Phelps was official photographer of Yale University from 1920 to 1932. A year later he accompanied Frank Buck to India, Ceylon, Sumatra and Malaya, where he filmed Wild Cargo. While making Wild Cargo Phelps was nearly crippled by an infection he acquired after scratching himself on a poisonous renghus tree in the jungle.
Buck and Phelps were almost trampled by a herd of stampeding water buffalo.
They were spared only when the animals changed direction at the last moment. Phelps was cinematographer for some of the sequences in Buck"s 1941 film Jungle Cavalcade.
While acting as a civilian pool photographer for the atomic bomb tests at Bikini, Phelps made a documentary film of natives on Likiep Atoll. The film was selected for preservation by the Library of Congress.
Phelps died at his home in Freeport, Long Island.
He is buried in Greenfield Cemetery, Hempstead, Long Island.