B00SG8KPH6 Opteka 500mm f/6.3 (with 2X- 1000mm) Telephoto Mirror Lens for Pentax K-70, K-50, K-3 II, KP, K-1, K-S2, K-S1, K-500, K-30, K5 IIs, K-7, K-5, K-2, K20D, K100D, K110D and K10D Digital SLR Cameras

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ADVANCED OPTICS: Featuring an optimized design, this lens uses mirrors and a series of 7 optical glass elements in 6 groups to reduce chromatic and spherical aberrations. A anti-reflective coating suppresses lens flare and ghosting for increased contrast and color fidelity.
SUPER ZOOM: Manual focus 500mm or 1000mm with the 2x converter, this lens is not only a superb long range choice, but also performs well in a variety of scenes from sports and surveillance to everyday shooting.
SOLID CONSTRUCTION: Full metal body and rear mount allow this lens to withstand wear and tear much better than plastic lenses while commanding a rugged, solid feel when using.
COMPACT AND LIGHTWEIGHT: Mirrors allows this lens to be much shorter than it would need to be without the mirrors. At 4.7-inches long, this 500mm f/6.3 is one of the shortest telephoto lenses currently available.
COMPATIBILITY: Can be used on all Pentax APS-C and full frame cameras including K-70, K-50, K-3 II, KP, K-1, K-S2, K-S1, K-500, K-30, K5 IIs, K-7, K-5, K-2, K-r, K-x, K-m, K20D, K200D, K100D, K110D and K10D.