Exceptionally smooth bokeh with sharp subject matter are the calling cards of the 135mm f/2.8 STF Lens from Sony. Equipped with Smooth Trans Focus technology, this lens uses apodization optics in order to diffuse the edges of out-of-focus elements, rendering them even smoother than a standard lens can produce. The f/2.8 maximum aperture assists in capture images with shallow depth of field, though with the apodization elements this functions as a T4.5. The lens also features a manual focus design with a manual focus distance of 2.9'. Additionally, it features both a ten-blade manual aperture diaphragm and a nine-blade auto aperture diaphragm, both rounded to create smooth bokeh.
This telephoto prime lens is optimized for full-frame A-mount cameras, however it can be used on APS-C models where it will provide a 202.5mm equivalent focal length.
Optical design incorporates Smooth Trans Focus technology, which uses an apodization element that helps to improve the quality of bokeh. This element, which resembles a radially graduated ND filter that tapers from clear in the center to more dense around the edges, produces more circular out-of-focus highlights for more pleasing selective focus and shallow depth of field effects while still rendering the subject in sharp focus.
An aperture range of f/2.8 to f/31 is available, however the implementation of the apodization filter renders this range as T4.5 to T32.
This lens incorporates two separate aperture diaphragms in order to provide more control over operation and image quality. When shooting near wide open, from T4.5 to T6.7, the manual aperture ring offers a rounded ten-blade diaphragm for smoother and more circular bokeh. For ease of use, there is an electronically controlled aperture which has a rounded nine-blade design for smooth out-of-focus elements.
This lens uses a manual focus design to provide tactile control over focusing during use. It can also focus as close as 2.9'.
Compatible with Sony's line of teleconverters, shooters can easily add the 1.4x or 2x versions to create 189mm f/4 [T6.3] or 270mm f/5.6 [T9] optics, respectively.