Looking harder at the 20mm primes, either the Nikkor 1.8 or Sigma's new Artsy 20 1.4.
Price is close enough at about a grand.
Obviously the Siggy is a stop faster (or is that a full stop?)
But apparently not as sharp at 1.4 as 1.8 - but nice to be able to open it up just a little more when you really need it.
BUT - size matters - in this case the Sigma is a Bigma lens, bulbous front end (not easy filtering) and almost three times the weight.
Nikkor G is much lighter (and more plasticy according to some reviews) but durable enough - especially if well cared for and used as often as one might expect to use a 20mm prime
DOX scores are exceptional for either of these. There does not seem to be much difference in the IQ reviews - the Sigma is a bigger, heavier, perhaps better built lens, but is it too big? Would I avoid using it? The Nikkor 1.8 would fit into the bag much easier.
Another upside I had not really thought about but I'd get two primes for the price of one when I mount this on my D7100 it is a fast 30mm prime.
I do have some primes - a 35 DX, 60mm Macro, 50mm Siggy Art and 105 AFD macro.
I could spend a grand or two and get a better FX zoom although the one I have isn't all that awful.
Or, spend about a grand and get a super sharp 20mm fast prime that I can use when I need it.
I'm off to an in-store photography show at McBains on Saturday - maybe the Sigma or Nikon reps there will be persuasive enough to get me to open my wallet "ultra wide". There have been Tamron people at this event last time I went, but don't think I've ever seen a Tokina person there - but then I wasn't looking for one.