Here are four tests I made to test natural lighting in povray.
Modelled in blender, then exported to povray using povanim.
I think, early afternnon and night are fine. The others lacks shadows… 
Exquisite images. I must especially congratulate you on the ‘night’ scene. It is almost photographic.
The daytime images seem a little over exposed in comparison. Maybe the ambient values are too high. Another thing I notice is that the furniture has almost no shadows on the floor, in the day-time shots. That could be one of the problems.
I would love to see a walkthrough on how you created that night time image - from povanim export to lighting to final povray render. I always feel you can’t have too many tutorials on lighting. People seem to cover modelling quite extensively, but lighting is more challenging and more important in most cases.
Looking forward to seeing more of your work, and hopefully a tutorial. 
Aww Love the night scene! I can just imagine the feel of those vinyl/leather chairs
Night scene looks very real
I made little improvements in day scenes. Now I’m using trick with saving povray radiosity data, and rendering time is few times lower then before, with more details
It’s hard to get more shadows because of big window at front.
bump it back up totally killed your night scene - edges are very jaggy in all scenes
and the mirror on the night scene window is way to much
The objects in the room would have soft shadows, due to the main light source being the window and the daylight being reflected around the inside of the room. There are enough shadows present in the new daytime and night time renders, but the others need the objects to have more shadow.
There looks to be enough shadow present from the room, it’s just the objects’ shadows that I think need tweaking. Maybe you can use a softer version of the shadow map from the new daylight scene.
Sonix.
Nice test!
There seems to be a problem with your recursion limit in the radiosity block in POV-Ray in both images.
The ceiling in both cases doesn’t seem to participate to the lighting of the scene in “early afternoon”, “late afternoon” and “cloudy sky”.
Tha tappears particularly in “early afternoon” where the square of light on the floor doesn’t seem to affect nearby furniture!
So increase the recursion and see what happens. I warn you in advance rendertime is going up from here^ 
Jean-luc: your question, my answer
interesting experiments
excelent lighting
hi,
i don’t agree with the others, that the lack of shadows is the problem. in such scene with no direct but only very diffuse light there are no “real” shadows. you just have to look around in your own home. same for mirror in window. it looks like that in real life. we are just used to filter unimportant informations when we look around. looking at a picture (especially when we know it’s artificial) that contains these informations often makes it feel strange.
but still i share the feeling that in these two daylight images there is something wrong. i would suppose, that it’s the exposure of the image. everything is too bright. a room in these lighting conditions must be much darker in the corners or e.g. in the back of the sofa. as i work with radiance i would suggest to change the exposure - maybe thisworks in povray too. i nradiance you can do that even after the image has been rendered, cause it stores specific values.
that are my thoughts - don’t know if i’m right.