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Encyclopedia :
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PH :
PHO :
Photography (science of) |
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Photography (science of)This page provides information on the science used in all aspects of photography: the camera, its lenses, physical operation of the camera, electronic camera internals, and the process of developing film.
The optical systemLensesA photographic lens is composed of several lenses, to reduce the effects of Chromatic aberation, Coma (Sperical aberation, and to allow focusing, and possibly zooming capabilities. A simple example is the Cooke triplet, which was used in early cameras, but has since been replaced by more complex systems. Another, the Angenieux retrofocus allows the distance between the last lens and the film to be larger than it would be otherwise. This design is necessary for wide angle lenses on manual cameras, since otherwise the last lens would need to be so close to the film so as to interfere with the mirror. Aberrations of any sort can be reduced by using a small aperture and preventing light from striking the edges of the lenses, where the undesirable effects of distortion are minimized. Aberations can be reduced dramatically by using an ashperical lens, but these are more complex to grind than spherical or cylindrical lenses. However, with modern manufacturing techniques the extra cost of manufacturing aspherical lenses is decreasing. To obtain optimum image quality, a camera will not use Fresnel lenses, although this would reduce the weight of lens which can be significant, especially for telephoto zoom lenses. See also the diagram Movement of lenses in an afocal zoom system under Zoom lens. It is harder to correct for chromatic aberation with zoom lenses, as they must be calibrated to focus over a range of focal lengths. Zoom lenses will also generally have a smaller range of f stops than fixed focal length lenses.
Focal Length. The focal length of an optic system of thin lenses is the sum of the focal lengths of each of its parts -- is the thin lens approximation valid for a standard camera lens, say a 50mm lens for the 35mm camera system? if not, how is the focal length determined?
Bokeh and Depth of fieldThe shortest distance an object can be at from the film, while still being within acceptable focus is called the hyperfocal distance, and the distance from the hyperfocal distance to the farthest point at which an object is still in focus is the depth of field. Depth of field is controlled primarily by the aperture; a large aperture will give a lot of blur in the background because light from a point object not in focus will be incident at more angles at the aperture, thus a larger area over the film. Bockeh refers to the quality of the blur in the areas that are not in focus. See also Circle of confusion.
Since this distance is so small (personal experience), generally a tripod is used when the magnification is high or the picture is taken in low light. physics ofautofocusworkings of a typical manual camera systemhow electron overflow in ccd's can lead to blurring and fringing effectschemistry ofdeveloping filmpolaroidsConditions with other practical and scientific concerns to the photographer
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