It was my first Rendering in Indigo back to v0.5 > v0.6
(I like the vignette very much!)
Now I did a new approach, using Indigo 0.65 take a look:
I shoud have tweaked Rainhard & burn option s much better,
but after rendering for 15h on 2 machines (1640 muts per Pixel) its to late
So I did some Post Prozessing by using a Ambient Occlusion Layer done by C4D,
a Depth Layer for (minimal) DoF (and one to kill the not smoothed normals in the BG Wall)
and some color & level correction, denoising, sharpen & Stuff...
the Horizon Line Bug can be seen here too...
Sorry for the big pictures, I couldn'resist
*** EDIT ***
I've redone the composition, with after 22h rendering with 2180 Mutations per pixel, better color correction,
better denoising and slightly more DoF (cabel) check it Here