Get Sigma 135mm f/1.8 DG HSM Art at B&H Photo.
This series looks at the entire aperture range from f/1.8 through f/16. Of interest are peak micro contrast at f/1.8 as well as how well f/11 and f/16 hold up with diffraction mitigating sharpening.
Includes images up to full resolution from f/1.8 through f/16. Diffraction effects are evaluated and shown with/without diffraction mitigating sharpening.
This series and the American Hotel wail in protest for a 72 megapixel Nikon D900. I speak not of just resolution per se (surely a shortcoming of the D810), but also of sidestepping color aliasing and spurious resolution and color purity and similar digital limitations of a Bayer sensor that result when using extremely high quality lenses (presuming that resolution is only resolution is an fundamental conceptual error—see oversampling).
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. The performance here is better than any Leica M APO lens in resolving power and vastly better in terms of color correction. How Sigma can give make a lens this good at this price is surely intimidating to other companies.
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.