thanks guys
the heavy shadows are done by the clouds but I increased the contrast of the render in postwork,
because it was not as good in the raw render.
And, working in black and white, I change the blue value of the sky to the darkest point possible,
trying to keep a kind of depth, if I might say, in the clear part of the sky.
It works pretty well, for a wip on my screen but I am not sure it would be a good render
on a screen with, for example too much gama .
Anyway, I am still working on that one right now,
and I might lose that kind of feeling in the "final"version, considering it will be in colours
Cheers !