“The things we do to get them to smile,” Mr. Wunder said, then laughed. “Might be a little creepy.”

Two hours and hundreds of photos later, mock picture day was nearly done. Mr. Wunder palmed $20 bills into kids’ hands and thanked them for their good work.

He still had plenty to cover in the next three days. He would encourage psychological warfare against principals: Contact them two weeks after Lifetouch delivers its pictures, when “mommas” are complaining about poor photo quality and customer service. He would explain how to close deals with Jedi mind tricks: End a bargaining counteroffer with “Fair enough?” And he would outline the school sports industry.

Throughout the sessions, Mr. Wunder preached that school pictures are a business, not an art. But as 11-year-old Oliver Chen, a late straggler, mugged for the camera and flash bulbs went chunk-chunk, he got more expansive.

“The real reward comes when you got up on that real crisp autumn morning, and you drove across town, and you set up the equipment and you get greeted by the lunch ladies and sometimes they bring you a biscuit out of the oven,” Mr. Wunder said. “And then you see this entourage of little bodies with big smiles and little bow ties and they’re looking up to you like, ‘The picture man is here.’”

He was still in a reflective mood a few minutes later at the hotel bar, whiskey in hand. When floods and fires strike family homes, his photos are the treasures first spirited out, he said. And then, at least once a year, a car crash means the portrait he took of a schoolchild is her last. Mr. Wunder always rush-orders and frames a 16-by-20-inch photo for the funeral.

The fiercely competitive mask had slipped. Mr. Wunder sat up straighter and took a sip of his drink.