for still photography. It was for many years used for professional color photography, especially for images intended for publication in print media. Kodachrome requires complex processing that cannot practically be carried out by amateurs. The film is sold with processing included in the purchase price except in the United States, where a 1954 legal ruling prevents this. As digital photography progressively reduced the demand for film in the first decade of the 21st century, Kodachrome sales steadily declined. On June 22, 2009 Eastman Kodak Co. announced the end of Kodachrome production, citing declining demand. Many Kodak and independent laboratories once processed Kodachrome, but only one Kodak certified facility remains: Dwaynes Photo in Parsons, Kansas, where existing film stock will be developed until the end of 2010.