I am new to blender and have recently created my first model. I created the mesh and then textured it, added a world environment texture, and rendered it only to find a very dark harsh "shadow" around the rear of my model. However, the shadow only appears when I add a face to the back of the model to complete the whole mesh. I have included pictures so you can see what I am talking about.
Without the rear face
With the rear face
In the first picture you can see the model's cylindrical body WITHOUT it's rear face resulting in no shadow. However, in the second picture, a face was added to the rear of the model resulting in a harsh shadow as shown.
I am using blender version 2.73