Product DescriptionSony SEL70200G 70-200mm Interchangeable Lens for Sony Alpha Cameras. Angle of View 34°-12° 30' The small size, versatile 35mm focal length, and outstanding overall performance of this Carl Zeiss Sonnar T* lens make it an ideal match for compact 35mm full frame format E-mount bodies. Although the optical design is state-of-the-art, this superb wide angle lens remains true to the original Sonnar concept with a bright F2.8 maximum aperture (“Sonne” means “sun” in German). Three double-sided aspherical elements minimize aberration so that stunning contrast and resolution are maintained right out to the image edges at all apertures. The renowned T* lens coating contributes to natural color reproduction as well. When changing your aperture to defocus the background, the light sources appear blurred. This ‘bokeh’ 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. α 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. Effectively suppress reflections that can cause flare and ghosting with Sony’s original Nano AR Coating technology. This precisely defined regular nano-structure allows accurate light transmission, contributing to high-quality images, even more so than lenses with coatings that use an irregular nano-structure. The reflection suppression characteristic of the Nano AR Coating is superior to conventional anti-reflective coatings, providing a notable improvement in clarity, contrast, and overall image quality. 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 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 “aspherical” 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. Once you’ve adjusted focus to where you want it, pressing this button on the lens barrel will keep the lens locked to that focusing distance. The preview function can also be assigned to this button through the camera’s custom settings. This function allows you to set a limit on the focusing range which can save you time during AF operation as the lens will not ‘hunt’ through the entire focusing range. In macro lenses, this limit can be on either the near or far range (as pictured). In the SAL70200G, the limit is set on far ranges only. In the SAL300F28G, focusing can be limited either to a far range or to a range that you specify yourself.