LYCOS RETRIEVER 
Lens: Images
built 605 days ago
Chromatic aberration is caused by the dispersion of the lens material—the variation of its refractive index [N] with the wavelength of light. Since, from the formulae above, f is dependent upon n, it follows that different wavelengths of light will be focused to different positions. Chromatic aberration of a lens is seen as fringes of colour around the image. It can be minimised by using an achromatic doublet (or achromat) in which two materials with differing dispersion are bonded together to form a single lens. This reduces the amount of chromatic aberration over a certain range of wavelengths, though it does not produce perfect correction. The use of achromats was an important step in the development of the optical microscope.
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The LEICA D VARIO-ELMARIT lens comprises 16 elements in 12 groups,including two aspherical lenses. It provides high definition image renderingthat conveys even the finest details and nuances. It minimizes distortion and peripheral vignetting at the wide end. And to draw the best opticalperformance out of this compact lens, a large-diameter aspherical glass moldedlens is ... incorporated. With the LEICA D VARIO-ELMARIT, users can now experience the unique performance of Leica optical technology in the world of digital photography.
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A focal length is the distance from the lens to an image the lens makes of a distant object. If an object is farther than one focal length (10 inches [25 cm]) from the lens, the lens can bend all the light that arrives from one point on the object until it comes back to a point on the other side of the lens. This point is a point on the image of the object. If you put white paper at the place where the light rays meet, an image will appear on the paper. An image that can be focused on a piece of paper is called a real image.
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Convex lenses produce an image of an object at infinity at their focus; if the sun is imaged, all the infrared energy incident on the lens is concentrated on the small image. A large lens will concentrate enough energy to heat an inflammable object on which the image falls to burning point. Such lenses, which do not need to be even approximately optically accurate, have been used as burning-glasses for hundreds of years. A modern application is the use of relatively large lenses to concentrate solar energy on relatively small photovoltaic cells, harvesting more energy without the need to use larger, more expensive, cells.
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Sporting a lightweight and compact construction, it provides optimum lens performance via the very latest optical technology. Four SLD glass elements are used for precise correction of chromatic aberrations. High image quality is assured throughout the entire zoom range. It is ... equipped with HSM (Hyper Sonic Motor) with full-time manual focus override, and is compatible with Sigma 1.4x EX DG and 2x EX DG APO Tele-Converters.
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If the lens equation yields a negative image distance, then the image is a virtual image on the same side of the lens as the object. If it yields a negative focal length, then the lens is a diverging lens rather than the converging lens in the illustration. The lens equation can be used to calculate the image distance for either real or virtual images and for either positive on negative lenses. The linear magnification relationship allows you to predict the size of the image.
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