Hey lolec, don't get me wrong, I DO love the Corona renderer!
Totally. And I could praise its 90% fantastic features 24/7. :)
However, let's get back to our light mapping / color grading topic this thread had started with.
After having rendered tens and tens of white empty interiors with parquet floor, this showed me quite clearly where the small but very significant things lay, which make renders often look somehow lame, dull and as if your eyes simply cannot focus on anything in the pics:
1. light-dark transitions on surfaces ( e.g. room walls ):
with "usual" HC-values ( 1+ ), those transitions get very washed out. ( To avoid that I arrived at 0.7 - 0.6 as may standard setting for HC. )
Same effect (dull image) , although by far not so strong, when Filmic Highlight is used.
Filmic highlight should behave a bit differently from how it does at the moment. Currently it softly clamps the highlights but also brightens the mids / darks. Result: transitions on walls / surfaces again get dull.
In my opinion, filmic highlight should do the soft clamping ONLY on the highlights... leaving the mids & darks unaffected. So you don't lose the subtle contrast which you never get back by brutally cranking up contrast values.
2. The correct proportion between lit surfaces and those in the shadow.
On this point I will not philosophy too much.
If one uses HC 0.7 - 0.6 this seems to be quite okay.
HC 0.7 - 0.6 seems to also be the answer to my first point (transitions)... and it could work fine if filmic highlights behaved like proposed in point Nr. 1.