What is the problem with my bump mapping? I am trying to map a high resolution bump map on a UV sphere, I am using a UV map, and I get this result:



What causes the renderer to make these huge blobs? This should be a moon, far away and big (distance is about 500, size is 300 blender units), my bump map is 3840 x 2160  Pixels TIF file (I got the same result with a half resolution bump map, too), UV-mapped to the sphere. Mesh is set to smooth, Subsurf is set to 4 subdivisions, and the node setup is as follows:



Mapping (if I map the bump map to the color of the diffuse shader, it does not get pixelated):


What am I doing wrong?

Thanks for the help.
I have figured it out.
The subsurf for rendering was accidentally switched off when baking the bump map.

Thanks for all your inputs!