Glossary |
Terms that are on use on this site.
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| Shooting distance (camera distance) | The distance from the film plane (focal plane) to the subject. The position of the film plane is indicated on the top of most cameras by a \"line though a circle\" symbol. |
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| Silent Wave Motor | Nikon's unique Silent Wave Motor (SWM) technology converts "traveling waves" into rotational energy tp focus the optics, allowing accurate, uncommonly quite high-speed autofocusing. Standard on all AF-S Nikkors, SWM technology has enjoyed univeral praise from porfessional photographers.
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| Spherical aberration | This aberration exists to some degree in all lenses constructed entirely of spherical elements. Spherical aberration causes parallel light rays passing through the edge of a lens to converge at a focal point closer to the lens than light rays passing through the center of the lens. (The amount of focal point shift along the optical axis is called longitudinal spherical aberration.) The degree of spherical aberration tends to be larger in large-aperture lenses.
A point image affected by spherical aberration is sharply formed by light rays near the optical axis but is affected by flare from the peripheral light rays (this flare is also called halo, and its radius is called lateral spherical aberration). As a result, spherical aberration affects the entire image area from the center to the edges, and produces a soft, low-contrast image which looks as if covered with a thin veil.
Correction of spherical aberration in spherical lenses is very difficult. Although commonly carried out by coming two lenses-one convex and one concave-based on light rays with a certain height of incidence (distance from the optical axis), there is a limit to the degree of correction possible using spherical lenses, so some aberration always remains. This remaining aberration can be largely eliminated by stopping down the diaphragm to cut the amount of peripheral light. With large aperture lenses at full aperture, the only effective way to thoroughly compensate spherical aberration is to use an aspherical lens element. |
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| Stop/diaphragm/aperture | The opening which adjusts the diameter of the group of light rays passing through the lens. In interchangeable lenses used with single lens reflex cameras, this mechanism is usually constructed as an iris diaphragm consisting of several blades which can be moved to continuously vary the opening diameter. With conventional SLR camera lenses, the aperture is adjusted by turning an aperture ring on the lens barrel. With modern camera lenses, however, aperture adjustment is commonly controlled by operating an electronic dial on the camera body. |
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| Subject distance | The distance from the lens’ front principal point to the subject. |
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| Super Integrated Coating | To enhance the performance of its optical lens elements, Nikon employs an exclusive multilayer lens coating that helps reduce ghost and flare to a negligible level.
Nikon Super Integrated Coating achieves a number of objectives, including minimized reflection in the wider wavelength range and superior color balance and reproduction. Nikon Super Integrated Coating is especially effective for lenses with a large number of elements, like our Zoom-NIKKOR lenses.
Also, Nikon\'s multilayer coating process is tailored to the design of each particular lens. The number of coatings applied to each lens element
is carefully calculated to match the lens type and glass used, and also to assure the uniform color balance that characterizes NIKKOR lenses. This results in lenses that meet much higher standards than the rest of the industry. |
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| Super Spectra coating | All EF lenses are coated in accordance with Canon’s own standards, which are even more strict than the CCI tolerances set by the ISO (International Standards Organization), and the variety of single and multilayer coatings used are selected to optimally match the refraction of the lens to which it is being applied. Named Super Spectra coating by Canon, this process features a high permeation rate, ultraviolet ray filtering, highly durable surface hardness and features and stable characteristics. The superior imaging characteristics realized by these exacting coating procedures includes sharp, vivid images with high contrast, uniform color balance throughout the EF lens lineup, and true color reproduction that does not change over years of use. |
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| Super UD lenses | The high cost of synthetic fluorite crystal production makes fluorite lenses extremely expensive. One answer was found in the latter half of the 1970’s with the appearance of UD (ultra low dispersion) glass that could provide characteristics similar to fluorite but at a lower cost. While the indexes of refraction and dispersion of UD glass do not equal that of fluorite, they are significantly lower than those of other types of optical glass. Moreover, UD glass does display partial dispersion characteristics similar to fluorite. The selection of the proper lens element combination in consideration of the intended focal length and other factors can provide close to the same effect as fluorite, (two UD lens elements are equivalent to one fluorite element). Another breakthrough was made in 1993 when Super UD glass was introduced as a new material that achieves almost the same performance as fluorite while achieving a new balance of greater cost reduction and even higher quality. |
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| Superior quality across the total image | To achieve a high level of sharpness both at the center and out to the edges of an image when shooting with a telephoto lens, it is desirable for the index of refraction of the front convex lens element to be as small as possible. Accordingly, the use of fluorite with its low index of refraction effectively improves image quality over the total image area. |
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| Symmetrical type lens | In this type of lens, the lens group behind the diaphragm has nearly the same configuration and shape as the lens group in front of the diaphragm. Symmetrical lenses are further classified into various types such as the Gauss type, triplet type, Tessar type, Topogon type and orthometer type. Of these, the Gauss type and its derivations is the most typical configuration used today because 1) its symmetrical design allows well-balanced correction of all types of aberrations, and 2) a comparatively long back focus can be achieved.
The Canon 50mm f/1.8 released back in 1951 succeeded in eliminating the comatic aberration which was the sole weak point of Gauss type lenses of that day, and thus became famous as a historical landmark lens due to the remarkable improvement in performance it afforded. Canon still uses a Gauss type construction in current lenses such as the EF 50mm f/1.8 II, EF 50mm f/1.4 USM and EF 85mm f/1.2L USM. The Tessar and triplet type symmetrical configurations are commonly used today in compact cameras equipped with single focal length lenses. |
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