Pentax SMC 50-135mm f/2.8 ED

Special optical glass, including three ED glass elements, and outstanding coating ensure very good contrast behavior, consistent sharpness right to the edge, and particularly clear reproduction of the finest details.
In addition to the outstanding imaging properties, PENTAX engineers have also raised the mechanical properties of this lens to top level. Built-in ultrasonic motors (Supersonic motors) in the lenses ensure quiet and fast autofocus drive (SDM system only in conjunction with PENTAX K10D; all other PENTAX DSLR cameras use the conventional body-side AF drive for focusing). In addition, this lens is weather sealed and reliably protected against dust penetration. For the coating of the front lenses Pentax uses special fluoride compounds, the SP - "Super Protect" technology. Here, the front lens is coated with a special coating. This nano-technology protects the front lens from dust, fingerprints or greasy residues. If necessary, such contaminants can be easily removed.
The Pentax "Quick Shift Focus System" allows the photographer to change the focus as desired after automatic focusing. This allows direct manual fine-tuning of the focus at any time without switching off the autofocus.