Panchromatic film
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Panchromatic film is a type of black-and-white photographic film that is sensitive to all wavelengths of visible light. A panchromatic film therefore produces a realistic image of a scene. Almost all modern photographic film is panchromatic, but some types are orthochromatic and are not sensitive to certain wavelengths of light. As naturally prepared, silver halide emulsions are much more sensitive to blue and UV light than to green and red wavelengths. The German chemist Hermann W. Vogel found out how to extend the sensitivity into the green, and later the orange, by adding sensitising dyes to the emulsion. However, his technique was not extended to achieve a fully panchromatic film until the early 1900s, shortly after his death. Panchromatic stock for still photographic plates became available commercially in 1906.[1]
Orthochromatic film proved troublesome for motion pictures, rendering blue skies as perpetually overcast, blue eyes nearly white, and red lips nearly black. To some degree this could be corrected by makeup, lens filters, and lighting, but never completely satisfactorily. But even those solutions were unusable for additive color motion picture systems like Kinemacolor and Prizma color, which photographed on black and white stock behind alternating color filters. Eastman Kodak, the leading supplier of motion picture film, introduced a panchromatic film stock in September 1913, available on special order for photographing color motion pictures in additive systems.[2] Cameramen began using it for black and white films too in 1918, primarily for outdoor scenes. The company introduced Kodak Panchromatic Cine Film as a regular stock in 1922.[3] The first feature film to be photographed entirely on panchromatic stock was The Headless Horseman (1922).[4] But panchromatic stock was more expensive, and not until the prices were equalized in 1926 did it become used more widely than orthochromatic stock. Kodak discontinued manufacturing general-purpose orthochromatic motion picture film in 1930.[5]
Digital panchromatic imagery of the Earth's surface is also produced by some modern satellites, such as QuickBird and IKONOS. This imagery is extremely useful, as it generally is of a much higher resolution than the multispectral imagery from the same satellite. For example, the QuickBird satellite produces panchromatic imagery having a pixel equivalent to an area 0.6m x 0.6m, while the multispectral pixels represent an area of 2.4m x 2.4m.
[edit] References
- ^ Ralph E. Jacobson et al., The Manual of Photography: Photographic and Digital Imaging, 9th ed., Focal Press, p. 208. ISBN 9780240515748.
- ^ Richard Koszarski, An Evening's Entertainment: The Age of the Silent Feature Picture, 1915-1928, University of California Press, 1994, p. 140. ISBN 9780520085350.
- ^ Kodak: Chronology of Motion Picture Films, 1889 to 1939.
- ^ Richard Koszarski, An Evening's Entertainment: The Age of the Silent Feature Picture, 1915-1928, University of California Press, 1994, p. 140. ISBN 9780520085350.
- ^ Kodak: Chronology of Motion Picture Films, 1889 to 1939.
[edit] See also
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