[Brightcolours]

Thanks a lot Markus, I guess I triggered this review!   The results are as I was expecting. Clearly I need to replace the Tamron. But it seems I do not have many options. I take landscapes and architectural photos mostly with ND filters (this is some sort of the best of 2016). So I need a lens under 20mm with filter thread. Nikkor AF-S 16-35mm f/4 is not a good optic, Zeisses and Nikkor AF-S 17-35mm f/2.8D are way too expensive. So I end up with 20mm f/1.8. Would you have any other recommendation?

If you stop down the lens to f8 in your usage, the small manual focus Voigtlander 20mm f3.5 SL II does is pretty good job for landscapes and buildings. Downsides: focussing close by astigmatism ruins the corners, and almost no software offers correction profiles for it (at least in relation to Canon FF, may be different for Nikon FF?).

 

A popular lens for Nikon is the cheaper 18-35mm, it has much better corners than the 16-35mm f2 VR. 

http://www.opticallimits.com/nikon_ff/821-nikkorafs18353545ff