Pentax 21870 DA 50-200mm F/4-5.6 AL Weather Resistant Lens Weather-resistant to handle damp, inclement conditions. Flexible 4X zoom coverage in the telephoto range. The PENTAX-original Quick-Shift Focus System allows instant switching from autofocus to manual focus operation. An Extra-low Dispersion glass lens element and two aspherical lens elements offer superior sharpness with minimum chromatic and spherical aberration. Simple and functional design improves operability and body-based depth of field control.