Sony Alpha E-Mount Sonnar T* FE 55mm f/1.8 ZA OSS Lens
Impressive Carl Zeiss Sonnar T* (T-Star) optical performance
in a versatile 55mm focal length with a large f/1.8 aperture.
The Sonnar T* FE 55mm F1.8 ZA features renowned Carl Zeiss contrast and resolution brings out the best in Alpha full frame E-mount bodies. The T* coating works with an innovative optical design to suppress internal reflections, for sublime contrast from highlights to deep blacks.
In keeping with the Sonnar concept a large f/1.8 maximum aperture can produce beautiful full-frame background bokeh, but you also have the option of stopping down for extended depth-of-field. A bright lens like this is also an advantage when shooting indoors or outdoors in low light. Linear motor driven internal focusing is smooth and quiet, and a dust and moisture resistant design ensures consistently reliable performance.
Fast F1.8 maximum aperture
The F1.8 aperture consistently provides outstanding performance and lets you take full advantage of the extra speed and brightness it provides. Whether you need the large aperture to shoot in low light, to achieve suitable shutter speeds for shooting action, or for creative control of background defocusing, the SEL55F18Z will reward you with stunning resolution and contrast where it counts.
A compact mid-range zoom that delivers outstanding performance
This compact, high-performance 55mm full frame format mid-range zoom lens has been specifically designed bring out the full performance potential of the Alpha full-frame E-mount camera bodies. True to the "Sonnar" concept, the SEL55F18Z offers superior sharpness and contrast in a compact lens.
Dust and moisture resistant design
Critical areas of the lens exterior feature dust and moisture resistant seals that help to ensure professional reliability even in tough environmental conditions.
Unmatched T* (T-star) coating
The T* (T-star) coating contributes to typically outstanding Carl Zeiss image quality, with high contrast and uniformly excellent resolution right out to the image edges. The coating subdues reflections at the lens surfaces, increasing transmission and minimizing flare and ghosting that can compromise rendering. Natural color reproduction and impressive presence give subjects a lifelike quality. Five aspherical elements and one ED (Extra-low Dispersion) glass element in an advanced optical design reduce aberration and distortion to a minimum.
Aspherical lens elements
Spherical aberration is a slight misalignment of light rays projected on the image plane by a simple spherical lens, caused by differences in refraction at different points on the lens. That misalignment can degrade image quality in large-aperture lenses. The solution is to use one or more specially shaped "aspherical" elements near the diaphragm to restore alignment at the image plane, maintaining high sharpness and contrast even at maximum aperture. Aspherical elements 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, thus reducing overall lens size and weight.
ED (Extra-low Dispersion) glass element
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. To counter such problems, ED glass was developed and is included in select lenses. It dramatically improves chromatic aberration at telephoto ranges, and provides superior contrast across the entire image, even at large aperture settings.
Only the middle groups of the optical system are moved to achieve focusing, which leaves the total length of the lens intact. 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.
In general, if an aperture uses 7 or 9 aperture blades, then the shape of the aperture becomes a 7-sided or 9-sided polygon as the aperture is made smaller. However, this has a certain undesirable effect in that the defocusing of point light sources appears polygonal and not circular. Alpha 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.