Screw Modifier Darker Shading on Half of Object I'm trying to create a spherical object using a screw modifier on a mesh created using a mirror modifier.

The first screenshot shows my mesh created by applying a mirror modifier over the x axis.



The second screenshot shows the screw modifier applied.



The problem is the split in how the upper and lower halves are shaded (darker on top). Is there a way to fix this?
I think the issue may be that your normals are flipped: In 3d each face has a 'normal' that represents which way the lighting should be interpreted. To fix this, in edit mode press CTRL + N. This will try to flip the normals so they point outwards. If this does not fix it, open your toolshelf and look to the Operators menu at the base of it (Looks like this). Check the box saying 'Make normals consistent inside'.