High-performance Carl Zeiss large-aperture zoom. The SAL-2470Z Carl Zeiss Vario-Sonnar f2.8 24-70mm Zoom Lens is a brilliant all-around performer -- with SSM (Super Sonic wave Motor) design for fast, silent auto-focus, pro-quality Carl Zeiss T coated optics to reduce lens flare, and 17-element design with two aspherical and two ED glass lens elements to minimize distortion and virtually eliminate chromatic aberration. It benefits from the Super SteadyShot image stabilization built into every Sony Î± system DSLR -- and its wide-angle to medium telephoto range in compact, lightweight design is ideal for a wide range of shooting applications (35mm equivalent: 36-105mm).
Vario-Sonnar T* 24-70mm F2.8 ZA SSM Zoom Lens
Brilliant performance in compact design. This superb Carl Zeiss Vario-Sonnar T* Zoom Lens provides large-aperture f2.8 brilliance, all-purpose 24-70mm zoom range and fast, silent auto-focus with SSM (Super Sonic wave Motor) design - plus aspherical and ED glass elements to reduce distortion for superior clarity and color (35mm equivalent: 36-105mm).
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.
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 “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.
Carl Zeiss T* (T-star) coating
Coated optics were pioneered by Carl Zeiss - and this superb lens features the Carl Zeiss T* (T-Star) coating that virtually eliminates lens flare, internal reflection and light scattering that can otherwise occur at glass-to-air surfaces. The T* coating contributes to outstanding image quality, with high contrast and uniformly excellent resolution right out to the image edges. Not simply applied to any lens - the T* symbol only appears on multi-element lenses in which the required performance has been achieved throughout the entire optical path, therefore guaranteeing the highest quality.
Focus hold button
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.
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.
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 you’re using a polarizing filter.
SSM (Super Sonic wave Motor)
SSM is a piezoelectric motor that contributes to smooth and silent AF operation. The motor produces high torque at slow rotation, and provides immediate start and stop responses. It is also extremely quiet, which helps keep autofocusing silent. Lenses that feature SSM also include a position-sensitive detector to directly detect the amount of lens rotation, a factor that improves AF precision overall.
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