Laowa 105mm F2 (T3.2) STF Lens (PENTAX). STF stands for Smooth Trans Focus, in reference to its special optical system, which is intended to deliver smooth transitions between crisp in-focus areas and creamy defocused background or foreground areas. This unique manual focus only lens has an integrated apodisation filter that provides superior bokeh rendering and crystal sharp images. Full frame compatible lens featuring 11 elements in 8 groups with a 14 blade aperture* and a minimum focus distance of just 0.9M. All metal alloy construction housing multi-coated glass elements throughout. At a focal length of 105mm and with the inherent softly diffused bokeh, this lens is perfect for portraiture. Suitable for Pentax K mount. Accepts 67mm filters.