Mr. Fischer described Mr. Mahan as "totally unassuming."
"Even though I would ask him a naive question, he treated me as if I was as important as anyone else. He never talked down to you," he said. "He was a wonderful friend and didn't have an enemy in the world. It was a treat to know him."
Mr. Mahan was also interested in the B&O, the Pennsylvania Railroad's Northern Central Division that operated between Baltimore and York, and the Pennsylvania Railroad.
"He loved every railroad he could get his camera next to," said his son, who added that his father's other photographic interests included lighthouses and covered bridges.
"My mother convinced him to do that," he said.
Mr. Mahan's wife of 56 years, the former Veta Arelyn Thomas, a retired Baltimore County public school principal, died in 2004.
Mr. Mahan, who had moved to the Parkville retirement community in 1999, was a member of Towson United Methodist Church.
Services will be held at 2:30 p.m. Tuesday at the Ruck Towson Funeral Home, 1050 York Road.
In addition to his son, Mr. Mahan is survived by two grandchildren and a great-granddaughter.