Perhaps I'm missing something. If you're doing a tight head shot, and the fellow's not deformed in some way, IOW, if his head has all the features in proportion, why would there be a need to use anything but whatever lens you'd normally use? Make sure his eyes are in focus and stick with the standard 85mm - 120mm or so optic. If you've got an M 75~150 zoom, that may be a fine choice. Shoot from different perspectives, zoom with your feet as well as the lens, be sure the exposure is correct, and you'll end up with something worthwhile, both for his work and perhaps for display in his home.
Shel
