O. G. Mason is best remembered, however, for his clinical medical photography accomplished during his forty plus years at Bellevue Hospital. He was frequently called upon to provide illustrations for monographs published by leading physicians and surgeons associated with the hospital and its medical college, including Lewis Albert Sayre, John Call Dalton, and Francis Delafield. His most notable photographs appeared in the great photographic dermatology atlases written by George Henry Fox.
O. G. Mason is primarily recognized for his clinical medical photography, which he executed over a period of more than forty years at Bellevue Hospital. He was often asked to create illustrations for monographs authored by prominent physicians and surgeons affiliated with the hospital and its medical college, including Lewis Albert Sayre, John Call Dalton, and Francis Delafield. His most celebrated photographs were featured in major dermatology photo atlases written by George Henry Fox.