Water reflections-like spots on walls - Yafray

I’m looking for an natural lighting of an interior scene. Maybe indigo is better but i have no such a patience for this image to be rendered completely, so i gave a try to yafray. After a few hours of experiments i managed to find an light/exposure/gamma combination that gives me a satisfying result in terms of light intensity. But, there are some spots on the walls I don’t know where from.

It’s Yafray engine with Gamma=2, Exposure=4, Raydepth=5.
The material is a plain white Reflection=0.5, Specularity=0; Ambient=1

Does anybody encountered this before ?
Thanks in advance!


Mea culpa, wasn’t searching enough.
The answer is here:

Just have to increase the quality level of the rendering.

It has been here few times, have you read this: http://blenderartists.org/forum/showthread.php?t=111239 ?

OK, you found it sooner than I typed this…

Thanks for the links!

this thread will also help:

Thank you for your answers.That was quick!
Anyway i made another render (different scene) with Method:Full and Quality:Best and

The noise is less visible, but nevertheless annoying! Got to dig a little further into the docs.