James Robert Dunlop, 74, a former special agent in the FBI who in 1946 founded his own photographic studio and processing laboratory in Washington, died of cardiopulmonary arrest Sept. 3 at Sibley Memorial Hospital.

Mr. Dunlop, who lived in Chevy Chase, was born in Baltimore. He attended the University of Maryland there and became a photographer at its medical school.

In 1935, he moved to Washington as a photographer for the FBI. He was appointed a special agent and remained with the organization until he resigned to go into business for himself. He attended George Washington University.

His first company was James R. Dunlop Inc., which he started with his wife, Marcella (June) Dunlop. At its beginning, it did both studio work and film processing. In 1966, the Dunlops were joined by Frank Davis and they formed Davis-Dunlop Inc. This specialized in studio photography while the laboratory work remained with the original firm.

Mr. Dunlop also started Photo Techniques Inc., an equipment business. He was president of all three corporations and his wife was vice president.

In addition to running these concerns, Mr. Dunlop made several trips abroad on various photographic assignments. For reasons of health he had reduced his activities in the past few years and he and his wife of 43 years were in the process of closing out their business activities.

Mr. Dunlop was a member of the Kiwanis Club of Washington, the University Club, the Columbia Country Club and the Society of Former Special Agents of the FBI.

In addition to his wife, of Chevy Chase, survivors include a sister, Mary Louise Dunlop of Baltimore.