I have been making a hemisphere out of a UV Sphere and I noticed the shading works oddly on the poles when all faces (except the base) are smooth. A picture will probably explain better:
I can also see a similar effect (to a lesser extent) on all the faces touching the cut of the sphere.
NOTE: the part where the sphere is cut is filled with a face, so the mesh is solid.
How to properly separate smooth and flat surfaces on relatively sharp angles?