Opteka

Super 500mm/1000mm f/8 Manual Telephoto Lens for Pentax K-1, K-S2, K-S1, K-500, KP, K-70, K-50, K-30, K5 IIs, K-7, K-5, K-3 II, K-2, K-X, K20D, K100D, K110D and K10D Digital SLR Cameras

"500mm / 1000mm f/8 Manual Focus Lens is a classic refractor-style T-mount lens, with an aperture diaphragm in the middle of the lens body to stop down the aperture when necessary. However, it is assumed that much of the shooting with such a lens will...