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.
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.
Dust and Moisture Resistant
The dust and moisture resistance design make this lens appropriate for heavy-duty outdoor use, especially when combined with a camera that employs weather resistant measures.
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.