Get Sigma 135mm f/1.8 DG HSM Art at B&H Photo.
This series tests for extremely fine detail rendering along with the control of secondary color errors on out of focus background. If this series does not impress you, I don’t know of anything that could.
Includes images up to full resolution from f/1.8 through f/11. Diffraction effects are evaluated and shown with/without diffraction mitigating sharpening.
The D810 sensor resolution leaves much to be desired in terms of resolving power—if it had 72 or 100 megapixels, the color aliasing would be greatly reduced and quite a lot more detail should be possible. Alas.
The about $1399 price for the Sigma 135mm f/1.8 is a screaming deal that awaits a higher-resolution Nikon camera body. Were Leica to ship this lens, Leica fanboys would rave about it and it would cost $8000.
Together with the Nikon 70-200mm f/2.8E FL ED VR (the zoom that looks like medium format in its rendering), we seem to be in a golden age for DSLR lenses, so much so that I question my Sony mirrorless inclinations, particularly if Nikon delivers a D820 or whatever it will be with higher resolution and at least as good dynamic range and per-pixel quality—and an EVF option in the hot shoe would seal the deal.