I'm using image based lighting with spherical harmonics, produced from cubemap hdr images. However there is a big problem with my implementation: Outdoor images with blue sky cause top of the lighted object become blueish. The same problem with indoor cubemaps - color of the wall transfer to the object. We don't see any top-blue humans outdoor, this blue color is neither physical nor realistic. Any idea how get rid of this problem in physically correct way ? I can decrease image saturation, but that would cause *all* light become white, I still want colored light too. Any advices, pointers to some articles ?

Sounds like your sky is too bright computationally. The sun's brightness should overwhelm the blueness of the sky. But yes, the blue sky should also give your human tops a slight hint of blue.

So make your actual lights (sun, electrical lights) relatively brighter, and decrease the image's emitting factor.

**edit: typo**

Yep, I have come to similar conclusion. Camera is not capturing enough sunlight because of limited FOV.
I think the other solution, instead of letting artist edit images manually, I can increase the weight of top hemisphere spherical harmonic. That way sun will go into mix better.
edit: May be pass image through some non-linear filer, like x**2. Make bright part brighter, and dim part dimmer, and after that average.

I'm no expert on the subject, but I'd try calibrating the sky brightness by first removing the sun from your HDR cubemap. Without direct sunlight, you now have the kind of ambient light that shadows have. And shadows can be really blue. Just don't make them too bright.