EDIT: Ron Lemen's example is actually the third picture now. It didn't appear before the edit.
This has been bugging me for quite some time. It's regarding the depiction of the blue skylight. Frankly, I'm very confused because I may be misunderstanding my sources on this.
As far as I understand from the multitude of sources I've read, the sky is a light source in a shape similar to a dome above us. What I don't understand is why there can be sky speculars and areas where its influence is greater. Not necessarily talking about the planes where the "dome of light" is unable to hit.
I've put up two illustrations demonstrating this; the third image is from Ron Lemen's tutorial and the first is from the PSG tutorial. Ron Lemen's example acknowledges the existence of skylight, but the right side of his face is conspicuously more intense. PSG's example also shows this happening but I'm pretty confused since, by theory, the yellow, green, and purple beams of light I drew in (amongst infinite numbers of it) will cause a sky specular. I've also put up a photo of this happening in real life. The sunlight hits the right side of her face but, again, skylight shows itself the most on the right side of her face. My assumption, given what I know, would be that the skylight would hit evenly across her face creating a flat form shadow across the right side of her face.
That, however, looks awful. Of course, I could just accept this idea as law and incorporate it everywhere in my drawings but I want to know what the heck's going on in fear that I might (see: will) misuse it. My first guess is that this is similar to the fresnel effect with swimming pools, where the reflection is affected depending on the viewing angle. My second guess is that somehow, somewhere in the "dome", the skylight is stronger. My third guess is that skylight isn't a dome at all. I don't want to jump into conclusions, however.
Thanks in advance.
EDIT: Messed up the directions of the light for the photo.