Working the light for a chiaroscuro effect in black and white

This is a scene I photograph quite often, mostly in the late evening around sunset or afterwards into the night.

I had been observing the light change for awhile, as the sun moved further into the southern horizon. I wanted this to be a photo of the Flatiron District with the Flatiron Building playing center stage in the composition. At 10:30AM the building was fully lit from the morning sun, which also left a pleasing shape of light at its foot. I felt the way the light fell on the city at that time would make an interesting black and white image with a composition built upon dark contrasts of light and deep shadow.

I felt the photo is a little difficult to see at this size so I included a high res version, which can be downloaded here. It isn't as big as the final 40" wide image, but is big enough to give a sense of detail. 

Even though the Flatiron Building is the main focus, my favorite part of the scene is off to the left where the sunlight bounced off of a building to light up the Metropolitan Life tower and clock.

The dark areas of the scene were as important as the lit areas in terms of the compostion so I didn't know in advance what focal length lens I would want to record the scene. I settled on putting the 24-120mm Nikon f/4 zoom on a Nikon D810. The zoom gave me some quick mobility to bracket around the focal lengths, and the f/4 didn't bother me because the photo was going to be taken in very bright sunlight and I could pick my aperture.

I added a polarizing filter to both darken the deep blue sky and cut through the haze in the distant building. Even so, with an ISO of 100 I ended up at f/5.6 and 1/250 of a second. While you could hand hold a camera at that speed, I have learned the hard way that it is best to put a high resolution  camera like the Nikon D810 on a tripod at all times. High resolution seems to magnify motion blur.

In post processing I pushed the contrast even further to increase the chiaroscuro effect and added a vignette for the same reason but also to focus the attention at the center of the scene.