The Bahamas was his birthplace. Born Bert Cooper, he was one of eight children. He moved to New York when he was a teenager. He intended to study engineering, but fell into acting instead, studying with Uta Hagen.
A storybook version of his discovery has been circulated, in which Mr. Lockhart, driving a taxi to support himself, picked up playwright Ketti Frings, who was impressed by her driver. Whether he was found in this manner or not, Mr. Lockhart was cast in the 1960 Broadway play The Cool World, about life in blighted urban Harlem.
Unable to find work in the U.S., he moved to Italy in the '60s to form his own theatre company, then to Germany, and finally to England, where he worked with the Royal Shakespeare Company in Stratford and found roles in British films. When he moved back to the U.S., he found a place as a leading personality in the "Blaxploitation" film movement of the early '70s. His film roles from this period include "Joanna," "Cotton Comes to Harlem," "Halls of Anger," "Melinda," and "Let's Do It Again."
He returned to Broadway in the short-lived 1980 musical Reggae.
Mr. Lockhart moved back to The Bahamas in the late '90s. "Calvin had wonderful range as an actor," Sidney Poitier told The Los Angeles Times. "He really had such enormous promise. I don't know why he was not more utilized, because he was so good. As a matter of fact, he had movie-star qualities. He was a very handsome man, his impact on the screen was striking and his work was highly praised."
In addition to Jennifer, his fourth wife, Lockhart is survived by two sons, Michael Cooper and Julien Lockhart Miles; a daughter, Shari; his mother, Minerva Cooper; three brothers, Carney, Eric and Phillip Cooper; and two sisters, Delores Bain and Melba Styles.