Thank you for including this very effective "environmental" portrait. Since many pottery workshops have rather poor lighting, I hope you will describe the windows/skylights/reflectors(?) used in this image.
The round blue thing behind his arm appears to be in sharper focus than his face... I wonder if the focus was missed? I really like to see sharp focus on the face in a portrait, most essentially the eyes, but in this case (given the equal distance of all of his features) his entire face should be in focus.
I really love this picture, but I just don't see any possible way that it uses natural light only. If nothing else, it seems like the lights in the studio are on.