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.
Lens-based optical image stabilization
Gyro sensors built into the lens detect even the slightest movement, and the stabilization lens is precisely shifted to counteract any image blur that might occur. The use of precision, quiet linear motors and technology inherited from high-end Sony professional camcorders results in exceptionally quiet, effective image stabilization that contributes to high-quality movies as well as stills.
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.
Compact and lightweight
The SEL50F18 is remarkably compact and lightweight for a large-aperture mid-range telephoto lens (50mm focal length/75mm equivalent in 35mm format). It is convenient to carry around for general photography, and particularly well suited to shooting portraits. The elegant aluminum alloy exterior of this lens affords an appearance that blends beautifully with the graceful design of E-mount bodies, and the engraved focus ring offers sophisticated appearance as well as superior grip and operating feel.
Direct Manual Focus (DMF)
Direct Manual Focus (DMF) allows the user to go directly to manual focusing after autofocus lock-on without having to switch modes. In cases where autofocus has trouble locking onto the subject, or when the user wants to focus at a specific point, DMF facilitates fast, easy fine focus adjustments. This can be particularly useful for portraits in which depth of field can be extremely shallow.