Cinema4D to Arnold Workflow by DANIEL HENNIES
Here is the full tutorial by DANIEL HENNIES on Arnold rendering a photorealistic portrait in Cinema 4D with C4DtoA.
Workflows shown can be generally applied to improve skinshading on other characters. ZBrush Artist Phil Amelung provided the eyeballs, help on the texturing and facial hair creation. You need the alShader Pack by Anders Langlands to follow along. The additional assets are available to download here: uglykids.org/arnold.html