Lars E. Janson, 79, a retired Federal Trade Commission lawyer whose avocation was photography, died of pneumonia June 10 at the Fairfax Nursing Center. He had Alzheimer's disease.

Mr. Janson's professional career began in 1950 as an associate at the Washington law firm of Covington & Burling. He joined the Federal Trade Commission about a year later and became an attorney-adviser in the Washington field office.

He also did work in mergers and acquisitions but spent most of his career at the FTC in the field of anti-monopoly law, retiring in 1972 as special adviser to chief of the Bureau of Restraint of Trade.

In retirement, Mr. Janson turned his energy and attention to photography, crisscrossing the country with camera equipment in tow.

He attended photography workshops on image quality, darkroom techniques and composition including a class taught by renowned landscape photographer Ansel Adams.

Mr. Janson held leadership positions in photography organizations and entered his prints--western and urban landscapes--in local and international competitions. His works were showcased in solo exhibits and as part of largers ones at the Factory Photo Works gallery and in the Art League in the Torpedo Factory in Alexandria.

He was vice president of the Northern Virginia Photographic Society and a member of The Group, which consisted mainly of professional photographers.

Mr. Janson was born in Washington and grew up in Arlington, where he graduated from Washington-Lee High School. He graduated and received a law degree from George Washington University.

Since 1951, he lived in Alexandria and was active in civic organizations. He helped organize the Hollin Hills Neighborhood Watch Program and was its co-chairman. He also served on Fairfax County citizens committees and was a member and a deacon of First Baptist Church in Washington.

Survivors include his wife, Kathryn G. Janson of Alexandria; two sisters; and a brother.