After the war he began making documentary shorts, directing and photographing industrial and commercial films.
Decaë first worked as a cinematographer with Melville on Le Silence de la Mer (1949).
They had been lucky as Decaë was finding it hard to get work at that time as he was being informally shunned by many after participating in a critical film about the Korean War.
By the time Decaë worked for François Truffaut on The 400 Blows he came with a reputation, which meant that he was the highest-paid person on the film.
He made the New Wave possible, backing up Melville, Malle, Chabrol and Truffaut."