Born Johann Jacob Altmann in Sopron in what was then Austria-Hungary, the town in actually located in Hungary. His father Sam had actually immigrated to the United States in the 1880's and had changed his last name to Alton, but returned to Hungary and changed his name back to Altmann. Johann himself came to the US in 1919 to live with a wealthy uncle in New York, so he could attend college. He got into the motion picture industry by being grabbed off the street as he was passing by Heart's Cosmopolitan Studio's on 2nd Avenue. A gateman approached him and proclaimed "you are just the man we are looking for." He was then made a dress extra and appeared next to Marion Davies and paid $12.50 for the part (no one seems to know which film this was). This gave him an instant film bug and he promptly ended his involvement with academics.
He most likely moved to Hollywood in 1923. What is known is that by 1924 he landed a job at MGM as lab technician. He was a work your way up through the ranks kind of man. When Paramount offered him a job as cameraman, he jumped at it. This is when his only silent era credit comes, with going to France with Ernst Lubitsch to film backgrounds for Lubitsch's The Student Prince In Old Heidelberg (1927). It is around this time he claimed to discover Maurice Chevalier. In 1932 in left for Argentina, where amongst shooting Spanish language films there, he also designed the that countries first sound studio. He returned to the US in the late 1930's and worked as a cinematographer in B-Noir movies. He then went one to be most sought out cinematographers in the business. In 1951 he won an Academy Award for his shooting of the ballet sequence in An American In Paris, the first Hungarian born person to do so. He also penned a book about the shooting of films in 1949, one of the first cinematographer's to do so. He also served for the US in World War II.
He passed away on the 2nd of June 1996 at the age of 96.