I think the best you could do would buy a Tamron 70~200 f2.8. If you absolutely want/need f2.8 @ 300mm, you'll have to search out a second-hand single-focal-length 300 f2.8, most likely a manual focus. If 300 f4 will do (only one and a fraction stops faster than the 55~300) then the Pentax 300 f4 would do. If you must have a zoom, back off 300mm and get the 60~250 f4 at about the same price. However, that only gives a relatively small 50mm more than a 70~200 at the cost of f4 instead of f2.8. A zoom that has f2.8 @ 300mm is simply not available - - I suspect a 70~200 f2.8 will serve you best, Tamron being the only option for K-mount at this time (promised Pentax zoom of 70~200, f2.8 has been delayed, release date uncertain, projected price almost double that of the Tamron).
Last edited by WPRESTO; 10-31-2015 at 04:51 PM.
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