I'm a fan of constant aperture zooms myself. I'm partial to my Tamron 17-50 f/2.8, and your camera uses pretty much the same sensor my camera does (I have a Pentax K5), and that's been my go to at cons. I've tried various primes, but I keep coming back to that lens. I know the Sigma version of it has OS and from what I hear is slightly sharper, so I would consider that one as well or the Nikon branded version of it.
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