The Physical Sun & Sky is built around Mental Ray, so overall learning about how to create rough lighting for scenes, over even a final lighting set-up for a scene, this render can be really handy.
|How to get the Physical Sun & Sky|
It worth noting that this function is directly linked to Mental Ray, if Mental Ray is not active, then you cannot use Physical Sun & Sky.
|Red & Blue Shift (Blue)|
|Red & Blue Shift (Red)|
|Sun & Sky Pointing at Camera|
|Final Image Mixdown|