There is a big (3-foot) softbox camera left providing pretty much all the light for this photo. I say 'pretty much' because the overhead fluorescents are on... but not really doing anything for the photo.
Looking at this after the fact, I realize that I should have crouched down a little bit to get rid of the ground, since you can't see the subjects' feet anyway... Oh well.
These three gentlemen were very cooperative in setting up everything to make the picture work, and the studio we shot in was amazing.