Shamroy was educated at Cooper Union (1918), City College of New York (1919–20), and Columbia University (where he studied mechanical engineering).
A product of a practical-minded family, young Leon often worked after school in one of his uncle's offices as a junior draftsman.
In 1920, he joined them at the Fox lab to help with the laboratory work and went on to spend thirteen years as a struggling technician.
Another film, Blindfold (In the Fog) attracted the attention of Hollywood, some of whom described Shamroy's camerawork as "worth its weight in gold."
Around this time, Shamroy went to Mexico where he worked for Robert Flaherty on a film called Acoma, the Sky City, a story about an ancient Indian tribe.
After his brief stint at Columbia, Shamroy worked for Jack Cummings, Louis B. Mayer's nephew, on a series of MGM parodies of the famous screen epics, starring dogs.
In one of the films, So Quiet on the Canine Front, the dogs were so realistic that when they were shot down the Humane Society was enraged.
He and the crew were terrified when a fourth-class passenger on the ship they were sailing on, the Empress of Canada, ran amok and stabbed thirty people to death two days out of Yokohama.
Years later, while working on a picture called Crash Dive (1943), he learned that the star, Tyrone Power, had experienced the same shipboard horror.
He made films in places as far distant as the Dutch East Indies, Bali, Samarai, and Batavia.
In a loan to Columbia, briefly his employer in the previous decade, Shamroy used zoom lenses on Private Worlds (1935), directed by Gregory La Cava, long before they were commonly used.
This was a film about mental illness, and the zoom lens was especially effective on the scene where Big Boy Williams, a patient, goes berserk.
With his talent and abilities now recognized, Shamroy landed a job through Myron Selznick at 20th Century Fox, where he remained for the next 30 years.
With 5,000 people in the blaze of light and hundreds of flags flapping, the re-creation of the Baltimore Democratic Convention of 1912 was a most startling shot on the screen.
She had kind of a fantastic beauty like Gloria Swanson, and she got sex on a piece of film like Jean Harlow.
The real art of cinematography lies in the camera's ability to match the varied moods of players and story, or the pace of the scene.
"[citation needed] Shamroy was notable for being gruff and short-tempered, regularly clashing with directors Rouben Mamoulian, John M. Stahl, and Otto Preminger.
[6] He once claimed that Lee Garmes "will never see the day that he's as good as I am and that goes for anybody in the motion picture business", implying that he saw himself as better than any other cinematographer.
On November 1, 1925, he married Rosamond Marcus, who gave birth to his son, Paul Shamroy (August 24, 1926 - May 12, 1969).