Sony DT 11-18mm f/4.5-5.6 Aspherical ED Super Wide Angle Zoom Lens for Sony Alpha Digital SLR Camera Description
Product description DT 11-18mm f/4.5-5.6 Super Wide Zoom Aspherical Lens Elements for wide-angle accuracy ED (Extra-low Dispersion) Glass for sharp, accurate colors Circular Aperture for pleasing defocused effects DT Lens Design for optimum DSLR performance Excellent wide-angle to long telephoto shots Fast Internal Focusing, lens length does not change From the Manufacturer DT 11-18mm F4.5-5.6 Wide Zoom Lens This wide zoom lens offers a range of focal lengths that are indispensable for serious indoor and architectural photography as well as any other situation that demands wide-angle coverage. City scenes, crowded markets, historical ruins . . . all of these are subjects that can benefit from the wide perspectives this lens provides. Technology Circular Aperture When changing your aperture to defocus the background, the light sources appear blurred. This âbokehâ effect of the blurred background can be enhanced with circular aperture blades used in this lens. Conventional aperture blades have flat sides creating unappealing polygonal shaped defocussed points of light. Î± lenses overcome this problem through a unique design that keeps the aperture almost perfectly circular from its wide-open setting to when it is closed by 2 stops. Smoother, more natural defocusing can be obtained as a result. ED (Extra-low Dispersion) glass As focal lengths get longer, lenses built with conventional optical glass have difficulties with chromatic aberration, and as a result images suffer from lower contrast, lower color quality, and lower resolution. ED glass dramatically reduces chromatic aberration at telephoto ranges, and provides superior contrast across the entire image, even at large aperture settings. Super ED glass provides enhanced compensation for chromatic aberration. Aspherical lens elements Aspherical lens design dramatically reduces spherical aberration while also reducing lens size and weight. Spherical aberration is a slight misalignment of the light rays projected on the image plane. This is caused by differences in refraction at different points on conventional spherical lenses which degrade image quality in large-aperture lenses. Specially shaped âasphericalâ elements near the diaphragm restore alignment of light rays at the image plane, maintaining high sharpness and contrast even at maximum aperture and can also be used at other points in the optical path to reduce distortion. Well-designed aspherical elements can reduce the total number of elements required in the lens, thus reducing overall size and weight. Advanced Aspherical (AA) elements are an evolved variant, featuring an extremely high thickness ratio between the center and periphery. AA elements are exceedingly difficult to produce, relying on the most advanced molding technology to consistently and precisely achieve the required shape and surface accuracy, resulting in significantly improved image accuracy and quality. Distance encoder The distance encoder plays an integral part in ADI flash metering, which delivers high precision flash metering that is unaffected by the reflectance of subjects or backgrounds. The distance encoder is a lens component that directly detects the position of the focusing mechanism, and sends a signal to the CPU in order to measure distance to the subject. During flash photography, this data is very useful in calculating how much flash output is appropriate to the scene. Additional Features Internal focusing Only the middle groups of the optical system move to achieve focus, so the overall length of the lens does not change. Other important benefits include fast autofocusing and a short minimum focusing distance. Also, the filter thread at the front of the lens does not rotate, which is convenient if youâre using a polarizing filter. 2008 Sony Electronics, Inc. All rights reserved. Sony, the Sony logo, Alpha, âÎ±â and Super SteadyShot are trademarks of Sony. All other trademarks are trademarks of their respective owners.