I'm in the market for something a little wider than my Sigma 20mm. Ideally I'd like to stick with a prime lens, although I wouldn't rule out one of the wide zooms. Obviously has to be Nikon Fit. Anybody have the Sigma 15mm f2.8? or the 10mm-20mm zoom? What about the Nikon 16mm f2.8 and 12-24mm f4 Opinions and advice welcome.