I proceeded to fix those things. Light colors got desaturated and even turned slightly blue. The light coming from the sky was now almost gray.
The lack of specular on the street was fixed by duplicating the main light, turning off Affect Diffuse option, and using the Place Highlight tool to position it in the right spot (Fig.15). Fake? Sure, but looks good, and I couldn't achieve it with the main lamp placed where it's placed in the scene. If it was a real life movie set, it would probably be handled in a similar way by placing a light source just so.
The whole composition was starting to look unbalanced, gravitating towards the right side. I therefore added a light in the doorway down on the street level to the left in order to balance it a bit. There's also an angled box, invisible to the camera, shaping the hotspot to resemble an open door - yet another trick here (Fig.16).
The walls were turned into a Shellac Material, with a VrayMtl in the shellac slot (Fig.17). After some tweaking, I achieved a nice looking, damp wall, catching the highlight from that little square window.
The image was starting to look quite good now but a few tweaks were still required. The metal railings needed a reflective VrayMtl, the little metal roof high above the street needed to look wet, too. But the main problem was my 'preview' windows. I solved that by turning the lights to be single sided, and duplicating them. The duplicate is way weaker, as it serves only to illuminate the wall recession around the window. Now what's behind the window is another fake - it's simply a self-illumination map, using a photo of a window from the outside, at night (Fig.18). It'll do for a still image, but it won't hold up for camera movement - we would need at least some simple interior then. Fortunately we are working with a still this time.
A few more slight tweaks remained - I constantly find something to tweak, even if those things are too small to write about, they are always there. Change the hue here, by a tiny bit, tweak the material there, that kind of stuff. When that's done, we can try to finally render the image at higher resolution. This scene is quite time-consuming to render, due to the fog - overnight is a good idea. For test renders, I use low resolution, fixed image sampling, and lowered subdivs in the fog.
Again, note of caution - Fixed sampling produces a lot of bright noise in specular areas appearing as though there should be nice, crisp detail when you do a full render. Much of this disappears and gets filtered down and smoothed, providing a much softer looking result in the end. This is something to bear in mind and so be prepared to do more than one higher quality render. The image took 22 hours to render, but I used a 3-year old machine.
Most of the post-production I had already sorted out, throwing my test renders into that first PSD test-image. I used a few radial gradients to enhance the atmosphere, some color corrections to bring back the cold, blue hues, upping the gamma a bit, overlaying some photographic smoke images, some subtle chromatic aberration - simple things, really, but as always, crucial to a good looking image. (Fig.19) shows most of the things I added. The final image is on (Fig.20).
I'd like to point out that this image does not use GI. Sure, it wouldn't do any harm but it works quite well even without it, mainly due to the fog which adds some bright fill to the scene. Apart from this it's nighttime whereupon the bounced light is way weaker than during the daytime (no sun, no bright sky).