I had the original 55-300 which has recently run down and looks just as if not better. It's very light and compact for a zoom of this magnitude, but loses half an aperture compared to its predecessor. In practice, I found this irrelevant as I didn't take this lens with me for low light shots anyway. What makes a big difference is its incredibly fast focus speed, the fastest of any Pentax lens I've used by a wide margin.
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