When I walk on an asphalt road on a summer day and I look below me ( where I set my feet ) the area around my feet appear to be lighter than the area a few meters away. I think I notice the same with brick walls. They appear to be darker to me at grazing angles. But all theory I can find and what I experience in blender is that when you increase the roughness of a material, and/or you play with Fresnel the materials created in blender show a lighter color at grazing angles. See also the youtube videos about physically based rendering from CynicatPro at https://www.youtube.com/playlist?list=PLlH00768JwqFtFtsTKBxnLwadWsNo36R-
I started to think that glossy materials might appear lighter at grazing angles and rough materials darker, but I am sure my theory is far from correct. I hope anyone can tell me more about it. Is it maybe that the bumpiness caused self shadowing when it comes to materials like roads and walls, and so they appear to be darker at grazing angles ?